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Unalaska Geothermal Exploration Final Report 1984
ORTYEN ALS THE UNALASKA GEOTHERMAL EXPLORATION PROJECT EXECUTIVE FINAL REPORT Prepared By: Republic Geothermal,Inc. For: The Alaska Power Authority December 1984 THE UNALASKA GEOTHERMAL EXPLORATION PROJECT EXECUTIVE REPORT TABLE OF CONTENTS INTRODUCTION.2...cece cece ccc cece ccc cece ene n cnc ncenceees SUMMARY .....ecw cccccccccccccces See eeseseseessesseeueseeens PROJECT ACTIVITIES AND RESULTS......ccc eee cee cece cece eee A.Exploration Surveys.....ccc ccc cece ccc ccc ccccncecncccs 1.Geologic Field Mapping..........ccc ccc ecw cc ecco eee2.Investigation of Thermal Manifestation Areas...... 3.Geochemical Survey.......ccccccccccccccccccccccece 4.Mercury Soil Survey......ccccccrccccccccccccccccce 5.Self-Potential Survey..................ecaccccccas B.Drilling Activities,Resource Discovery............... 1.Temperature Gradient Hole Drilling to 1,500 Ft.... 2.Exploratory Well]Drilling.........ccc cece ence eens C.Resource Testing...c.ccccccccccccccccccccccscccccccces .Test Facilities and Instrumentation............... Flow Test Measurements...2...ccc ccc ween cece cw ccees Reservoir Fluid Composition.........ccc ccc ccc wees Interpretation of ST-1 Test Results...............PON-eeoeD.Reservoir Delinedtion.......ccccecececcccccrcccccee eaee1.Drilling of Temperature Gradient Hole "A-1"....... 2.Electrical Resistivity Survey........ccccccncccees -.The Makushin Valley Geothermal Reservoir Model........ CONCLUSIONS FOR COMMERCIALIZATION A.Estimated Electrical Generating Potential 1.Well Production Potential.....ccc ccccccccccccecces 2.Well Power Potential......ccscccccccccccccsesccees 3.Reserve Estimation.....cc ccwcccsccccenssvcvssscces B.Resource Commercialization -Power Conversion Processes......ccccccccsccccccces Load Forecasts......cccccccccsccccccccsccccccccees Unit Sizing and Scheduling...........ccc ccccccceeGeothermalPowerDevelopmentCostComparisons..... Power Conversion Process Recommendation........... Binary System Development Costs...............208- CONCTUSTONS ...ccc ccc ccc ccc w cece cece nceceesesececsWOON&WMe°°°.°cd a9""?RNaweyweMY -. le gene,ew TT ----.ee aso ote =. "AMyee fies veshes ailenspewe> MAKUSHIN WELL ST-1 1984 FLOW TEST THE UNALASKA GEOTHERMAL EXPLORATION PROJECT 1.INTRODUCTION Geothermal Energy,in the form of naturally occurring underground steam and hot water,1s now being used throughout much of the world to commercially produce electricity.Significant development of this viable alternative energy source is now taking place not only in the western United States but also in Japan,The Philippines,Italy,New Zealand,Mexico,and in eight other countries.Worldwide,the total installed electrical generating capacity that is "fueled”solely by geothermal energy is expanding at a 16% annual growth rate,having reached a level of 3,770 megawatts in June 1984. For comparison,the total amount of electricity now being produced in the State of Alaska is equivalent to about 690 megawatts of plant capacity. The Aleutian Archipelago,with its 46 active volcanoes,has for some time been recognized to have the same essential geologic characteristics that exist in those regions which are now producing geothermal power.One of these Aleutian volcanoes is Makushin Volcano,located on Unalaska Island at a distance of only 12 miles from the two cities of Dutch Harbor and Unalaska (Figure 1).Makushin Volcano is flanked by hot springs and fumaroles (steam seeps),and it clearly represents a potential natural energy source that could be tapped and uttlized by the Unalaska Island residents. Because the State of Alaska is attempting to utilize indigenous energy sources co-located with population centers,a decision was made in 1980 to fund a geothermal exploration project on Unalaska to determine the feasibility of cost-effectively generating electricity from this potential resource.In 1981,approximately $5,000,000 was appropriated for this purpose and the Alaska Power Authority (APA)was given project responsi- bility.In 1982,Republic Geothermal,Inc.(Republic),was awarded APA Contract CC-08-2334 to conduct the geothermal exploration on Unalaska Island, together with its Alaska partner,Dames &Moore of Anchorage. From February 1982 through December 1984,the Unalaska Geothermal Exploration Project has advanced through three main phases.A final report of the Phase I project activities,which included data review,exploration surveys,and the drilling of three temperature gradient holes,was delivered to the APA in April 1983. Because encouraging results were obtained from the 1982 Phase I operations, Phase II activities were planned and undertaken during the summer field season of 1983.That work resulted in the successful discovery of a significant geothermal reservoir.Details of these results are contained in the Phase II report delivered to the APA in March 1984.During this same time,a companion study and report titled,"The Unalaska Geothermal Exploration Project,Electrical Power Generation Analysis,"was completed by Republic Geothermal. Phase III project activities were subsequently designed to obtain during thesummerof1984substantiallymoretechnicaldataonthisreservoir's temperature and pressure,its apparent longevity for sustained production, and its apparent lateral extent (size).A summary of all the results of Unalaska Geothermal Exploration Project is provided within this Executive Report,including those results most recently obtained during the final Phase III activities. The report that follows 1s a compilation of numerous documents prepared by employees of Republic,Dames &Moore,and their several subcontractors. Considerable input has also been received from Alaska Division of Geologic and Geophysical Surveys (DGGS)employees,from University of Alaska staff, and from U.S.Geological Survey (USGS)scientists.Republic Geothermal acknowledges these contributions and wishes to express its appreciation for the cooperation and spirit of communication that has greatly facilitated the accomplishment of this project's objectives. POINT KADIN.. ALASKA 166°55' 54°00' Vv MAKUSHIN VOLCANO ar MAKUSHIN BAY SCALE e u 2 3 waneseeeexLOMETERSe.r.2 3 6 8 | Qat UNALASKA Geologic Map and Geothermal Manifestations GEOTHERMAL MANIFESTATIONS (@ Fumarotic Area [@)Hot Spring Group Warm Ground GEOLOGIC UNITS Gal Quaternary Alluvium &Glacier Deposits Makushin Volcanics ital Tertiary Plutonics Unataska Formation FIGURE:1 acl close 2.SUMMARY Project activities began with field work conducted during the summer of 1982 in the Makushin Volcano area of Unalaska Island.These investigations resulted in the identification of 23 thermal manifestation areas of which only 12 were previously known.Concurrently,a series of exploration surveys were conducted,including the drilling of three 1500 feet deep holes in order to determine the most promising area for the drilling of a deeper exploration well. Well