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Pressure drawdown analysis for the Travale 22 well

Description: This work presents preliminary results on the analysis of drawdown data for Travale 22. Both wellhead pressure and flow rate data were recorded in this well for over a period of almost two years. In the past, Barelli et al. (1975) and Atkinson et al. (1977) presented the analysis of five pressure buildup tests. Figure 1 shows the Horner plot for these cases. They found that to have a good match in all cases, it was necessary to assume that the Travale 22 well is intersected by a partially penetrating vertical fracture in a parallel-piped whose bottom side is maintained at constant pressure (boiling front), as shown in Fig. 2. Atkinson et al. also presented an analysis for a pressure interface test run in the Travale-Radicondoli area. In this case, the Travale 22 well was flowing and the pressure recorded at wells R1, R3, R5, R6, R9, and Chl (see Fig. 3 ) . Analysis of these data showed that pressure interference in this reservoir can be matched by considering pure linear flow (Figs. 4 and 5 ) . This indicated the possible presence of a vertical fracture intersecting the Travale 22 well. It was determined that fracture is oriented along the N73{sup o}W direction. In addition, the pressure interference data showed that no boundary exists within 2 kilometers from the fracture plane. It was mentioned that linear flow should take place in both horizontal and vertical directions.
Date: January 1, 1978
Creator: Barelli, A.; Brigham, W.E.; Cinco, H.; Economides, M.; Miller, F.G.; Ramey, H.J., Jr. et al.
Partner: UNT Libraries Government Documents Department

Pressure Profiles in Two-Phase Geothermal Wells: Comparison of Field Data and Model Calculations

Description: Increased confidence in the predictive power of two-phase correlations is a vital part of wellbore deliverability and deposition studies for geothermal wells. Previously, the Orkiszewski (1967) set of correlations has been recommended by many investigators to analyze geothermal wellbore performance. In this study, we use measured flowing pressure profile data from ten geothermal wells around the world, covering a wide range of flowrate, fluid enthalpy, wellhead pressure and well depth. We compare measured and calculated pressure profiles using the Orkiszewski (1967) correlations.
Date: January 21, 1986
Creator: Ambastha, A.K. & Gudmundsson, J.S.
Partner: UNT Libraries Government Documents Department

A Method to Recover Useful Geothermal-Reservoir Parameters from Production Characteristic Curves (1) Steam Reservoirs

Description: In this paper we develop and demonstrate a method to estimate the reservoir pressure and a productivity index for vertical steam wells, from its production characteristic (also called output) curves. In addition, the method allows to estimate the radius of influence of the well, provided that a value of the reservoir transmisivity is available. The basic structure of the present method is: first, the measured well head mass flowrates and pressures are transformed to downhole conditions by means of a numerical simulator; then, the computed downhole variables are fitted to a simple radial model that predicts the sandface flowrate in terms of the flowing pressure. For demonstration, the method was applied to several steam wells from the Los Azufres Geothermal field. We found excellent agreement of the model with this ample set of field data. As a bonus, the processed data allowed several inferences about the steam producing zone of the reservoir: that the wells considered produce from relatively isolated pockets of steam, which are probably fed by near-by inmobile water; and that these feed zones are in poor hydraulic communication with the field surface waters. our method are that it provides a way to retrieve important reservoir information from usually available production characteristic curves, and that the method works from easily and accurately taken wellhead measurements.
Date: December 15, 1983
Creator: Iglesias, E.; Arellano, V.; Garfias, A.; Miranda, C.; Hernandez, J. & Gonzalez, J.
Partner: UNT Libraries Government Documents Department

A Method to Recover Useful Geothermal-Reservoir Parameters from Production Characteristic Curves (2) Hot Water Reservoirs

Description: In this paper we develop and demonstrate a method to estimate the reservoir pressure, a mass productivity index, and a thermal power productivity index for vertical water-fed geothermal wells, from its production characteristic (also called output) curves. In addition, the method allows to estimate the radius of influence of the well, provided that a value of the reservoir transmisivity is available. The basic structure of the present method is: first, the measured wellhead mass flowrate; and pressures are transformed to downhole conditions by means of a numerical simulator; then, the computed downhole variables are fitted to a simple radial model that predicts the sandface flowrate in terms of the flowing pressure. For demonstration, the method was applied to several wells from the Cerro Prieto geothermal field. We found very good agreement of the model with this ample set of field data. The main advantages of our method are that it provides a way to retrieve important reservoir information from usually available production characteristic curves, that it works from easily and accurately taken wellhead measurements, and that its results address the two main aspects of geothermal resource utilization, namely, mass and heat production.
Date: December 15, 1983
Creator: Iglesias, E.; Arellano, V. & Molinar, R.
Partner: UNT Libraries Government Documents Department

