HomeMy WebLinkAboutTDX Power, Inc - Manley Hot Springs Geothermal Plant Final Report - Jan 2010 - REF Grant 2195421
WILLOWSTICK
GEOPHYSICAL INVESTIGATION
Of:
MANLEY HOT SPRINGS
GEOTHERMAL RESOURCE
Manley Hot Springs, Alaska
For:
TDX Power, Inc.
4300 B Street, Suite 402
Anchorage, Alaska 99503
Contact Representative:
Roger L. Bowers, P.G.
Geological Consulting Services
1305 Bell Avenue
Ely, Nevada 89301-2094
Prepared by:
Willowstick Technologies, LLC
11814 S. Election Road
Suite 100
Draper, Utah 84020
USA
(801) 984-9850
Willowstick Project Number: 09091
Manley Hot Springs
TABLE OF CONTENTS
i. Executive Summary ............................................................................................................4
1.0 Introduction .........................................................................................................................6
1.1 General ............................................................................................................................6
1.2 Background .....................................................................................................................6
1.3 Purpose of Investigation .................................................................................................7
2.0 Approach to the Work.........................................................................................................8
2.1 Work Plan .......................................................................................................................8
2.2 AeroMag Investigation ...................................................................................................9
2.3 RaMPS Investigation ......................................................................................................9
3.0 AeroMagnetic Survey .........................................................................................................9
3.1 General ............................................................................................................................9
3.2 AeroMag Results ..........................................................................................................10
3.3 AeroMag Data Inversion Model and Interpretation......................................................13
4.0 RaMPS Survey ..................................................................................................................14
4.1 General ..........................................................................................................................14
4.2 RaMPS Data Results and Interpretation .......................................................................15
5.0 Summary of Investigation and Recommendations ...........................................................18
5.1 Summary of Results ......................................................................................................18
5.2 Recommendations .........................................................................................................19
6.0 Disclaimer .........................................................................................................................20
6.1 General ..........................................................................................................................20
Appendix A – Helicopter Aeromagnetic Survey Report ..............................................................21
Appendix B – White paper (RaMPS Technology Explained)......................................................43
Appendix C – Professional Biographies .......................................................................................56
2
Manley Hot Springs
FIGURES
FIGURES
Figure 1 – Project Location
Figure 2 – Site Map and Area of Investigation
Figure 3 – Reduced-to-Pole (RTP) Magnetic Intensity Map
Figure 4 – Close-Up Map of Anomalous Zone
Figure 5 – 3D Inversion Model with Low Magnetic Susceptibility Anomaly
Figure 6 – Layout of RaMPS Survey Lines
Figure 7 – Line B Resistivity Pseudosection and Location Map
Figure 8 – RaMPS Data Slice showing Apparent Resistivity Contrast
Figure 9 – Proposed Drilling Targets A and B
3
Manley Hot Springs
i. EXECUTIVE SUMMARY
This report presents the results of an AeroMag investigation and a Willowstick® Resistivity
Monopole Profiling and Sounding (RaMPS) survey to help characterize the extent and depth of
the Manley Hot Springs geothermal resource. The AeroMag data, acquired by EDCON-PRJ,
Inc. was provided to Willowstick by TDX and was utilized to help plan and lay out the RaMPS
survey lines.
The integrated analysis of both the AeroMag and RaMPS data provided valuable insight in
characterizing the geothermal resource and adjacent structures. Both datasets indicate that the
source of hot water lies deep in an area southwest of the known hot springs, and that it wells up
to a shallow aquifer as it makes its way toward the known surface expressions.
The RaMPS data define a sharp contact between high and low resistivity zones along the
northwest boundary of the geothermal resource, thereby marking the most likely location for hot
water, which is adjacent to the contact zone. Accurate delineation of the resource itself, given
the RaMPS data alone, is somewhat obscured due to difficulties encountered in achieving
penetration on lines running near and along Hot Springs Slough. In conjunction with the
AeroMag data, however, the resource can be characterized more accurately.
To interpret the AeroMag information, Willowstick subjected the data to a rigorous and powerful
inversion algorithm designed to provide accurate depths to anomalous sources. The resulting
model of anomalous magnetic susceptibilities revealed a strong magnetic low anomaly
originating from depths greater than 1,000 feet in an area southwest of the known hot springs.
This anomaly is believed to represent the zone of hydrothermal alteration where the hot water
has altered the magnetite mineral in the rock. Moving from the deep resource toward the hot
springs to the northeast, the alteration zone rises to depths within 600 feet. A little further to the
northeast—approximately 1,000 feet before reaching the surface expressions—the anomaly
terminates abruptly, signifying that the hot water has risen and cooled to the point that it no
longer alters the magnetite mineral in the rock.
Based on careful analysis of the AeroMag and the RaMPS data, Willowstick has located two
proposed drilling targets, labeled A and B, to intercept hot water in the geothermal resource
before it cools (see Figure i).
4
Manley Hot Springs
Figure i – Map of Proposed Drilling Targets
5
Manley Hot Springs
1.0 INTRODUCTION
1.1 General
This report presents the results of an AeroMagnetic Survey and a Resistivity Mono-pole
Profiling and Sounding (RaMPS) geophysical investigation of the Manley Hot Springs
geothermal resource. The purpose for the investigation is to help identify drilling targets
wherein the geothermal resource can be proven and possibly developed into a low-cost
renewable electrical energy resource for the community of Manley Hot Springs, located in
central Alaska (see Figure A). For full sized versions of figures in this report, refer to the
Figures Section.
Figure A – Manley Hot Springs, Alaska Location Map
1.2 Background
Manley Hot Springs is located about 145 km northwest of Fairbanks and 71 km east of the
village of Tanana on the Yukon River. State Highway 2, known as the Elliott Highway,
connects Manley Hot Springs with Eureka, Livengood and Fairbanks along a 260-km road.
Manley Hot Springs lies at the base of the Manley Hot Springs Dome—a local elevated area also
known as Bean Ridge—adjacent and parallel to the Tanana River Valley (see Figure B).
6
Manley Hot Springs
Figure B – Manley Hot Springs Area Map
The first non-Indian settlement at Manley Hot Springs was established in 1881 as a trading post.
The trading post eventually transitioned into supporting mining activities as a result of the
discovery of gold in the area in 1898. Historically, the geothermal resource—around which the
community was built—provides water for drinking, bathing, irrigation and heat (i.e., homes,
barns and green houses). Today, the community consists mainly of a few homes and small
businesses with various recreational outdoor opportunities (fishing, hunting, dog sledding, etc.).
A diesel generator provides electrical energy for the community. Because of the community’s
remote location, very little is known about the Manley Hot Springs geothermal resource with the
exception of that observed within a few meters of the ground’s surface.
1.3 Purpose of Investigation
Because of global environmental standards, cost of electrical energy produced from traditional
fossil fuels, and the mounting desire for green power, the geothermal industry is experiencing
enormous growth, especially given that new technologies can utilize low-temperature geothermal
water to generate economical electric power. As a result, TDX Power, Inc. (TDX), a leading
energy generation and service provider for the State of Alaska has expressed an interest in
possibly developing the geothermal resource into a small, low-cost renewable electrical energy
supply for the community of Manley Hot Springs. TDX contracted Willowstick Technologies,
LLC (Willowstick) to help identify drilling targets from which the geothermal resource can be
proven and possibly developed.
7
Manley Hot Springs
2.0 APPROACH TO THE WORK
2.1 Work Plan
Due to the size of the study area, budget constraints, and the need to accurately and cost-
effectively evaluate the geothermal resource, a two-phased approach was employed to
characterize the geothermal resource. The two-phased approach consisted of: (1) an
aeromagnetic survey (hereafter referred to as AeroMag); and (2) a resistivity mono-pole profiling
and sounding (or RaMPS) survey.
The AeroMag investigation was targeted to provide a general reconnaissance of the geothermal
resource and surrounding study area (see Figure C). The RaMPS survey was designed to be
more site-specific and was targeted for smaller areas that warranted additional investigation after
having performed the AeroMag survey.