ST-1 was drilled to 1949 feet during the following summer,successfully discovering a 325°F (163°C)shallow steam zone overlying a liquid-dominated geothermal reservoir with a temperature of 380°F (193°C).Preliminary tests indicated that the reservoir ts potentially commercial. Results from a long term,34 day Flow test of well ST-1]during the 1984 Field season confirmed these results.Sustained flow of 63,000 lb/hr was achieved through a three-inch diameter wellbore with less than two psi of pressure drawdown from the initial reservoir pressure of 494 psi.This indicates a very large permeability-thickness value for the reservoir.The well productivity index obtained during this test was approximately 30,000 lb/hr/pst. Wellbore flow modeling indicates that 13-3/8 to 16 inch diameter commercial-size wells should be capable of flowing steam and hot water at rates of between one and two million Ib/hr.A single production well can be expected to produce about 9 megawatts of electrical power.Reservoir size calculations indicate that the reserve found is sufficient to meet the electricity needs of the island for several hundred years. Commercialization of this geothermal resource can be best undertaken by installing modular units of a binary cycle power plant.The total field and power plant development costs of such a project are estimated to be approximately $57,124,000 for a 6.7 net megawatt installation.This wil] result in a supply of electricity sufficient to meet the Island's current average power demand indefinitely. 3.PROJECT ACTIVITIES AND RESULTS A.EXPLORATION SURVEYS Prior to the start of thts project several reconnaissance geologic surveys had been conducted on Unalaska Island.In 1919,Madden of the U.S. Geological Survey reported that sulfur deposits and fumaroles of superheated (310°F)steam are found in the summit crater of Makushin Volcano.In 1961, Drewes (and others)of the USGS published a geologic map of the tsland,which included the locations of two additional fumarole fields found on the vol- cano's southern flank. More recently,and in substantially more detail,Reeder and Motyka (both of the Alaska Department of Natural Resources,Division of Geological and Geo- physical Surveys)described in 1981 eight fumarole fields and their accompanying hot springs located in the Makushin Volcano region.These investigations led to their preliminary conclusion that a large, high-temperature,vapor-dominated geothermal resource exists somewhere beneath Makushin Volcano. To actually confirm,delineate,and accurately characterize this suspected Unalaska geothermal resource,Republic designed an exploration program specifically appropriate for the Makushin area,taking into consideration the limited available geological data,the rugged terrain,the severe logistics, and the short Field season.The final program selected consisted of 1) geologic field mapping,2)a detailed investigation of all thermal manifestation areas,3)a geochemical survey,4)a mercury soil survey,and 5)a self-potential survey. }.Geologic Field Mapping From April 26,1982 through September 8,1982,the geology of the Makushin Volcano geothermal area was studied in the field by Republic geologists. Work accomplished during the first field season included remapping and sampling of the major lithologic units,an examination of the surface traces of fractures and faults,and,most significantly,the locating of all geothermal manifestations in the area for purposes of more thorough investigation. The results of the geologic mapping studies indicate the area is underlain by the early Miocene Unalaska Formation that consists predominantly of interbedded volcanic rocks and volcaniclastic rocks.Plutonic rocks of a gabbroic composition intrude this unit.The overlying Pleistocene to Recent volcanics consist of andesitic lavas,pyroclastics,and cinders,with the most recent volcanics being of post-glacial age.The recent volcanism on Unalaska Island is the surface expression of an underlying magma source, which is available as a heat source for a Makushin geothermal resource. 2.Investigation of Thermal Manifestation Areas The geothermal manifestations that occur at the surface in the Makushin Volcano region consist of fumaroles,hot springs,warm ground,mud pots,mud volcanoes,and hydrothermal alteration zones.Temperatures of the manifestations range from 310°F (154°C)to slightly above ambient air temperature.Of the 23 manifestation areas currently identified in the region (Figure 1),12 were known before this investigation and 11 were discovered during the 1982 field work. 3.Geochemical Survey Geochemical field work was conducted by Republic during the summer of 1982 itn cooperation with the Alaska DGSS.Several thermal and nonthermal waters were sampled and analyzed,and numerous samples of fumarole gases were collected and analyzed. The chemical analyses of Makushin thermal waters indicates two water types exist.The predominant type is a chloride-poor (<10 mg/1),near-neutral to acidic water that contains significant amounts of sulfate and carbonate with varying concentrations of calcium,sodium,and magnestum.The second type is a chloride-rich,nearly neutral water that is enriched in magnesium, potassium,and boron. The chloride-poor thermal waters,which are classified as acid sulfate, obtain their thermal energy from steam and conductive heat flow.The low chloride values indicate that they originate from rising steam accompanied by hot gases,and that a reservoir water is lacking.The steam has migrated from a steam cap that also supplied the fumaroles. The chloride-rich thermal waters occurring in both Glacier Valley and Driftwood Bay valley suggest that a liquid-dominated geothermal resource exists beneath the steam cap.The magnesium concentrations,stable isotope values,and surface temperature suggest the reservoir water has mixed with large amounts of groundwaters to form these hot springs.Stable isotopes of Makushin waters plot near the meteoric water line,except for the high temperature steam condensate samples.The chloride-rich water has a slight8180shiftthatconfirmsthemixingofgroundwaterswiththereservoir water. 4.Mercury Soil Survey Minor amounts of mercury (Hg)are typically contained in volcanic and plutonic rocks.The mercury is easily vaporized at moderate temperatures, migrating toward the surface where it is absorbed on clay minerals in the soil.Consequently,areas of near-surface thermal activity are usually overlain by soil with anomalously high mercury concentrations. Makushin Volcano 166°55' 54°00' SU NO 53°45' MAKUSHIN BAY LOAF Favs 081 AKUSHIN VALLEY IFS -UNALASKA Mercury Soil Survey Results -ppb Mercury In SoilC)108-252 ppb >252 ppb FIGURE:2 act close The mercury soi]survey conducted by Republic on Unalaska Island covered a 175 square mile area centered on Makushin Volcano.A total of 230 soil samples were collected and analyzed to determine the mercury concentrations. The concentration range is between 8 and 31,450 ppb Hg,with an average (mean)value of 454 ppb Hg.Contours of the data in Figure 2 are drawn at three times background (108 ppb),and at seven times background (252 ppb). The 108 ppb contour outlines six separate mercury anomalies in the Makushin Volcano region,with each anomaly exceeding 252 ppb Hg. The largest of the six mercury anomalies is situated on the top and flanks of Makushin Volcano and covers approximately 20 square miles.The five other mercury anomalies present in the Makushin Volcano region are of substantially smaller size and are of relatively minor significance.The mercury soil survey results suggest that much of the eastern half of Makushin Volcano is an excellent geothermal drilling target. 