Figure C – Manley Hot Springs Study Area
The two phases of fieldwork required the services of two companies who specialize in different
types of geophysical investigations. EDCON-PRJ, Inc. (EDCON) was contracted to perform the
8
Manley Hot Springs
AeroMag survey (Phase 1 work), and Willowstick Technologies, LLC (Willowstick) completed
the RaMPS survey (Phase 2 work).
2.2 AeroMag Investigation
The purpose for the AeroMag survey is to map local changes in earth’s natural magnetic field
over the Manley Hot Springs study area, revealing the magnetic susceptibility of the subsurface
rocks—a property that indicates the amount of magnetically susceptible minerals (primarily
magnetite) in the rock. This geophysical survey methodology has been used for many years in
characterizing subsurface geologic structure and areas of active geothermal activity. Hot
geothermal fluids can cause a gradual decomposition of magnetite through a process called
hydrothermal alteration, causing anomalous lows in local magnetic field measurements.
The least expensive and quickest way to acquire the necessary AeroMag data (in this case over
the Manley Hot Springs study area) was to perform the survey via airborne platform flying at
low speeds and low altitudes while measuring the magnetic field intensities. Appendix A
contains EDCON’s report on acquisition of the Aeromagnetic Survey. The interpretation of the
AeroMag data itself, including an inversion model, is covered in this report.
2.3 RaMPS Investigation
The purpose for the RaMPS investigation is to evaluate the geothermal resource from a different
perspective by identifying the contrast in subsurface electrical properties which can be used to
characterize the geothermal resource. Resistivity measurements in general are very sensitive to
geothermal activity because the high-temperature water increases the electrical conductivity of
the rock and soil through which it permeates. Careful interpretation and comparison of the
RaMPS data along with the AeroMag data is recommended to help identify drilling targets from
which the resource can be proven. A test well should be drilled into the main flow of geothermal
water as it flows up from depth in order to fully determine its maximum temperature and
production flow rate.
Because the RaMPS data acquisition is more labor intensive than the AeroMag survey and
because it involves access issues, the RaMPS survey was applied only to specific areas of
interest—identified based on the AeroMag investigation—to obtain additional information about
the subsurface resource.
3.0 AEROMAGNETIC SURVEY
3.1 General
During the period of July 18th through July 24th, 2009, EDCON completed their contracted
Helicopter Aeromagnetic Survey over the Manley Hot Springs geothermal study area (Phase 1
work). Figure D shows the survey coverage area and flight paths employed for the investigation.
9
Manley Hot Springs
Figure D – AeroMag Coverage and Flight Path Grid Layout
Northwest-southeast primary survey lines were spaced at 100-meter intervals. Northeast-
southwest tie-lines were spaced at 500-meter intervals. A modified drape program was flown
with a nominal helicopter terrain clearance of 150 meters above ground level. This resulted in a
nominal magnetometer sensor height above the ground of approximately 125 meters. Roughly
500 line-km total were flown to insure good data coverage of the study area.
3.2 AeroMag Results
Figure E presents the results of the AeroMag survey. The data have been processed by a
correction method called reducing-to-the-pole (RTP), which simplifies interpretation by
eliminating distortion due to the tilt of earth’s magnetic field.
10
Manley Hot Springs
Figure E – Magnetic Intensity Map
In this map, the purple shading represents magnetic intensity highs while the dark blue shading
represents magnetic intensity lows. Keep in mind that these data were acquired over a large area
to enhance the general picture or understanding of the geologic structure around the Manley Hot
Springs area. The coverage and quality of the data are very good and show some highly
interesting features.
The magnetometer used in the investigation is extremely sensitive and can detect small changes
in the distribution of magnetic minerals in the subsurface rocks. Magnetic highs indicate a
11
Manley Hot Springs
greater amount of magnetic minerals, while the lows indicate a lesser amount of magnetic
minerals in the subsurface. At geothermal sites, magnetic low anomalies can be an indicator of
magnetite destruction through alteration by hydrothermal fluids.
The AeroMag data (Figure E) clearly highlight the transition from the Tanana River Valley
sediments to the Manley Hot Springs Dome comprised of igneous intrusive material. This
contact zone is marked by the steepest gradient (yellow shading is a good indicator) in the
contoured AeroMag data. This geologic contact feature may also include a fault. In most cases,
igneous rocks contain more magnetite than sedimentary rocks, but note that the opposite is true
here based on the AeroMag data. The river valley sediments to the southeast have a higher
magnetite content than the igneous rocks comprising the Manley Hot Springs Dome to the
northwest.
A major magnetic low (shaded dark blue) is located southwest of the Manley Hot Springs area.
Because this anomaly is much lower even than the signature of the granitic pluton, it is a
suspected indicator of hydrothermal activity that has altered the minerals and decomposed the
magnetite beneath this area. At the northeast terminus of this magnetic low, a protruding portion
of the high magnetic susceptibility material abruptly cuts off the low anomaly. Figure F shows a
close-up view.
Figure F – Close-up of Northeast Terminus of Anomalous Zone
The data suggest that a source of geothermal water probably originates southwest of the surface
expressions. Looking at the magnetic field map, however, it is difficult to determine with any
degree of certainty the depth of the anomaly related to the geothermal resource. For this reason,
12
Manley Hot Springs
Willowstick created an inversion model of the RTP AeroMag data to estimate the resource’s
depth. The model area is outlined (black dashed line) in Figure F.
3.3 AeroMag Data Inversion Model and Interpretation
The AeroMag data and magnetic intensity map were submitted to TDX in early August 2009 by
EDCON. This information was then forwarded to Willowstick for further analysis and
modeling. Willowstick analyzed the AeroMag data and subjected it to a rigorous inversion
algorithm (mathematical model) designed to predict the magnetic susceptibility in a three-
dimensional space based on the magnetic field measurements. The inversion algorithm used in
this case is capable of providing an accurate recovery of depth of anomalous sources. For the
purpose of inversion, the subsurface model space was represented by a mesh of 44,198 prismatic
cells—each having a magnetic susceptibility value predicted by the inversion program. Figure G
presents a snap-shot picture of the 3D inversion results.
Figure G – 3D Inversion Model with Low Magnetic Susceptibility Anomaly
The inversion model reveals some important information. It is believed that the low magnetic
susceptibility characterizes a deep source of geothermal water, southwest of the hot springs.
Coming from the southwest, the resource is 1000-1500 ft deep near the edge of the model, and
13
Manley Hot Springs
then it quickly rises to <600 ft and in some places comes very near to the surface directly beneath
Hot Springs Slough. At the northeast terminus of the anomaly, just below Hot Springs Slough
and the runway’s northeast end, the hot water is believed to cool after it ascends from depth up to
a shallow, cold aquifer. It is theorized that as the hot water flows from depth it cools to the point
where it does not alter the magnetite mineral in the rock and soils near the surface. This would
explain why the low-magnetic-susceptibility anomaly fades out before reaching the surface.
This interpretation suggests that a deep source of geothermal water occurs entirely southwest of
the surface hot springs.
4.0 RAMPS SURVEY
4.1 General
The RaMPS methodology, although similar to traditional resistivity methodologies, utilizes a
unique data acquisition procedure to construct accurate depth sounding curves for predetermined
sounding center points, which are strategically located throughout the area of interest. These
curves help to generate a picture of subsurface structure, such as horizontal interfaces between
lithologic units. At the same time, the RaMPS acquisition procedure provides accurate lateral
profiling information for detecting vertically oriented structure such as faults. All the
information gathered from the RaMPS survey process is ultimately combined using a proprietary
plotting technique to create a subsurface 3D volume of apparent resistivities that accurately
reflect changes in the subsurface associated with contrasts in electrical properties.
The RaMPS fieldwork was not initiated until after the AeroMag survey (Phase 1 work) was
complete and modeled. Subject to areas of viable access, the RaMPS survey layout was based
partially on the findings of the AeroMag data. The RaMPS investigation consisted of five survey
lines totaling about 10,000 meters (see Figure H). The five lines, marked A through E, cover the
area around the hot springs and the northeast end of the noted magnetic susceptibility anomaly,
which terminates roughly 1000 feet south-southwest from the southernmost hot springs. Most of
the lines follow roads or trails. A total of 680 measurements were made.
14
Manley Hot Springs
Figure H – Layout of RaMPS Survey Lines
Based on the AeroMag model, the area immediately southwest of the surface expressions
appeared to be the location of greatest interest where geothermal water is suspected to flow up
from depth. The AeroMag model showed that the major anomalous feature extends even further
southwest; however, it is believed that further from the surface expressions and the deeper one
investigates, the more risk and cost involved in drilling an exploratory test well. Therefore,
taking into account the practicality and cost of drilling a test well, the RaMPS investigation
focused on an area just southwest of the surface expressions. As mentioned, this is the area
where geothermal water is believed to be flowing up from depth to near ground surface. Four of
the five RaMPS survey lines cross over this area. Two of the survey lines extend slightly
northeast of the surface expressions. These lines were surveyed to help define the subsurface
structure influencing geothermal water and its migration to the surface (see Figure H).
The RaMPS investigation was initiated on August 31, 2009. The fieldwork was completed
September 19, just before inclement weather arrived at the site (snow and freezing temperatures).
For a detailed explanation of how the RaMPS technology works, see Appendix B – White Paper
(RaMPS Technology Explained).
4.2 RaMPS Data Results and Interpretation
Data reduction, normalization and interpretation of the RaMPS data followed the fieldwork. By
itself, the Line B pseudo section (see Figure I) best shows the geothermal resource and bounding
structure. Line B crosses the Hot Springs Slough near the center, at station 1350. The major
15
Manley Hot Springs
disadvantage of Line B was that, between stations 800 and 2000, the line was curvy (being
confined to roads and trails) and it ran approximately 30° to the Hot Springs Slough, yielding
data with a degree of distortion and especially influence by the nearby slough water. The
advantage of Line B is that it clearly defines a sharp contact zone and thereby marks the most
likely location for hot geothermal water, which is adjacent to the contact zone.
Figure I – Line B Resistivity Pseudosection and Map Position
In order to analyze and present all RaMPS resistivity data, the data from all the lines were
compiled into a 3D volume so that slices could be analyzed in a similar way to the AeroMag
data. Figure J presents a slice of the data volume compiled from all the line data. The slice
position is shown by the black dotted line in Figure I.
16
Manley Hot Springs
Figure J – RaMPS Data Slice showing Apparent Resistivity Contrast
Although the color scales are slightly different, in both Figures I and J the red colors show high apparent
resistivity, such as the igneous intrusive material (or basement rock) seen in the lower left corner
of the slice. The blue colors indicate lower resistivity, which would tend to show where rocks
include water saturation, although in this figure the blue shades cover a wide range of apparent
resistivity values (from 1-50 Ohm-m, approximately). In this case interpretation relies partially
on the fact that very hot water can increase the electrical conductivity (thereby decreasing
resistivity) to a greater degree than water at normal temperatures. Some of the lowest values
(darkest blue shade) occur where it is labeled “hot water resource”, which correlates strongly
with the AeroMag anomaly. Following a small “trail” of darker blue shading to the left, it
appears that “piping” occurs toward the north-northwest direction and up to the surface, possibly
through fractures in the rock. The anomalous lows coming up to the surface coincide
approximately with the locations of some of the hot springs observed at the surface.
When analyzing these data, it is important to keep in mind that the cross-sectional views of the
3D volume include a lot of interpolated data, especially in areas that fall between or far away
from the lines shown at the surface (drawn in red). Fortunately, the area beneath the center of
the slice in Figure J represents some fairly good coverage from several lines of data; however,
much interpolation occurs in the right and far left areas. It is also important to note that
resistivity cross-sections are based on apparent resistivity values calculated from the
measurements applied to a homogeneous model of constant subsurface conductivities; therefore,
the apparent resistivities reflect smoothed or averaged values rather than true values. Moreover,
it should be noted that the depths shown in the various cross-sectional views are only estimates
17
Manley Hot Springs
based on a homogeneous model. To improve depth accuracy of the RaMPS cross-sections, test
wells would have to be drilled to calibrate the model.
When acquiring the RaMPS data, the site conditions presented a fairly conductive scenario
beginning near-surface, which tends to mask the ability to resolve deeper structure to some
degree. Also, the water in the Hot Springs Slough made it very difficult to get accurate readings
around the slough. For most of Line A which ran along the slough, it became apparent that the
electrical current did not penetrate to normal depths and the readings were often inconsistent,
probably because electric current paths were dominated by slough water. Because of this, more
than half of Line A data had to be removed from the compiled data volume to achieve an
acceptable degree of continuity in the volume before plotting the data. This left a rather large
“hole” in the dataset directly over much of the resource delineated by the AeroMag inversion
results. Fortunately, several RaMPS lines crossed over the area near the northeast terminus of
the AeroMag anomaly, allowing some information to be gleaned in this area—as shown in
Figures I and J. Slices taken further to the southwest tend to not show the anomaly as well,
mostly because of this “hole” in the data and the fact that it must be interpolated a long distance
between opposite ends of Lines B and C to fill in the data volume where the resource is believed
to be located. Given these facts, the proposed drilling locations presented in the next section rely
more heavily on the AeroMag inversion result than directly on the RaMPS dataset. Fortunately,
the AeroMag data were acquired on a tight grid (100 meters between flight lines) and is therefore
suited for the purpose.
5.0 SUMMARY OF INVESTIGATION AND RECOMMENDATIONS
5.1 Summary of Results
The analysis and interpretation of both the AeroMag and RaMPS resistivity data have provided
insightful and essential information regarding the probable source of the Manley Hot Springs
geothermal water. Both datasets strongly indicate that a deep source of geothermal water lies to
the southwest of the hot springs, and that this hot water ascends from depth up to a shallow
aquifer as it moves northeastward toward the surface expressions.
The RaMPS data delineate a sharp contact between high and low resistivity zones along the
northwest boundary of the projected geothermal resource. Accurate delineation of the resource
itself, given the RaMPS data alone, is somewhat obscured due to difficulties encountered in
achieving penetration on lines running near and along the Hot Springs Slough. In conjunction
with the AeroMag data, however, the resource can be characterized much more accurately.
Purposefully, the AeroMag data were collected on very close flight lines (100 meters apart),
which allowed for the creation of an accurate inversion model of magnetic susceptibility
contrasts that characterizes the depth of the zone of hydrothermal alteration. This depth
information provided by the inversion model is critical, especially given that no deep well logs
existed in or around the RaMPS survey area to help calibrate depths of resistivity pseudo
sections. The data and models used to provide the interpretation in this report will be made
available for TDX and their consulting geologists (Roger Bowers) as needed.
18
Manley Hot Springs
5.2 Recommendations
The information presented herein will provide a guided and cost-effective approach to drilling
and any further work in characterizing the geothermal resource at Manley Hot Springs. Figure K
shows depth slices of the AeroMag anomaly at 100, 200, and 300 meters. To intercept hot water
before it ascends from depths and cools, two recommended drilling targets—labeled A and B—
are noted in Figure K. Based on the data, priority is given to neither target, but should rather be
determined by accessibility. It is recommended the test well(s) be drilled to at least 200-300
meters to prove the resource.
Figure K – Proposed Drilling Targets A and B
There are no other recommendations made or implied as a result of this investigation.
Willowstick does not specialize in geothermal development, engineering consulting or
construction. Willowstick simply focuses its expertise on groundwater characterization by
mapping, modeling and monitoring electric current flow distribution and modeling magnetic
susceptibility through subsurface areas of interest.
19
Manley Hot Springs
The information contained herein should be compared with all known information of the site to
further characterize and substantiate subsurface conditions impacting geothermal activity
beneath the surface expressions and underlying soil / bedrock formations.
6.0 DISCLAIMER
6.1 General
The data, interpretations and recommendations obtained from the survey and modeling
methodologies are based upon sound applied physics. By definition, the evaluation of geologic,
hydro-geologic and/or geophysical conditions is a difficult and an inexact science. However,
Willowstick feels strongly that the technologies employed herein have yielded information that
will greatly help characterize the geothermal resource in question.
We certify that this geophysical investigation and report was conducted and prepared by those
listed in Appendices A & C. Willowstick makes no warranty or representation regarding the
acceptability of any findings or recommendations in this report to any governmental or
regulatory agencies whatsoever.