5.Self-Potential Survey Consideration of the applicability of many different geophysical techniques to the exploration of the Makushin Volcano geothermal area lead Republic to chose the Self-Potential (S-P)method as being most cost effective. The S-P survey covered approximately 48 line-miles on the flanks of Makushin Volcano.Field data was collected along traverse lines,with a normal station spacing on the lines of 200 yards.The survey results outlined two significant anomalies:a 600 mV negative anomaly centered northeast of Sugarloaf Cone;and a 500 mV negative anomaly occurring near Fox Canyon about 3 km southwest of Sugarloaf Cone. Computer modeling indicates that the most probable source of the two large S-P anomalies appears to be geothermal activity,with the flow of heat and/or fluid in the source regions generating the anomalies.Modeling of the maximum depth to the top of the geothermal source region is approximately 0.4 to 0.5 km (1300 to 1650 ft.)for the southwestern anomaly. In addition,a careful examination of the data reveals that a minor low S-P trough extends from upper Glacier Valley to Fumarole #1.This trough may lack greater amplitude because of the presence of the Makushin plutonic stock,so the lack of a major S-P signature over the major Fumarole Fields #1,#2 and #3 does not indicate the absence of a geothermal system in this area. B.DRILLING ACTIVITIES,RESOURCE DISCOVERY Analysis of all the acquired geological,geophysical,and geochemical] exploration survey data resulted in the initial selection of several target areas judged promising for drilling. 1.Temperature Gradient Hole Drilling to 1,500 ft. In May 1982 drill rig equipment and related supplies were barged from Anchorage to Dutch Harbor,partly disassembled,and then airlifted in 1,400 lb.weight-limited loads up to the Makushin project site by helicopter. Temporary camp facilities had concurrently been erected,and 24-hour full-scate drilling operations were begun in early June. Three temperature gradient holes (TGH)were drilled that first summer using a Longyear 38 continuous wireline coring rig.TGH "D-1"was drilled in the Fox Canyon area about one mile northwest of the base camp,near the center of superimposed mercury soil and S-P anomalies.The gabbro intrusive was reached after drilling through 1,222 feet of fresh volcanics,and core drilling was continued several hundred feet into highly altered and fractured gabbro,down to a total depth of 1,425 feet.Temperature measurements made tn TGH "D-1"after equilibration indicate that there is almost no temperature increase from the surface down to a depth of 900 feet (see Figure 3).Below that,temperatures increase at a high rate of 25 to 30°F per 100 feet, reaching a maximum of 212°F (100°C)at bottom.The results indicate that higher temperatures exist at depth,and that a relatively shallow (but deeper)hydrothermal system exists. TGH "E-1"was then drilled,near the base camp,on the NE-SW geologic fracture trend that is suggested by our lineament studies and the surface locations of Fumarole Fields #1,#2,#3 and #8.The gabbro was found,as anticipated,less than 100 feet below the surface,and E-17 was drilled to a total depth of 1,501 feet,still in the gabbroic pluton.The temperature profile in TGH E-1 was initially determined to be essentially conductive from the surface to total depth.Gradients in the first 1,000 feet were quite consistent and high,averaging 26°F/100 feet.At 1,000 feet,the gradient gradually decreases to 5°F/100 feet in the last 100 feet.The high temperature of 383°F (195°C)at 1,485 feet in TGH E-1 is well within the temperature range for commercial electrical power generation. TGH "I-1"was the third and last drilled in 1982,at a location in upper Glacier Valley three miles southwest of the base camp.This drill site was selected to determine if the superheated (306°F)steam escaping at Fumarole #3,located 4,000 feet away (upslope),was coming from a fracture zone that continued at depth down into Glacier Valley,towards a developable site.TGH I-1 was drilled to 1,500 feet,and although it found evidence of an older geothermal system,the observed maximum temperature of only 186°F (80°C) indicates that it is located south of the presently active thermal region of Makushin Volcano. 200 400 600 800 1000 DEPTH(FEET)1200 1400 1600 1800 2000 150 FIGURE:3 MAKUSHIN STATIC TEMPERATURE PROFILES TEMPERATURE°F 200 250 300 350 400 PdN\ \ \et ennD-1 N\ 10 AGI E 1683 2.Exploratory Well Drilling The primary objective of the second (1983)project field season on Unalaska Island was the drilling of an exploratory wel]capable of producing geothermal fluids.As originally conceived,the project was to drill a full-size geothermal production well in the second field season.This plan was determined to be too expensive to undertake with the funds available, therefore,a "slim”well (Makushin ST-1)was programmed and designed to be drtiled to a maximum depth of 4,000 feet. Drilling of Makushin ST-1 began in June 1983 and proceeded through assorted volcanic rock types down to a depth of 136 feet,at which point the gabbro pluton was first penetrated.Coring proceeded into the pluton,7-inch casing was cemented in the well at the depth of 160 feet,and the coring of a smaller diameter hole was begun.On July 18,while coring at 670 feet,the bit dropped free for one foot and all circulation was lost.Because these conditions are characteristic of a possible resource-producing interval,the zone was tested. Flow-testing this zone indicated it to be a 325°F low-pressure steam zone of apparently noncommercial magnitude.The decision was made to plug the interval with cement and to deepen the hole in search of a more productive horizon.Coring continued with only minor lost circulation noted until a depth of 1,916 feet where all circulation was lost for a brief period. Coring was continued to 1,924 feet where returns were again lost.An additional two feet were cored "blind”to 1,926 feet with the well on vacuum.Republic then dectded to flow test the 1,916 to 1,926-foot interval. The results of this test were that only intermittent Flows of muddy water and steam were achieved.Coring operations were continued,all returns were again lost,and the well was cored "blind"from 1,926 feet to 1,946 feet.At 1,946 feet the core bit dropped three feet to a depth of 1,949 feet.This event prompted the decision to conduct a third flow test. At 7:45 a.m.on August 26,the wellhead valves were opened and the pressure immediately bled to 0 psig as the well unloaded muddy water and steam intermittently for approximately one hour.The well then ceased to flow and was shut in.When the wellhead pressure had risen to 25 psig,the master valves were again opened and the well flowed for one hour in a fashion similar to that exhibited during the preceding period.Maximum reading thermometers were run down the hole and 315°F was measured at a depth of 680 feet.Then two successive temperature instrument runs to 1,949 feet recorded 388°F and 395°F.The well was shut in at 4:00 p.m. On August 27 at 7:40 a.m.,the wellhead pressure had increased to 33.5 psig. The well was opened for a third time and after about one minute of modest Flow,a very strong flow of steam and water continued at a visually estimated rate of 30,000 lb/hr until the wel}was shut in at 10:40 a.m.Following this very successful preliminary flow test,the decision was made to install flow-line,metering,sampling,and survey equipment for a production test. im C.RESOURCE TESTING Makuskin Well ST-1 now has been production flow tested two times;the first period (during Phase II)was for 4 days in early September,1983,the second period was for 34 days from July 5 through August 8,1984 during Phase III project operations. 1.Test Facitities and Instrumentation A relatively simple two-phase orifice meter and James tube were installed at the end of a flow line to measure the flow rate.Upstream and downstream orifice pressures were recorded continuously with a differential pressure flow meter.James tube lip pressure was monitored continuously and recorded at frequent intervals using a carefully pre-calibrated test quality gauge. Pressure and temperature were also recorded frequently at the wellhead and elsewhere in the system.The fluid enthalpy was determined by both the two-phase orifice pressure drop data and by estimation from the measured pre-flash flowing wellbore temperature adjusted for estimated uphole heat losses. During the first (1983)flow period downhole pressure and temperature were measured using conventional Amerada instruments modified for high temperature service.In 1984 significantly improved instrumentation was acquired and utilized.The pressure monitoring equipment was a capillary tube system which utilizes a helium-filled,volumetric chamber downhole connected by a very smal]diameter capillary tube with a surface recording pressure transducer.This equipment has an accuracy of approximately 0.3 psi,with a sensitivity of 0.1 psi on the transducer.The temperature measurements were obtained using a thermocouple cable system with an accuracy of +3°F and a sensitivity of +3/4°F. 2.Flow Test Measurements The first production test of ST-1 was performed in five steps consisting of: 1)initial static pressure/temperature (P/T)profile and bottomhole surveys; 2)flow until stable at the highest practical rate with bottomhole P/T measurements during the rate change;3)flow at a reduced rate until stable with bottomhole P/T measurements during the rate change;4)shut in and buildup with two pressure instruments on bottom;and 5)final static P/T surveys. The initial static P/T surveys indicated that there is a shallow zone of underpressured (77 psig)steam at a temperature of .about 330°F (165°C) extending from a depth of 300 ft.down to the reservoir's water level at 700 ft.Below that level static temperatures gradually increased to a maximum of 378°F (192°C)at 1700 ft.,with a slightly lower temperature of 376°F (191°C) and a pressure of 482 psig recorded on bottom (1949 ft.).The maximum stabilized flow rate measured was 47,000 lb/hr of steam and hot water,ata wellhead pressure of 36 psig.The flow rate was then intentionally reduced 12 to 34,700 Ib/hr by partly closing the surface valve,which increased the wellhead pressure to 52 psig.Downhole P/T surveys recorded during and after flow indicated that the fluids produced entered the well within the 1900-1949 ft.depth interval at a temperature of 380°F.The available Amerada instruments could not accurately measure the much lower than anticipated bottomhole pressure changes,which were indicated to be only about 10 psi. The second production test of ST-1 was similar in basic plan to the First. The important differences were that it was conducted with extremely sensitive instrumentation and was performed over a substantially longer flow period. Initial static pressure/temperature surveys reconfirmed the location of the shallow steam zone and more precisely determined its temperature to be at 326.5°F (163.6°C)down to the steam/water interface at 810 feet (see Figure 4).Static temperatures gradually increased below that level, reaching a maximum of 399.8°F (204.3°C)at 1500 feet,with a slightly lower temperature of 394.7°F (201.5°C)and a pressure of 493.7 psig recorded on bottom at 1949 ft.The well was then allowed to flow at a 33,000 Ib/hr (throttled)rate for 15 days,and then fully opened to achteve maximum stabilized flow rate of 63,000 lb/hr at.a wellhead pressure of 27 psig for an additional 19 days.Temperature surveys conducted during flow periods indicated that the deep reservoir water entering the well is 379.6°F (193.1°C).The observed pressure drawdown during the first stage (low-rate) flow period was on the order of one psi,where,during the second (maximum rate)flow period,it was about two psi.After the well was shut in,the pressure tool recordedthe buildup data for the next 17 days without showingasignificantincreaseinbottomholepressure. 3.Reservoir Fluid Composition The chemical analyses of the flashed samples have been combined with the physical measurements to calculate the composition of reservoir Fluid.The physical measurements indicate that a 16 percent flash to atmosphere was occurring during the 47,000 lb/hr rate test.The back calculated reservoir fluid's composition is: CALCULATED RESERVOIR FLUID COMPOSITION S109 388 mg/] Ca 130 mg/1 Na 1,802 mg/] K 239 mg/1 HCO03 12 mg/1 $04 64 mg/] C1 3,116 mg/1 F 0.85 mq/] As 10.4 mg/1 Li 7.1 mg/I B 63 mg/1 Br 10 mg/1 TOS 6,000 mg/1 13 oTFIGURE:4 MAKUSHIN WELL ST 1 Temperature Survey Results TEMPERATURE °F 360 370 380 390 400350 i Nees TEMPERATURE (July 20,1984)id N iw STATIC TEMPERATURE (July 3,1984) RGI E 1685 The stable isotope analyses suggest that ground waters originating on the flanks of Makushin Volcano percolate downward to become the liquid within the geothermal reservoir.The isotope values clearly idicate that seawater isnotacomponentinthereservoir.The 5180 shift towards heavier values shows that hydrothermal alteration of the reservoir rock is occurring.This rock-water interaction allows exchange of oxygen isotopes between the water and the silicate minerals. 4.Interpretation of ST-1 Test Results In ST-1 produced fluid enters the wellbore at the bottom of the well,near 1,950 feet,at a temperature of 380°F,which ts less than the 395°F static temperature in the wellbore at that level.This indicates that the slightly (15°F)cooler water is entering the well through a fracture zone that connects the well with some other (cooler)area of the reservoir.During shutin,the cooler water is restricted from flowing toward the wellbore, allowing the well to heat up to its observed static condition.This means that the fluid density within the wellbore column lightens over a period of time as it returns to its static temperature level,and thus reduces the measured pressure buildup. The maximum stabilized flow rate of 63,000 Ibs/hr by a resource at 380°F is the maximum physically attainable from a well of the smal}(3 inch) dimensions of Makushin ST-1.The calculated productivity index of 32,000 lb/hr/psi indicates that the Makushin reservoir is extremely productive. This point is discussed further in the "Estimated Electrical Generating Potential"section of this report. 15 D.RESERVOIR DELINEATION The 1983 discovery of a significant geothermal resource by well ST-1 dictated that considerable effort be made during 1984 to further delineate the boundaries of that reservoir,in particular its northeastern boundary,in hopes that potential development sites could be identified closer to Dutch Harbor.Two operations were conducted;a fourth temperature gradient hole was drilled,located 1.2 miles north-northeast of ST-1,and a ground-surface resistivity survey of 11 square mile size was made.This survey covers the vicinity of ST-1 and the area extending 4 miles northeast of this well,down into lower Makushin Valley. 1.Drilling of Temperature Gradient Hole "A-1" The location of TGH "A-1"was controlled by the objective to drill the most promising resource site to be found on the relatively easily accessible plateau region near Sugarloaf Cone.This plateau is separated from ST-1 by two deep tributary canyons of the Makushin River,the significance being that by avoiding their crossing,the costs of road construction to resource development site could be materially reduced.Consequently,TGH "A-1"was sited at the plateau location closest to ST-1 and still within the same NE-SE structural-resource trend that includes most of the Makushin volcano thermal manifestations. Drilling rtg equipment stored tn Dutch Harbor over the winter was mobilized by helicopter to the "A-1"drill site and drilling began on June 22,1984. About 100 feet of young surface volcanics were cored through,below which are 1500 feet of.Unalaska formation Miocene flows and volcanic agglomerate units above the Makushin gabbro.At the final drilled depth of 1867 feet the hole was still in gabbro. A temperature survey acquired on October 8,40 days after completion, indicated that the bottomhole temperature was about 375°F.This is almost equal to the equilibrated temperature results obtained itn both ST-1 and TGH "E-1".However,no evidence of effective fracturing exists within the 265 feet of gabbro in the bottom of "A-1",meaning that if a significant geothermal reservoir is present at this site,it must Tite still deeper. 2.Electrical Resistivity Survey An "E-SCAN"electrical resistivity survey was carried out in the Makushin Geothermal project area during the summer of 1984.Approximately 11 square miles were surveyed,covering all of the potentially developable area within the upper Makushin Valley,and extending down into lower Makushin Valley. The survey examined in detail]the area known to be underlain by the geothermal reservoir discovered by ST-1,and was used to obtain evidence as to the location of that reservoir's boundaries.In addition,a search was made for any evidence that a geothermal reservoir 1s present within the physically more accessible areas located northeast of ST-1,toward Dutch Harbor., 16 The survey results reveal that the gabbroic geothermal reservoir rock in ST-1 has an apparent resistivity of about 100 ohm-meters.In lower Makushin Valley,4 miles to the northeast,the same intrusive rocks are three times more resistive,indicating significantly less hydrothermal alteration,lower temperatures,and the probable absence of a geothermal reservoir at reasonably comparable depths. An examination and interpretation of the resistivity data for all of the area in between,and in all directions around ST-1,clearly shows that the southern and western limits of the known geothermal reservoir extend for at least a mile from ST-1 in those directions,beyond the surveyed area.To the southwest of ST-1]resistivity values for the 200-1000 meter (650-3300 Ft.) depth interval are in the range of 30 to 100 ohm-meters. There 1s now considerable evidence that the ST-1 reservoir extends only an additional 1000 to 2000 feet to the northeast of the well,where resistivity values abruptly increase to 200-300 ohm-meters (see Figure 5).This increase is attributed to the presence of a fault boundary separating the two areas, with extensive hydrothermal alteration and the shallow geothermal reservoir limited to only the southwest (low resistivity)side. Based on the interpreted results of both TGH "A-1"and the resistivity survey,it is now recommended that development plans anticipate future production and injection wells will be drilled in relatively close proximity to ST-1,and not (unfortunately)significantly closer to Dutch Harbor.This recommendation could ultimately be proven to have been overly conservative, in unnecessarily restricting the area now considered potentially available for resource development.It 1s,however,judged to be the most responsible interpretation that can presently be made,in light of all the data available. W7 8TREPUBLIC GEOTHERMAL INC. 17 cosets Susest aaa 4 onan Sa UNAL ASKA A u E FAULT em EE OAS ....GEQTHERMAL EXPLORATIONthteaeeTEDINayomerUROESSPanPROJECT UNALASKA ISLAND,ALASKA E-SCAN RESISTIVITY SURVEY MAKUSHIN VOLCANO AREA JULY,AUGUST,1984 SUMMARY OF SURVEY FINDINGS, PRELIMINARY INTERPRETATION COMPLETED. KEY TO REFERENCES IN REPORT RESISTIVITY CONTACT OR FAULT IMPLICATION DERIVED FROM SHALLOW {(<700 METERS) DATA ONLY.NO STRUCTURAL INFERENCES FROM DEEPER DATA ARE SHOWN. +SURVEY ELECTRODE SITE KAA es @ -'DATLL_HOLE SITEApNanereeraatacreMeeBagedPeKILOMETERS i. ean,FM:tort 0 0.5 4 1.5 L i]}=THOUSAND FEET 2 3 4 °|}i iI - PREMIER GEOPHYSICS INC. VANCOUVER,CANADA FIGURE:5 E.THE MAKUSHIN VALLEY GEOTHERMAL RESERVOIR MODEL The heat source available for any Makushin geothermal system ts the buried, partly molten,magma body that is genetically related to the Makushin volcanic suite.This heat source was still molten after the last glacial period,approximately 3,000-4,000 years ago,and the 14 historic eruptions of Makushin Volcano suggest that molten or semi-molten rock is likely to still exist beneath the mountain. The mechanism for enthalypy transfer from this heat source to a Makushin