20
Manley Hot Springs
APPENDIX A – HELICOPTER AEROMAGNETIC SURVEY REPORT
21
Acquisition and Processing
Helicopter Aeromagnetic Survey
Manley Hot Springs, Alaska
Performed for:
TDX Power, Inc.
Performed by:
EDCON-PRJ, Inc.
July 2009
1
Table of Contents
Table of Contents ......................................................................................................................1
Table of Figures.........................................................................................................................1
Introduction:.............................................................................................................................2
Manley Hot Springs Survey Area:..........................................................................................2
Survey Equipment:...................................................................................................................5
Aircraft:.................................................................................................................................5
Airborne Geophysical Equipment:.....................................................................................5
Ground-based Geophysical Equipment:............................................................................5
Personnel and Base of Operations:.........................................................................................5
Production Summary:............................................................................................................13
GPS Data Acquisition and Processing:.................................................................................14
Data Processing .......................................................................................................................15
Flight Path Recovery:.............................................................................................................15
Magnetic Data:........................................................................................................................15
I.G.R.F.:...................................................................................................................................15
Diurnal Correction:................................................................................................................16
Leveling:...................................................................................................................................16
Micro-leveling:........................................................................................................................16
Reduction to the Pole:.............................................................................................................17
Deliverables:............................................................................................................................18
Summary:................................................................................................................................20
Table of Figures
Figure 1: Manley Hot Springs, Alaska Location Map..............................................................3
Figure 2: Planned Heli-mag Survey Program...........................................................................4
Figure 3: Survey Helicopter, Robinson R44, N544TP.............................................................6
Figure 4: Survey Helicopter Towing Magnetometer Sensor Bird Offsets ...............................7
Figure 5: Helicopter Pilot Display, Radar Altimeter and Trimble GPS Antenna.....................8
Figure 6: Radar Altimeter Display............................................................................................9
Figure 7: Magnetometer Bird with Cesium Magnetometer Sensor mounted in nose and
preamplifier in the rear..............................................................................................................10
Figure 8: Base Station Magnetometer at the Manley Airstrip................................................11
Figure 9: Base Station Magnetometer and Base GPS.............................................................12
Figure 10: Total Magnetic Intensity Map...............................................................................19
2
Acquisition and Processing
Helicopter Aeromagnetic Survey
Manley Hot Springs, Alaska
July, 2009
Introduction:
During the period July 18 to 24, 2009 a Helicopter Aeromagnetic Survey was performed by
EDCON-PRJ over Manley Hot Springs, Alaska. A Pico Envirotec AGIS-XP Helicopter-
magnetometer system with a Scintrex towed-bird cesium-vapor magnetometer was used.
Navigation and positioning were accomplished using Global Positioning System equipment
and methods. A base station magnetometer and a base station GPS were operated at the
Manley Hot Springs Airport throughout the survey. A Robinson R44 helicopter, N533TP,
was utilized as a survey aircraft and Cessna 182, N6002J, was used as a support and
mobilization aircraft.
Survey operations were completed on July 23, 2009. Processed survey data including a total
magnetic intensity map were transmitted to TDX Power’s consulting geologist Roger Bowers
on July 30, 2009.
These data were acquired and processed by EDCON-PRJ under job number 29012.
Manley Hot Springs Survey Area:
The Manley Hot Springs location is shown in the map in Figure 1, the planned program is
shown in the map in Figure 2. Northwest-southeast primary survey lines are spaced at 100
meter intervals and the northeast-southwest tie-line spaced at 500 meters. A modified drape
program was flown with a nominal helicopter terrain clearance of 500 ft AGL (above ground
level), this resulted in a nominal magnetometer sensor height above the ground of
approximately 408 ft (125 m). A total of approximately 330 line-km were planned, over 500
line-km were flown to insure good data coverage.
3
Figure 1: Manley Hot Springs, Alaska Location Map
4
Figure 2: Planned Heli-mag Survey Program
5
Survey Equipment:
The following survey equipment was used.
Aircraft:
Robinson R44 helicopter, N544TP, chartered from JayHawk Air, Anchorage, Alaska
Cessna 182, N6002J, support and mobilization/demobilization aircraft
Airborne Geophysical Equipment:
Pico Envirotec AGIS-XP Airborne Geophysical Information System s/n 0711005
Hemisphere R-100 GPS with Novatel GPS702 Antenna
Pilot navigation display unit
Magnetometer survey bird with Scintrex CS2 cesium magnetometer and preamp
Trimble 5700 Helicopter GPS with Zephyr antenna
Ground-based Geophysical Equipment:
GEM 19 Base Station Magnetometer
Trimble 5700 base station GPS with Zephyr Geodetic antenna
Personnel and Base of Operations:
These data were acquired under the direction of John Seibert, EDCON-PRJ geophysicist and
fixed-wing support aircraft pilot, The helicopter was chartered from JayHawk Air and piloted
by Mark Barker. The crew was based at the Manley Road House. Preliminary data analysis
and GPS data processing was performed in the field. Final data processing and analysis was
performed by EDCON-PRJ in Denver, Colorado.
6
Figure 3: Survey Helicopter, Robinson R44, N544TP
7
Figure 4: Survey Helicopter Towing Magnetometer Sensor Bird Offsets
8
Figure 5: Helicopter Pilot Display, Radar Altimeter and Trimble GPS Antenna
9
Figure 6: Radar Altimeter Display
10
Figure 7: Magnetometer Bird with Cesium Magnetometer Sensor mounted in nose and
preamplifier in the rear
11
Figure 8: Base Station Magnetometer at the Manley Airstrip
12
Base GPS
Base Mag
Figure 9: Base Station Magnetometer and Base GPS at Manley Airstrip
13
Production Summary:
The survey equipment arrived in Anchorage on Thursday July 16, 2009. The equipment was
checked and installed in the survey helicopter that afternoon and on Friday July 17, 2009.
The survey helicopter and support airplane departed Merrill Field in Anchorage at 10:00 on
Saturday and arrived at Manley Hot Springs at approximately 13:00 hrs that day. Several
small but frustrating problems with the survey equipment were identified and solved that
afternoon and on Sunday July 19, 2009. The bulk of the program was flown on Monday
through Wednesday July 20 – 22, 2009. The survey helicopter and support airplane departed
Manley Hot Springs on Thursday July 23 and returned to Merrill Field, Anchorage Alaska. A
Total of 24 helicopter flight hours and six fixed-wing flight hours were required to complete
the project (Merrill Field to Merrill Field).
The crew based at the Manley Hot Springs Road House during the project. Helicopter and
fixed-wing fuel was obtained from Hot Springs Aviation at Manley Hot Springs.
Survey data was evaluated for completeness and quality in the field and then transmitted via
ftp to EDCON-PRJ in Denver on a daily basis during the project.
14
GPS Data Acquisition and Processing:
Two GPS systems were operated during the survey, a Hemisphere R-100 GPS with a Novatel
GPS702 antenna and a base and helicopter-mounted Trimble 5700. The Hemisphere GPS
provided real-time, autonomous GPS positions to the helicopter navigation system. The
Trimble GPS units provided one-second dual-frequency phase data for post processing. The
location of the Trimble base was determined using OPUS, as follows:
FILE: 84851990.DAT 000082118
NGS OPUS SOLUTION REPORT
========================
REF FRAME: NAD_83(CORS96)(EPOCH:2003.0000) ITRF00 (EPOCH:2009.5453)
X: -2355824.762(m) 0.006(m) -2355825.685(m) 0.006(m)
Y: -1325377.809(m) 0.036(m) -1325376.770(m) 0.036(m)
Z: 5757761.821(m) 0.018(m) 5757762.168(m) 0.018(m)
LAT: 64 59 57.73083 0.019(m) 64 59 57.72694 0.019(m)
E LON: 209 21 42.96888 0.033(m) 209 21 42.86524 0.033(m)
W LON: 150 38 17.03112 0.033(m) 150 38 17.13476 0.033(m)
EL HGT: 90.124(m) 0.013(m) 90.564(m) 0.013(m)
ORTHO HGT: 81.263(m) 0.121(m) [NAVD88 (Computed using GEOID06)]
UTM COORDINATES STATE PLANE COORDINATES
UTM (Zone 05) SPC (5004 AK 4)
Northing (Y) [meters] 7210465.059 1225382.169
Easting (X) [meters] 611363.354 469901.683
The above Trimble Base location and height were used to process the helicopter-borne
Trimble GPS data using Waypoint Software to produce a one-second file of helicopter
location and elevation. The Trimble elevation are much more accurate than the autonomous
Hemisphere GPS data. The Trimble Orthometric height (based on Alaska Geoid 06) were
used for final magnetic data processing.