geothermal system is dominantly conductive heat flow.This is indicated by the stable isotopes of the thermal waters,the isotopic composition of steam from Makushin's summit,and the carbon isotopes of fumarolic methane. The Makushin geothermal system discovered in upper Makushin Valley is a 380°F Jiquid-dominated resource,consisting of a simple NaCl type water of relatively low salinity having 6000 ppm of dissolved solids.The reservoir waters rise upward (convect)and boil at an elevation of about 1,100 feet in localized open fractures to form a steam cap that is limited in size and extent.Leakage of steam from this cap feeds fumaroles and mixes with ground waters to form chloride-poor thermal waters.Reservoir waters also mix with ground waters before surfacing as chloritde-rich hot springs in Glacier Valley and in Driftwood Bay valley. This Makushin geothermal reservoir is situated primarily within the Makushin gabbroic stock at commercially exploitable depths.However,it is possible that beneath and to the west of Makushin Volcano's summit crater another reservoir or reservoirs may exist within the Makushin Volcanics or the Unalaska Formation rocks.An impermeable seal for the reservoir exists, comprised of clayey,altered volcanic rocks,and chemical precipitates which have "self-sealed"the gabbro,as seen in temperature gradient hole E-1 and Makushin ST-1. The specific location of the discovered Makushin geothermal reservoir within the gabbro stock is structurally controlled by a major northeasterly striking fracture zone.Contemporary seismicity and recent movement along this northeast-trending zone maintains the permeability of the fractures in the present-day geothermal reservoir,and in the impermeable cap along which the majority of the surface geothermal manifestations occur. There are two subparallel structures that intersect the northeast-trending zone and which expand the area of the Makushin geothermal reservoir.These are an inconspicuous east-west striking fracture zone that expands the reservoir beneath Fumarole Fields #3,#4,#5,and #23,and a northwest- trending fracture on the south edge of Fox Canyon that may extend the reservoir towards Fumarole Field #7.Assuming that these three fracture systems control the extent of the resource,the commercially exploitable reservoir in the Makushin geothermal area might well cover approximately 5 square miles. 19 4,CONCLUSIONS FOR COMMERCIALIZATION A.ESTIMATED ELECTRICAL GENERATING POTENTIAL 1.Well Production Potential Well ST-1 has been demonstrated to produce 63,000 lb/hr steam and hot water at a wellhead pressure of 42 psia.That production could be used to operate a 400 kilowatt electricity generator.However,as pointed out previously, the flow rate of ST-1 is severely limited by the small (3 inch)diameter of the well.Significantly larger production rates and greater electricity generating potential could be achieved from a larger diameter commercial size well.Fortunately,computer programs are available to make such production rate predictions,based on factors determined initially by small diameter well performance. A wellbore flow model yielding wellhead pressure vs flow rate must first be validated against the measured slim hole conditions.Once a match is achieved,then wellhead pressure vs flow rate curves for various commercial-size wellbore configurations may be generated and related to appropriate power cycles with some degree of confidence. The flow simulator used in this study is a vertical,multiphase flow simulator which incorporates variable well diameter with depth,heat losses, and noncondensable gases.The "nominal”commercial well conditions arrived at were as follows: Initial Pressure 494 psig at 1,949 feet 379°F at 1,949 feet 6,000 ppm TDS 200 ppm 31,500 Ib/hr/psi 13-3/8 and 16 inch Inflow Temperature Salinity co,Content Productivity Index Wellbore Size Using these conditions,simulator-generated curves for wellhead pressure vs flow rate were constructed for the two different wellbore sizes.Ata reasonably optimum wellhead pressure of 55 psig (for power generation from this resource),flow rates of 1,220,000 and 1,920,000 Ib/hr are predicted for the wellbore sizes of 13-3/8"and 16"respectively. 2.Well Power Potential Using the above predicted flow rate data for commercial size wells,the electrical power generation potential of a single well can be estimated. Based on figures presented later in the commercialization section of this report,a commercial size well at Makushin can have an electrical generating 20 potential of between 6,200 and 14,100 kilowatts (6.2 to 14.1 megawatts),depending on its diameter,the selected flow rate (or WHP),and the type of power cycle selected. 3.Reserve Estimation The last step is to estimate the size of the Makushin reservoir,in terms of the amount of hot water available.That reserve estimate can then be used to predict for how many years a commercial size well could continuously produce and generate electricity. Material balance calculations for reserve estimation of systems such as the Makushin geothermal reservoir have been developed and used by a number of investigators.The initiating step is an expression providing the isothermal compressibility. c=-1 av (1) Va.Tp Assuming that the total compressibility of the system is constant,Equation 1 may be integrated: V2 =ecdp :(2) Vy and because the recovery in terms of reservoir volumes is defined as: r =V2-Vy (3) Vy then a combination of Equations 2 and 3 results in: Va-Vy =ecAp -] Vy The cumulative production in terms of reservoir volumes is,of course, Vo-V]and,because the fluid 1s considered incompressible,the ratio V2-V1 (4) Vy . may be taken as: Wp W which ts the ratio of the cumulative mass produced to the initial mass-in-place.Hence,Equation 4 becomes: 21 Wp =e(cAp)1 (5) W Using Equation 5,the initial-fluid-in-place may then be calculated: 4.06 x 107=e(6 x 10-6 x1)1} WW yielding W =6.8 x 1012 Ibs.Given the uncertainties inherent in this calculation,the value of "W"can be constdered order of magnitude only. Nonetheless,assuming a single full-size production well drilled on the site of ST-1 yielding 1,500,000 lb/hr,and (depending on the power cycle used) generating 6-14 MWe,the longevity of this reservoir is extremely large.The calculated initial-mass-in-place indicates that the Makushin reservoir could deliver this flow rate for over 500 years. 