15
Data Processing
The data were processed using the following steps:
Flight Path Recovery:
The GPS vertical and horizontal coordinate outputs were recorded as latitude, longitude, x, y
and ellipsoid height using the WGS84 geographic coordinate system. Mapping parameters
for processed digital and mapped data are the following:
Projection: WGS84
Zone: 5
A speed check of the location data was completed, and the line location with the derived
aircraft speed information mapped for editing. After editing, the Trimble GPS data were
merged with the data set and accepted for the final flight path map production.
Magnetic Data:
Digital magnetic data from the airborne acquisition systems was received by FTP. The data
were read and converted to a line location file.
Data Editing
• Profile plots of the magnetic data for each line were inspected for noisy or
missing data.
• The data quality was considered good, and no filters were applied.
• No deculturing of the data was performed.
I.G.R.F.:
The International Geomagnetic Reference Field, updated to the dates of the survey, was
calculated and applied to the data set.
16
Diurnal Correction:
The base magnetometer data were inspected and compared with the observed magnetic data
trace. The observed diurnal, corrected for the I.G.R.F. values for the location of the base
station, were hi-cut filtered to remove noise and subtracted from the observed magnetic data.
Leveling:
Misties at line intersections were calculated and adjusted to minimize mistie errors. Initial
leveling adjustments were completed using a DC level adjustment to compensate for long
wavelength diurnal effects. The average intersection mistie before DC adjustment was 1.75
nT; after DC adjustment, the average mistie was 0.98 nT. After final leveling the average
mistie was 0.32 nT. Micro leveling was used to produce the final leveled data. High frequency
noise was present, and varied in frequency and amplitude by line. The source of the noise is
unknown but could have been caused by the helicopters rotor blades or a connector problem
with the magnetometer. The high frequency noise was still present on the final leveled mag.
Weiner filtering was used to isolated the noise and then removed from the Total Magnetic
Intensity.
Micro-leveling:
Even after standard leveling is applied to magnetic data (e.g., DC least squares adjustment
using misties between profile and tie lines), some corrugation is usually evident in the grid
made from the data. This corrugation is due to small mismatches between adjacent lines
arising from residual heading errors, small differences in flight elevation, and horizontal
positioning errors. The corrugation can be removed from the grid by splitting the gridded
data into matching low-pass and high-pass components, applying tuned strike suppression
filters along the profile and tie line directions to the high-pass component, and reassembling
the result with the low-pass component. This destroys short-wavelength geological
anomalies oriented along the flight and tie line directions, but these are unrecoverable
anyway in the presence of corrugation. Variations of this procedure are standard in the
industry, and are known generally as decorrugation.
The remaining problem is to transfer this correction back to the profile data. Simply
extracting the profiles from the gridded data yields a result which lacks the short-wavelength
content of the original data; the idea is to retain the shorter wavelength components in the
profile data, while using the longer wavelength components of the data extracted from the
decorrugated grid.
The procedure used is as follows. The spectrum of the difference between the profile data
and the extracted profiles is analyzed to design a low-pass filter that reflects the
long-wavelength part of the difference, and the filter is applied to the difference. The
low-pass difference is then subtracted from the profile data, which is equivalent to replacing
the long-wavelength component of the profile data with that of the profile extracted from the
grid. This is a variation of the procedure known as micro-leveling.
17
The differences between the profile data before and after micro-leveling are quite small,
generally less than 1 nT except for DC shifts. However, the final data now interpolates to a
grid which is essentially free of corrugation.
Reduction to the Pole:
Reduction to the Pole calculates the field that would be observed if the survey area were
located at the north magnetic pole. This transformation shifts the magnetic anomalies more
nearly over the causative bodies. The Reduced-to-the-Pole grid used an inclination of 76.85
degrees and a declination of 20.35 degrees.
18
Deliverables:
The following are the deliverable products of this project:
tmi.pdf: Total Magnetic Intensity map in pdf format
ttp.pdf: Reduced to Pole map in pdf format
hg.pdf: Horizontal Gradient map in pdf format
tilt.pdf: Tilt Derivative map in pdf format
tmi_geo.grd: Total Magnetic Intensity grid in Geosoft grid format
rtp_geo.grd: Reduced to Pole grid in Geosoft grid format
hg_geo.grd: Horizontal Gradient reduced to pole magnetics grid in Geosoft grid format
tilt_geo.grd: Tilt Derivative reduced to pole magnetics in Geosoft grid format
tmi.xyz: Total Magnetic Intensity grid in ASCII XYZ grid format.
rtp.xyz: Reduced to Pole grid in ASCII XYZ grid format
hg.xyz: Horizontal Gradient reduced to pole magnetics grid in ASCII XYZ grid format
tilt.xyz: Tilt Derivative reduced to pole magnetics in ASCII XYZ grid format
manley.dat: Survey line data in Geosoft XYZ format
29012_Manley_Report.pdf: This report in pdf format
Survey Line Data Format is shown below:
Columns Format Description Units
1-8 A8 Line Name Alpha
9-20 F12.5 Latitude (WGS 84) Decimal Degrees
21-32 F12.5 Longitude (WGS 84) Decimal Degrees
33-43 F11.1 UTM X Meters (zone 5)
44-54 F11.1 UTM Y Meters (zone 5)
55-63 F9.0 GPS Time Seconds of the week
64-70 F7.0 Radar Altimeter Feet
71-78 F8.0 GPS Elevation Feet
79-87 F9.2 Raw Magnetics nT
88-96 F9.2 Final Magnetics nT
97-105 F9.2 Diurnal Magnetics nT
19
Figure 10: Total Magnetic Intensity Map
20
Summary:
The survey was mobilized rapidly at the clients request. There was some delay at the start of
the project due to minor system failures which were corrected. The project area was generally
very smoky due to numerous large wildfires south of the project area, the smoke from these
fires caused some flight delays and required aborting some survey lines due to insufficient
flight visibility.
The geophysical product is of high quality and will provide a tool to further understand the
geology of the project area.
Sincerely,
EDCON-PRJ, Inc.
_____________________
John E. Seibert
_____________________
Nick Anderson
Manley Hot Springs
APPENDIX B – WHITE PAPER (RAMPS TECHNOLOGY EXPLAINED)
WWhhiittee PPaappeerr
RRaaMMPPSS TTeecchhnnoollooggyy EExxppllaaiinneedd
AAnn EExxpplloorraattoorryy SSuurrvveeyy aanndd MMooddeelliinngg MMeetthhooddoollooggyy tthhaatt
AAccccuurraatteellyy RReefflleeccttss tthhee LLooccaattiioonn ooff GGeeoollooggiicc SSttrruuccttuurree aanndd
LLiitthhoollooggyy AAssssoocciiaatteedd wwiitthh EElleeccttrriiccaall PPrrooppeerrttyy CCoonnttrraasstt
11814 S. Election Rd.
Suite 100
Draper, UT 84020
Tel: (801) 984-9850
www.willowstick.com
43
Manley Hot Springs
1. Introduction
RaMPS®, which stands for Resistivity Mono-pole Profiling and Sounding, is a unique and
proprietary geophysical survey and exploratory methodology developed by Willowstick
Technologies™ by combining traditional resistivity sounding and profiling techniques into an
integrated surveying method. It is not only unique in the way the data is acquired, but unique in
the way the information is processed, plotted, and interpreted. Although similar in many
respects to traditional resistivity surveys, the RaMPS methodology has proven to be more
accurate and insightful than traditional resistivity for resolving geologic structures and lithology
(horizontal and vertical alignment).
The RaMPS technology was first conceived many years ago by Jerry R. Montgomery, PhD,
inventor of the patented AquaTrack geophysical technology and co-founder of Willowstick
Technologies. While working as a senior geophysicist for a well known mining company, Dr.
Montgomery performed a variety of resistivity profiling and sounding surveys in many geologic
settings prior to exploratory excavation and drilling. In the process of comparing the physical
observations with electrical property measurements obtained through traditional resistivity
techniques, Dr. Montgomery observed that the resistivity pseudo-section plots (or subsurface
cross-sections based on the theory of apparent resistivity) tended to misalign the anomalies with
the corresponding structures observed in the excavation and drilling information. A further
examination of the subject proved that in general, the interpretation of resistivity by traditional
methods often yielded misleading information about the subsurface properties. The same holds
true for induced polarization or IP data, which is collected and plotted with the same survey
configurations. As a result, Dr. Montgomery began to develop a new methodology for resistivity
profiling and sounding based on observations and theory. The new methodology involves some
key changes to the survey configuration as well as the complementary data reduction, plotting,
and interpretive procedures.
Since the time the original RaMPS methodology was conceived, Willowstick Technologies’ staff
members have refined the data acquisition process as well as the processing, plotting, and
modeling techniques that are currently used. As will be explained and demonstrated in this
White Paper, the RaMPS technique has proven more accurate, insightful, and cost effective in
comparison to traditional resistivity profiling and sounding techniques for resolving subsurface
geology. The fundamental similarities and differences of the RaMPS and standard resistivity
techniques are presented in this paper along with a case study applied to a deep and geologically
complex site. However, because the survey configurations, data acquisition processes, data
reduction and modeling practices are considered proprietary, some specific details of the RaMPS
methodology are intentionally omitted.
2. General Description
The RaMPS survey method uses DC electrical current to induce current flow in the subsurface.
Measurements of potential differences are made using electrodes placed at strategic surface
locations. Subsurface resistivity is calculated using the standard and currently accepted
equations based on the physics and the array geometry (electrode positions). The equations used
44
Manley Hot Springs
with the RaMPS methodology can be reviewed in geological survey professional paper 499
“Interpretation of Resistivity Data” by Van Nostrand and Cook.
All potential measurements are made between two half-cell electrodes and are repeated over
numerous cycles of both positive and negative electric current flow. This allows for the removal
of the DC offset (spontaneous potential) simultaneously while the repeat measurements are
gathered to statistically improve the accuracy of the data.
The RaMPS method utilizes a unique data acquisition procedure to construct accurate depth
sounding curves at predetermined sounding center points, which are strategically selected along
each survey line. These center points are similar to sounding centers in a standard Schlumberger
array. Sounding curves can be interpreted using vertical sounding models to identify interfaces
such as water tables or boundaries between lithologic units having a contrast in electrical
properties. The RaMPS method also accumulates information in a unique way to measure lateral
variations along a profile line and accurately identify changes in geologic structure. The
methodology has been tested and proven in many cases to map geologic structure more
accurately than can be obtained by the traditional arrays and traditional interpretation. This is
demonstrated in the case study. All the information is ultimately combined to create a
subsurface 3D model of apparent resistivity that accurately reflects the location of geologic
structure associated with electrical contrast.
The primary difference between RaMPS and standard resistivity starts with the way the data is
collected. It is a common approach with resistivity surveys to first obtain lateral profiles for
reconnaissance or for “scouting” out an area, and then to follow up with more detailed vertical
electric soundings (VES) in desired locations to supplement the profile information. With
RaMPS, The electrodes are placed so that both the lateral profile and VES information is
gathered simultaneously which minimizes the in-field expense. This results in the acquisition of
more measurements from which models of the subsurface can be created at minimal expense.
3. Equipment
The equipment used to measure the resistivity properties of subsurface rock formations is
comprised of an accurate data logger that interfaces with a laptop computer to monitor and
record the information. The computer provides real-time resistivity calculations, plots of
sounding curves and resistivity pseudo-sections on the fly. Digital multi-meters built into the
data logger are galvanically coupled to the earth through two half-cell reference electrodes. The
data logger is accurate to .3 µV on a 25 mV scale which is comparable to available resistivity
equipment. In addition to the receiver equipment, an electric transmitter is used to generate
direct current in the earth through galvanic coupling. The transmitted electrical current is also
measured by the data logger. In general, the data logger eliminates discrepancies between
measurements and improves overall data accuracy. All measurement station positions are
determined using a Global Positioning System (GPS) with an accuracy of about one meter. This
spatial information is used to map the location of the measurement station as well as for
reduction and interpretation of the data.
45
Manley Hot Springs
4. Data Collection
Like many traditional surveys, the RaMPS data acquisition process collects resistivity,
spontaneous potential (SP), and induced polarization (IP) data at every measurement station.
Unlike traditional surveys, the array design and the movement of electrodes follows a unique
prescribed pattern that minimizes the error in locating geologic structures.
The RaMPS measurements are all taken in the time domain. The DC energizing cycle is based
on a four-second pulse rate that follows a four-step sequence. The first step in the sequence is a
four-second application of positive electric current, the second step is four-seconds of no electric
current, the third step is four-seconds of negative electric current, and the fourth step is four-
seconds of no electric current. This four-step sequence is repeated as many times as necessary to
obtain a statistically significant low deviation of measured and recorded values. At each change
in the energizing sequence (positive electric current flow, negative electric current flow, or no
electric current flow) the charging or discharging rate is measured. The rate of discharge from
the earth, measured in millivolts per volt, is used to determine the IP effect. The potential
difference and electric current flow measured during the “ON” cycles is used to calculate the
apparent resistivity in Ohm-meters at each station. During the “OFF” cycles, the potential
difference between the half-cell reference electrodes is measured in millivolts to record the SP
effect, which can supplement the resistivity data by providing information on the natural ion
movements in the subsurface. Resistivity, IP, and SP values are all reported in standard units.
The spacing between measurement stations is adjusted according to the level of detailed
necessary to meet survey objectives. Station spacing may also be influenced by the particular
site conditions and adjusted based on the electrical properties associated with the particular
geologic setting, which can vary drastically. The distance between the source and receiver
electrodes determines the approximate depth of investigation. For each transmitter electrode
dipole location, the potential measurements are taken at increasingly longer distances from the
source dipole until the desired depth of investigation is obtained or until the potential difference
drops below a readable level.
The potential difference readings, along with the measured transmitter electric current flow and
the known GPS station coordinates, are all used together to calculate the apparent resistivity of
the subsurface rocks through which the current is flowing. Based on a model of homogeneous
electrical conductivity background, this calculation is made automatically by Willowstick’s
resistivity recording and plotting software so that a cross-section of the subsurface can be
visualized as the readings are being taken. This facilitates on-the-spot decisions to be made
regarding data collection and station spacing in order to maximize productivity and acquire data
at the necessary level of detail. The measured data and resistivity calculations are also stored in
the computer’s spreadsheet to allow for a closer examination of the data.
5. Explanation of Measurements
The three measurements obtained by the RAMPS technology include: (1) resistivity; (2) induced
polarization or IP; and (3) spontaneous potential or SP. All of these provide different
information about subsurface conditions. In most cases, the resistivity information is the most
46
Manley Hot Springs
critical to establishing an accurate interpretation of the subsurface. The SP and IP readings
provide supplemental information to the resistivity data that can aid in the final interpretation.
The SP data, which is referenced to a single station along each profile, provides information on
electrochemical potentials and possible groundwater movement. These two effects cannot be
distinguished using SP alone. However, if the SP data is correlated with other information such
as resistivity, IP or magnetics, a better model of the site can be formulated because one set of
data can act as boundary conditions when modeling other conjunctive data.
IP describes the rate at which the subsurface discharges electricity. This discharge rate can be
linked to certain materials that will either slow or speed up the rate of discharge; for example,
good conductors such as water with ions or massive sulfides will discharge quickly and have a
low induced polarization; whereas, clays, disseminated sulfides, and copper porphyry deposits
have a higher induced polarization because they discharge at a slower rate. Distinguishing
between regions of high and low induced polarization may indicate changes in rock type or clay
content in unconsolidated sediments. By correlating induced polarization and resistivity
anomalies, models of the subsurface resistivity and IP can be formulated to express either a
comprehensive or targeted interpretation of subsurface geology.