22 B.RESOURCE COMMERCIALIZATION 1.Power Conversion Processes The conversion of hydrothermal energy from a Makushin-type liquid-dominated geothermal resource into electric power can be accomplished by any one of the following technologically proven processes: Flash Steam In the flash steam process,steam is produced from the geothermal fluid by reducing the pressure of the fluid below the saturated liquid pressure.The steam is then used to directly power a turbine,which in turn drives an electric generator.Both single and double flash systems are available. Binary In the binary process,a low boiling point fluid,such as freon or isobutane,is passed through a heat exchanger where it is vaporized by proximity to the geothermal brine.The superheated vapor is then used to power a turbine,which in turn drives an electric generator. Hybrid In the hybrid process,part of the geothermal Fluid is Flashed into steam which is used to drive a steam turbine-generator.The residual fluid is then used to vaporize a low boiling point Fluid through a heat exchanger.The superheated vapor produced is then used to power a second turbine-generator. Total Flow In the total flow process,all of the geothermal fluid 4s expanded through a mechanical device which converts both thermal and kinetic energy of the well fluid into shaft work (torque).This shaft work is then used to drive an electric generator. Figure 6 illustrates the relative efficiencies of the five available power conversion systems.For example,at a wellhead pressure of 72 psia,the same well flow of 1,200,000 tb/hr can be used to generate 5.8 MW by using the single flash steam process,or 7.3 MW with the double flash process,or 7.75 MW with the total flow process,or a maximum of 9.0 MW by using either the binary or hybrid cycle process. 23 FIGURE:6 POTENTIAL NET POWER GENERATION OF A MAKUSHIN PRODUCTION WELL (With 13 3/8”diameter casing) 12 == MW - NOILVY3N39 Y3MOd LIN TWILN3SLOd o- ao ©w< oO N = o 3LVY MO14d WOAWIXVA Ate. LE|"" 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 130 120 110 2°°o- [=]Sooo °o 8a ©wvt VISd - JHNSS3Yd GV3HT13M 20 10 WELL FLOW (In 1000 Ibs/hr) AGI E 1684 24 2.Load Forecasts The electrical load forecasts for Unalaska and Dutch Harbor have recently been developed as part of a reconnaissance study for the Alaska Power Authority.Two cases were considered in this study.One case assumes that load demands will remain constant ("level")indefinitely.The other case assumes that the load demands wil]increase at about a 4%rate until 1995, after which demand will grow at about a 7%rate.Figure 7 shows both the average load and maximum load demands assumed for these two cases. 3.Unit Sizing and Scheduling It is anticipated that a new geothermal power plant installation would be intertied with the existing conventional power plants to supply the electrical power needs of Unalaska and Dutch Harbor. The geothermal power plant would be scheduled to begin commercial operation in January 1989.Upon completion,the geothermal power plant would primarily provide base load power while the conventional diesel generators would be used to provide peak load and emergency power. Due to the remoteness of the geothermal construction site,the difficult site access and the need for high reliability,the geothermal power plant would be unitized.The size,number and phasing schedule of the geothermal units for each of the power conversion processes studied were determined by an evaluation of commercially available units,the power demand forecasts,and the intent that when all installed units are available for power generation, the net generating capacity of the geothermal units will always be kept above the electrical system base load demand.In order to meet the electrical system load demands estimated up to the year 2000 for both the "level demand" and "increasing demand"cases,a geothermal power plant using any one of five different power conversion cycles studied could be used. 4.Geothermal Power Development Cost Comparisons A comparison of the major capital cost items required to develop geothermal power using each of the five alternative processes considered for both "Level Demand"and "Increasing Demand"cases are shown on Tables J]and 2.Each power development alternative includes power plant costs and assoctated major field development costs.The additional costs for infrastructure items,such as road and transmission line,are not included here as they are identical for all alternatives.Costs are in 1984 dollars. Power plant engineering and fabrication costs include engineering,shop fabrication and testing of power modules,prefabrication of auxilfary systems,and transportation to Driftwood Bay.Power plant construction costs include transportation from Driftwood Bay to jobsite,construction camp, construction labor,and construction management. 25 97ELECTRICALPOWERDEMAND-MWFIGURE:7 UNALASKA ISLAND AVERAGE AND MAXIMUM POWER DEMANDS AS ESTIMATED BY ACRES AMERICAN INC. |CS GS CS CO CO CS NU i {4 L ! 1988 1990 1992 1994 1996 1998 YEARS 2000 2002 2004 AGI E 1682 76ELECTRICALPOWERDEMAND-MWFIGURE:7 UNALASKA ISLAND AVERAGE AND MAXIMUM POWER DEMANDS AS ESTIMATED BY ACRES AMERICAN INC. "LEVEL”AVERAGE POWER DEMAND a Ee SOS SN SS NS CN OS GN MG PONG CNN CS CONUS EN OS1984198619881990199219941996199820002002 2004 YEARS AGI E 1682 LeTABLE 1 GEOTHERMAL POWER DEVELOPMENT CAPITAL COST COMPARISONS LEVEL DEMAND DEVELOPMENT CASE (Thousands of 1984 Dollars) Single Flash Double Flash Total Flow Steam Plant.Steam Plant Binary Plant Hybrid Plant Plant Power Plant Net Generating Capacity 10 MW 10 MW 6.7 MW 10 MW 10 MW Number of Power Generation Units 2 2 2 3 2 Power Plant Engineering and Fabrication Costs 14,820 17,000 8,590 14,520 18,720 Power Plant Construction Costs 21,800 24,800 11,440 20,080 27,200 Subtotal Installed Power Plant Costs 36,620 41,800 20,030 34,600 45,920 Number of Production Wells Provided 2 2 1 2 2 Number of Injection Wells Provided 1 |1 T 1 Production Well Costs 6,099 6,099 3,747 6,099 6,099 Injection Well Costs 1,600 1,600 1,600 1,600 1,600 Production Pipeline Costs 963 963 610 963 963 Injection Pipeline Costs ___580 ___302 ___302 ___302 ___302 Subtotal Field Development Costs 9,242 8,964 6,259 8,964 8,964 Total Geothermal Power Development Costs 45,862 50,764 26,289 43,564 54,884 Cost Per MW of Net Power Generated 4,586 5,076 3,924 4,356 5,488 8TABLE 2 GEOTHERMAL POWER DEVELOPMENT CAPITAL COST COMPARISONS INCREASING DEMAND DEVELOPMENT CASE Power Plant Net Generating Capacity Number of Power Generation Units Power Plant Engineering and Fabrication Costs Power Plant Construction Costs Subtotal Installed Power Plant Costs Number of Production Wells Provided Number of Injection Wells Provided Production Well Costs Injection Well Costs Production Pipeline Costs Injectton Pipeline Costs Subtotal Field Development Costs Total Geothermal Power Development Costs Cost Per MW of Net Power Generated (Thousands of 1984 Dollars) Single Flash Double Flash Total Flow Steam Plant Steam Plant Binary Plant Hybrid Plant Plant 20 MW 20 MW 20 MW 20 MW 20 MW 4 4 6 6 4 28,160 32,300 25,770 29,040 37,440 41,420 47,120 =34,320 =40,160 =_54,400 69,580 79,420 60,090 69,200 91,840 4 3 3 3 3 2 2 2 2 2 13,593 11,241 11,241 11,241 11,241 3,200 3,200 3,200 3,200 3,200 2,380 1,830 1,830 1,830 1,830 _1,080 900 604 604 900 20,253 17,171 16,875 16,875 17,171 89,833 96,591 76,965 =86,075 =109,011 4,492 4,830 3,848 4,304 5,451 Associated field development costs are composed of 13-3/8"production and injection well costs which include drilling,completion,and short testing of al?wells to be provided to supply and dispose of the geothermal fluid flow required by the power plant,plus the production and injection pipeline costs,which include engineering and construction of insulated and non-insulated pipeline between the wells and the power plant,and injection pumps. 5.Power Conversion Process Recommendation Considering the positive and negative aspects of each cycle considered,the binary cycle is recommended as the best power conversion process to generate electricity from the Makushin resource for the following reasons: 1.It is the most economical process for the smaJ](5 to 20 MW)base load demand of the Unalaska electrical system. 2.It is an efficient power conversion process requiring relatively small field development to support the power plant. 3.While it has not yet been as widely used as the flash steam process, it is easily developed in small units,adding reliability to the overall plant. 4.It can be prefabricated in small,shop assembled and tested modules that can be easily transported and installed. 5.It can be easily automated to require minimal operating supervision. 6.It does not incur a risk of freezing during winter months operation. 7.It can be installed quickly,adding scheduling flexibility if power demand increases faster than expected. 6.Binary System Development Costs Republic Geothermal,Inc.has prepared Tables 3-5 showing the total capital cost estimates and the operation and maintenance cost estimates for both the 6.7 MW (net)and the 20 MW (net)scenario.All cost estimates are based on the use of the recommended binary cycle for power generation,and include all major project items such as road construction,installment of a buried transmission line,plus escalation and interest during construction. 29 oeTABLE 3 UNALASKA 10 MW GROSS (6.7 MW NET)FIELD AND BINARY POWER PLANT DEVELOPMENT COSTS Field Development Costs (1984) Production Well (1) Injection Well (1) Well Testing Direct Operation &Maintenance Home Office Start-Up Subtotal Field Costs Power Plant Costs (1984) Power Plant Eng.&Const. Production Pipeline Injection Pipeline Spare Parts Consulting &Coordination Start-Up Insurance Subtotal Power Plant Costs Other Costs (1984) Road Construction Transmission Line Subtotal Other Costs TOTAL 1984 COSTS Escalation (6.5%Per Year) TOTAL ESCALATED COSTS Interest Expenses (10%Per Year) TOTAL DEVELOPMENT COSTS Equity Debt TOTAL USE OF FUNDS LEVEL DEMAND DEVELOPMENT CASE (Thousands of 1984 Dollars) 1986 1987 =&ownoowoocoeTotal Costs LoTABLE 4 UNALASKA 30 MW GROSS (20 MW NET)FIELD AND BINARY POWER PLANT DEVELOPMENT COSTS INCREASING DEMAND DEVELOPMENT CASE (Thousands of 1984 Dollars) Total Costs Total Costs Total Costs Total Costs 1986 1987 1988 =First Phase 1991 1992 Second Phase 1998 1999 Third Phase All Phases Field Development Costs (1984) Production Wells (3)3,747 0 0 3,747 3,747 0 3,747 3,747 0 3,747 11,241 Injection Wells (2)1,600 0 0 1,600 0 0 0 1,600 0 1,600 3,200 Well Testing 521 0 0 §21 236 0 236 354 0 354 VM Direct Operation and Maintenance 513 453 734 1,700 513 734 1,247 526 734 1,260 4,207 Home Office 475 400 525 1,400 475 525 1,000 475 525 1,000 3,400 Start-Up 0 0 210 210 0 150 150 0 100 100 460 Subtotal Field Costs 6,856 853 1,469 9,178 4,971 1,409 6,380 6,702 1,359 8,06)23,619 Power Plant Costs (1984) Power Plant Engineering &Construction 1,000 10,516 8,514 20,030 10,015 10,015 20,030 10,015 10,015 20,030 60,090 Production Pipeline 0 0 610 610 0 610 610 0 610 610 1,830 Injection Pipeline 0 0 302 302 0 0 0 0 302 302 604 Spare Parts 0 0 200 200 0 200 200 0 200 200 600 Consulting and Coordination 162 200 238 600 200 200 *400 200 200 400 1,400 Start-Up 0 0 400 400 0 200 *200 0 150 150 750 Insurance 0 100 130 230 0 130 130 0 130 130 490 Subtotal Power Plant Costs 1,162 10,816 10,394 22,372 10,215 113,355 21,570 10,215 13,607 21,822 65,764 Other Costs (1984) Road Construction O 5,146 0 5,146 0 0 0 0 0 0 5,146 Transmission Line 0 0 6,405 6,405 0 0 0 0 0 6 6,405 Subtotal Other Costs O 5,146 6,405 17,551 0 0 0 0 0 0 11,551 TOTAL 3984 COSTS 8,018 16,815 18,268 43,101 15,186 12,764 27,950 16,917 12,966 29 ,883 100,934 Escalation (6.5%Per Year)1,076 3,497 5,233 9,806 8,413 8,360 16,773 23,935 20,380 44,315 70 ,894 TOTAL ESCALATED COSTS 9,094 20,312 23,50)52,907 23,599 21,124 44,723 40,852 33,346 74,198 171,828 e Interest Expenses (10%Per Year)274 =#1,240 2,703 4,217 709 2,210 2,919 1,226 3,724 4,950 12,086 TOTAL DEVELOPMENT COSTS 9,368 21,552 26,204 57,124 24,308 23,334 47 ,642 42,078 37,070 79,148 183,914 Equity 4,684 10,776 13,102 28,562 12,154 11,667 23,821 21,039 18,535 39,574 91,957 Debt 4,684 10,776 13,102 28,562 12,154 11,667 23,821 21,039 18,535 39,574 91,957 TOTAL USE OF FUNDS 9,368 21,552 26,204 57,124 24,308 23,334 47,642 42,078 37,070 79,148 183,914 ceTABLE 5 UNALASKA BINARY POWER PLANT COMBINED PLANT AND FIELD ANNUAL OPERATION AND MAINTENANCE COSTS (Thousands of 1984 Dollars) POWER PLANT SIZE 10 MW (GROSS)30 MW (GROSS) Administration 85 170 Operation and Maintenance Labor 580 7190 Contract Maintenance , 350 650 Well Reconditioning 75 225 Outside Consulting 150 150 Power Plant Insurance 100 300 Miscellaneous _460 , 550 TOTAL ANNUAL COST 1,800 2,835 Conclusions the strength of this study,the following conclustons can be drawn: The Makushin geothermal resource can be utilized to generate electrical power for the cities of Dutch Harbor and Unalaska. Geothermal power is best suited to meet the baseload demand of the electrical system.Peak loads can be more economically met by use of conventtonal diesel generators,as required. The binary cycle is the economically and technically preferred power conversion process to generate electricity from the Makushin geothermal resource. A 10 MW gross (6.7 MW net)geothermal power development would satisfy the "level demand"average load forecast case indefinitely.Recommended development would consist of two identical 5 MW gross binary units together with one production and one injection well. The 10 MW gross geothermal power development could be commercial by January 1989 and would cost a total of $57,124,000. A 30 MW gross (20 MW net)geothermal power development would satisfy the "increasing demand”average load forecast case for at least the next 20 years.It 1s recommended that such a power plant be developed in three phases timed to the growth in demand.The first phase of development would be exactly the same as the 10 MW gross case,to be operational in January,1989.The second phase of development would consist of essentially duplicating the initial phase and would become commercial in January,1993.The third phase of development would consist of two additional binary units identical to the units provided in phases 1 and 2 together with one production and one injection well starting commercial operation in January 2000. A 30 MW gross geothermal power development as outlined above would cost a total of $183,914,000. 33