Resistivity measurements in general are very sensitive to groundwater, rock type, and subsurface
structure. Groundwater is very important in resistivity because it strongly influences the
electrical conductivity of the rocks through which it permeates. Rock type is also important
because variations in porosity and permeability—which control the amount of void space or
water-saturated space within rocks—can strongly affect the resistivity property of a rock. The
last effect is structure which is generally confined to more isolated parts of the data rather than
the data as a whole. Faults and other structure can be detected due to the contrast in electrical
properties between adjacent rock units and/or due to groundwater pooling within open spaces
along fractures.
6. Data Interpretation
The interpretation of RaMPS data is similar to interpreting any other traditional resistivity/IP
survey. Resistivity and IP pseudo-sections are created to show the variation in resistivity along a
survey line and serve as one method to graphically present the interpretation. The true depth at
which the electric current penetrates into the subsurface depends on a number of factors
including the geology and the electrical properties of the subsurface rock under investigation. To
reflect accurate depth information, models of individual sounding curves can be prepared and
calibrated to existing well logs. Pseudo-sections of the calibrated data are used to identify
anomalies and to discriminate between lateral changes and those related to depth. Once these
anomalies are identified and understood in the pseudo-sections, the data is combined to generate
subsurface volume and/or cross-section plots which show the 3D structure of the subsurface with
interpretive information about the subsurface geology.
47
Manley Hot Springs
7. Case Study – Cove Fort Geothermal Site, Sulphurdale, Utah
A. General Information
Willowstick Technologies performed a Resistivity Mono-pole Profiling and Sounding (RaMPS)
geophysical survey of the Cove Fort Geothermal Resource near Cove Fort / Sulphurdale, Utah.
The purpose for the RaMPS geophysical investigation was to better characterize the geothermal
resource as well as to identify a suitable location for an injection well field required of the
proposed geothermal power plant. The location and successful operation of the injection well
field is of utmost importance for the permitting, development and operation of the proposed
Cove Fort Power Plant. From previous investigations completed on the Cove Fort geothermal
resource (which were performed by Willowstick and others) it appeared that the area containing
the greatest amount of geothermal fluid was located along a fairly narrow northeast/southwest
striking feature containing geothermal fluid concentrations about 2,000 to 3000 feet below
ground surface.
In order to better characterize the geothermal resource as well as to efficiently and cost
effectively identify a suitable injection well field site, Willowstick Technologies proposed a new
resistivity sounding / profiling technique to characterize deep subsurface structure likely
influencing the geothermal resource in the area. This exploratory survey technique (RaMPS)
was applied at the Cove Fort site to obtain and compare subsurface information over the main
resource (where a significant amount of information and well log data exists) with RaMPS data
obtained west of the resource. This was done in an effort to calibrate the geophysical data with
existing well log information and to create an accurate subsurface model of the resource west
and down gradient from the known production zone. The survey was targeted to identify
structure and faulting changes influencing the hydro-geology of the site. Identifying these faults
in the subsurface (depth, strike, and dip) is of significant importance in characterizing the
geothermal resource as well as determining a suitable injection well field location.
B. Survey Layout
The fieldwork consisted of four lines totaling about 40,000 feet. The four survey lines
surrounded and crossed over the known geothermal resource (see Figure 1 below). Fifteen
sounding centers were identified on the four survey lines. Measurements were taken along each
line using each of the base points in one or both directions, resulting in a total of 21 different
profiles and 290 measurements. The data reduction, normalization and interpretation developed
2D maps, graphs and figures as well as a 3D model of the resource. Figure 1 below shows a plan
view of the site and identifies the locations of the RaMPS survey lines and the 15 sounding
centers along the lines. The four survey lines, labeled A, A', B and C, surround and cross over
the known geothermal resource.
48
Manley Hot Springs
Figure 1 – RaMPS Survey Layout
C. Results of Investigation
The RaMPS resistivity profiling and sounding survey measurements were used to generate a 3D
model. The visualization tools for this model run in the MATLAB™ modeling and
programming environment. Figure 2 below represents a snapshot view of a vertical slice or
profile view through the 3D model.
The geophysical data incorporated into the model shows significant changes and trends in the
subsurface that match very closely with well log data and other studies performed on the site.
Using the RaMPS subsurface exploratory survey technique to investigate the geothermal
resource a suitable injection well field was identified and recommended for development.
49
Manley Hot Springs
Figure 2 – Cross Section of 3D Model
Figure 2 above represents a summary of the findings of RaMPS geophysical investigation. This
is a snapshot of a vertical slice through the 3D model created using the RaMPS data. This east-
west cross-section is centered just north of the geothermal resource’s center. This particular
view looks north through the area of investigation. There are 3 existing wells and other surface
features used to orient the reader’s position with respect to the site and subsurface resource. The
dark blue shading in the figure represents low resistivity zones. The orange shaded areas
represent high resistivity zones. Wells 24-7, 34-7B and 42-7 are just a sampling of
approximately 20 wells drilled into the resource at this site. Because of scale and the many wells
on the site, only 3 wells are shown in this particular profile view of the model. These wells and
others on site confirm and support the accuracy and findings of this RaMPS investigation. For
example, Well 24-7 was completed to a depth of 1,391 feet. This well was never fully developed
because of its marginal production according to well log records. The RaMPS survey confirms
that this well resides on the edge of the resource which accounts for its marginal production.
Well 34-7B was completed to 1,148 feet. This well is reported to be a good well; however, it
was only completed to the upper reaches of the resource near the interface of the hot water and
steam cap. Well 42-7, which was originally drilled to 7,000 feet (bgs) was plugged at 3,100 feet
(as shown in the figure). It was perforated near the 2,500 foot depth where spent geothermal
50
Manley Hot Springs
fluid was historically injected from the original power plant. Injection well 42-7 was used to
discard spent geothermal fluid near the bottom of the hot water production zone.
Figure 3, which is a reproduction of Figure 2, shows added marks and notations to highlight
anomalies observed in the data and show a theorized interpretation of the overall geothermal
resource.
Figure 3- Interpretation of Cross Section
The RaMPS model indicated that the geothermal resource lies in a horst & graben setting. A
major fault exists where the geothermal fluids are most concentrated. This major fault separates
the eastern graben from the horst. It is theorized that as groundwater flows from the mountains
located east of the site, it is conveyed downward into a major fault zone where the water is
trapped and super heated from below. Heat probably flows upward along the fault zone from
deep within the earth. The heated groundwater is trapped in the graben which spills over the
horst and flows westward or down-gradient into the valley. The groundwater cools as it flows
westward. This spilling of geothermal fluid over the horst at this location is referred to as a tea
cup effect and is noted as such on the drawings (see Figure 3).
51
Manley Hot Springs
The major fault zone referred to above is believed to be a weakened area where ancient volcanic
material has pushed upward toward the surface of the ground. A surface expression of this
ancient volcano can be observed in the topography of the site and is located northwest of the
main geothermal resource. The presence of the ancient volcano is supported in the geophysical
ground magnetic data (see Figure 4) and RaMPS resistivity volume (Figure 3).
Figure 4 – Magnetic Contour Map
The RaMPS data identified an alteration interface that reflects changes in resistivity due to past
alteration of rocks by geothermal fluids. This interface between altered and non-altered rocks
comes very close to the surface over the known geothermal resource area. Figures 2 and 3 show
the interface as a net draped beneath the surface. Figure 5, which utilizes a USGS topographic
overlay, was created to more easily visualize this interface. The dark blue shading in Figure 5
shows where the altered material is very near the surface and the sulfur pit at the south end of the
resource. The blue area is clear evidence of the geothermal fluid activity which reached the
surface.
52
Manley Hot Springs
Figure 5 – 3D View of Alteration Interface
Figure 6 below shows the location and orientation of faults observed in the geophysical profiling
work. This map was created from the resistivity profiling data. Faults are numbered #1 through
#12 in the figure. It should be noted that Faults #3 and #4 represent the major faults involved in
trapping and concentrating the geothermal fluids and where groundwater is heated from beneath.
Faults #1 and #2 have a south-southwest strike and a westward dip. They represent the eastern
edges of the graben lying just east of the main horst structure in the center (see cross section in
Figure 3). Fault #4 dips slightly eastward and represents the western edge of this graben. Fault
#7 is likely the major range front fault with other small faults paralleling it (Faults #5, #6, #8 and
#9). These range front faults also have a south-southwest strike and they dip to the west. The
horst structure that traps the geothermal water is located between Fault #4 and the range front
faults.
53
Manley Hot Springs
Figure 6 – Fault Location Map
The combination of profiling with sounding measurements has made possible the creation of a
3D model from which Figures 2 and 3 were created. It should be noted that as geothermal water
spills over the horst (as shown in Figure 3) the geothermal fluids flow westward and downward
towards the range front fault. The escaping geothermal fluid is first intercepted by Faults #5 and
#6. The area bounded between Faults #5 & #7 is the area recommended for the injection well
field. This location meets the criteria for an ideal injection well field based on the following
observations: (1) this area is hydraulically connected to the geothermal resource but down
gradient of the resource; (2) it is located thermally down gradient from the main resource, where
cooler temperature groundwater resides; (3) this area appears to be a highly porous zone capable
of receiving the spent geothermal fluid; (4) this site is located down-gradient (topographically)
from the power plant, which will minimize pumping costs. It is also in relative close proximity
to the proposed power plant; and (5) this area also resides within the BLM leased land for the
geothermal resource.
The proposed operation of the power plant will require geothermal fluid to be pumped up out of
the production zone (located east of the horst) and the spent geothermal fluid injected back into
the ground west of the horst. Injection of the spent geothermal fluid would be driven by gravity
54
Manley Hot Springs
as this injection well field is located down-gradient (topographically) from the power plant. In
utilizing the geothermal resource in this manner, the power plant will have no negative impact to
the geothermal resource. Rather than the water naturally spilling over the horst (tea cup effect)
the proposed operation of the power plant would simply intervene by acting as the tea cup.
D. Conclusions
The RaMPS survey methodology provided useful and essential information for locating
electrically conductive zones related to faulting and/or structure changes which allowed for the
identification and confirmation of concentrated geothermal fluid beneath the study area and
where spent geothermal water can be injected back into the ground to optimize power plant
operations without negatively impacting the subsurface groundwater regime.
A 3D model was created of the subsurface resource and surrounding area for presentation of the
data and further analysis of the geothermal resource. An interactive model cannot be
incorporated into this report; however, snapshot and cross-section views of the subsurface
resource are included. If there is interest in viewing the interactive model, please feel free to
contact Willowstick.
Willowstick Technologies does not specialize in geothermal power production but focuses its
expertise on groundwater and subsurface structural characterization, modeling and mapping.
55
Manley Hot Springs
APPENDIX C – PROFESSIONAL BIOGRAPHIES
VAL O. KOFOED, P.E.
President / Principal Engineer
Education
¾ B.S. – Civil Engineering (1983)
Brigham Young University, Provo, UT
Professional Experience – 26 Years
¾ Willowstick Technologies, LLC 2004 – present
President and Consulting Engineer. Responsible for daily operations of all groundwater
characterization investigations.
¾ Sunrise Engineering, Inc. 1983 – 2004
20 years experience as a Consulting Engineer. Principal Engineer from 1987 to 2004.
Responsible for Hydrogeology Division and water resource engineering related projects.
¾ Western Utility Contractors 1982 – 1983
11/2 years experience as Project Engineer. Estimator and Project Engineer on water resource
construction projects.
Registration
¾ Registered Professional Civil Engineer
Utah (#172947)
Arizona (#20923)
JERRY R MONTGOMERY, PH.D
Chief Geophysicist / Inventor, AquaTrack Methodology
Education
¾ B.S. – Physics (1965)
Weber State University, Ogden, UT
¾ Ph.D. – Geophysics (1973)
University of Utah, Salt Lake City, UT
¾ Post Doctoral Studies – Geostatistics (1974)
University of Leeds, Leeds, England
Professional Experience – 40 Years
¾ Willowstick Technologies, LLC 2004 – present
Chief Geophysicist. Assisted in spinning off the AquaTrack technology and Hydrogeology
Division from Sunrise Engineering into it own business unit (Willowstick). Responsible for
interpretation and further improvement of the AquaTrack hardware and software including
other new groundwater mapping technologies.
¾ Sunrise Engineering, Inc. 2001 – 2004
Research and Development Director. Responsible for improving the AquaTrack technology,
taking it from an analog to a digital technology.
56
Manley Hot Springs
¾ Self-employed 1996 – 2001
Inventor and patent of the AquaTrack technology. Conducted contracted AquaTrack
surveys.
¾ Bureau of Mines 1990 – 1996
Staff Scientist and Researcher. Involved in bio research for removal of heavy metals.
Developed electromagnetic tracking and monitoring equipment for monitoring groundwater
plumes, biological process, and in-situ leaching.
¾ U.S. Army, Dugway Proving Grounds 1986 – 1990
Operations Research Analyst. Served as Contracting Officers Representative for diverse
contracts. Devised unique technique for analyzing time dependent data and helped
developed NBC projection for M1 tank, Apachy, LCAC’s and C117’s.
¾ ASARCO, Inc. 1968 – 1986
Chief Geophysicist. Responsible for organization, direction and interpretation of geophysical
surveys. Developed programs to study minerals, groundwater and environmental problems.
Developed new geophysical technologies and expanded theories to implement and improve
geophysical interpretation.
RONDO N. JEFFERY, PH.D
Physicist / Research and Development
Education
¾ Ph.D. –Physics (1970)
University Illinois – Urbana/Champaign
¾ M.S. – Physics (1965)
Brigham Young University, Provo, UT
¾ B.S. – Physics (1963)
Brigham Young University, Provo, UT
Professional Experience – 30 Years
¾ Willowstick Technologies, LLC 2004 – present
Physicist. Assists Dr. Montgomery with all aspects of research and development.
Responsible for the electronic design and construction of the AquaTrack receiver.
¾ Weber State University 1980 – present
Professor of higher education and research. Taught courses in electronics, solid-state
physics, engineering physics, nuclear physics lab, and astronomy. Participated in numerous
research and development projects. Authored many publications and presentations.
MICHAEL L. JESSOP
Geophysicist
Education
¾ M.S. – Geophysics (2005)
University of Utah, Salt Lake City, UT
¾ B.S. – Geophysical Engineering (2002)
Montana Tech, University of Montana, Butte, MT
57
Manley Hot Springs
Professional Experience – 7 Years
¾ Willowstick Technologies, LLC 2005 – present
Staff Geophysicist. Responsible for data analysis & modeling using MATLABTM
programming package to understand probable groundwater flowpaths observed in the
AquaTrack data. Assists with data interpretation and quality control.
¾ Gradient Geophysics, LLC 2002 – 2003
Geophysics Field Crew. Worked with and directed crews on geophysical field surveys
including resistivity, IP, and magnetic data acquisition.
MICHAEL WALLACE
Geophysicist
Education
¾ M.S. – Geophysical Engineering (2006)
Montana Tech, Butte, MT
¾ B.S. – Physics (2003)
Hampden-Sydney College, Hampden-Sydney, VA
Professional Experience – 4 Years
¾ Willowstick Technologies, LLC April 2006 – present
Staff Geophysicist. Responsible for initial data interpretation and data quality control.
Also responsible for Reduction program and Field program. Assists in modeling using
MATLAB program and with data interpretation.
¾ Curtin University Exploration Geophysics Department, Perth WA 2004
Exchange Student. Assisted with land seismic, seismo-electrics, and Time Domain EM
surveys over gas reservoir. Built portable audio magnetotelluric survey system.
¾ Sweet Briar College 2003
Student Research Intern. Processed radio astronomical data in search of circular
polarization in active galactic nuclei.
¾ Hampden Sydney College 1999 – 2003
Student Research Assistant. Tested amplifier circuits for X-Ray fluorescence
spectrometer, cleaned and tested cryostat and vacuum system. Developed scripts in
Python and AWK to automate astronomical observations in small radio telescope
¾ National Radio Astronomy Observatory 2001
Engineering Intern. Worked with Metrology Group on active projects and developed low
level control software for HP Laser Measurement System.
58