Integrated Geothermal Well Testing: Test Objectives and Facilities

Description: A new and highly integrated geothermal well test program was designed for three geothermal operators in the US (MCR, RGI and Mapco Geothermal). This program required the design, construction and operation of new well test facilities. The main objectives of the test program and facilities are to investigate the critical potential and worst problems associated with the well and produced fluids in a period of approximately 30 days. Field and laboratory investigations are required to determine and quantify the problems of fluid production, utilization and reinjection. The facilities are designed to handle a flow rate from a geothermal well of one million pounds per hour at a wellhead temperature of approximately 268 C (515 F). The facilities will handle an entire spectrum of temperature and rate conditions up to these limits. All pertinent conditions for future fluid exploitations can be duplicated with these facilities, thus providing critical information at the very early stages of field development. The new well test facilities have been used to test high temperature, liquid-dominated geothermal wells in the Imperial Valley of California. The test facilities still have some problems which should be solvable. The accomplishments of this new and highly integrated geothermal well test program are described in this paper.
Date: January 1, 1981
Creator: Nicholson, R. W. & Vetter, O. J.
Partner: UNT Libraries Government Documents Department

Geothermal Resources Development - HGP-A Wellhead Generator Proof of Feasibility Project

Description: Project: A 3 MW plant with single flash steam system. Totally enclosed plant building integrated with a visitors' center, within a fully developed site. Location: Puna District, Island of Hawaii. Construction Cost: US $8,000,000. Completed: Schedule completion August 1980. (This plant was officially dedicated, July 17, 1981 and is currently delivering energy to HELCO Power System in Hawaii. HELCO is operating this plant for the University of Hawaii). Services: Concept studies, preliminary design, final design, procurement and construction management.
Date: August 1, 1980
Partner: UNT Libraries Government Documents Department

Thermal extraction analysis of five Los Azufres production wells

Description: Thermal energy extraction from five wells supplying 5-MWe wellhead generators in three zones of the Los Azufres geothermal field has been examined from production and chemical data compiled over 14-years of operation. The data, as annual means, are useful in observing small-scale changes in reservoir performance with continuous production. The chemical components are chloride for quality control and the geothermometer elements for reservoir temperatures. The flowrate and fluid enthalpy data are used to calculate the thermal extraction rates. Integration of these data provides an estimate of the total energy extracted from the zone surrounding the well. The combined production and chemical geothermometer data are used to model the produced fluid as coming from just-penetrating wells for which the annual produced mass originates from a series of concentric hemispheric shells moving out into the reservoir. Estimates are made of the drawdown distance into the reservoir and the far-field conditions.
Date: January 26, 1995
Creator: Kruger, Paul & Quijano, Luis
Partner: UNT Libraries Government Documents Department

Customized Well Test Methods for a Non-Customary Geothermal Well

Description: Recent testing of Thermal 4, The Geysers blowout well, has shown that the flow has two different components: a low enthalpy, mineral-laden flow from a well drilled within the existing wellhead and a high flowrate, high enthalpy annular flow. The commingled flows were mechanically separated and individually tested. The results of the test show that the flows are from two very different sources that are in weak hydraulic communication. Work is in progress to apply this information to bring Thermal 4 within compliance of the 1986 air quality regulations.
Date: January 21, 1986
Creator: Burr, Myron
Partner: UNT Libraries Government Documents Department

Worldwide Geothermal Power Plants: Status as of June 1980

Description: There are 100 geothermal power units now in operation throughout 12 countries, with a total installed capacity of just over 2110 MW. The average unit thus is rated at 21.1 MW. Newer units may be broadly classified as follows: (a) wellhead units of less than 5 MW; (b) small plants of about 10 MW; (c) medium plants of 30-35 MW; (d) large plants of about 55 MW; and (e) complexes typically consisting of several 55 MW units in a large geothermal field. There is a trend toward turbine units of the double-flow type with a 55 MW rating, used either alone or in a tandem-compound arrangement giving 110 MW in a single power house. This is particularly evident at The Geysers field in California. Double-flash units (separated-steam followed by a surface flash) are suited to high quality reservoirs having high temperature, high steam fractions at the wellhead, and low scaling potential. Single-flash units (separated steam) may be called for where scaling by the spent brine is a potential problem for the liquid disposal system. Binary plants are being used for some very low temperature reservoirs, particularly in the People's Republic of China, albeit in extremely small units. A large-scale pilot plant of the binary type is being planned for the Imperial Valley of California.
Date: December 1, 1980
Creator: DiPippo, Ronald
Partner: UNT Libraries Government Documents Department

Deliverability and its Effect on Geothermal Power Costs

Description: The deliverability of liquid-dominated geothermal reservoirs is presented in terms of reservoir performance, and wellbore performance. Water influx modeling is used to match the performance of Wairakei in New Zealand, arid Ahuachapan in El Salvador. The inflow performance is given in terms of a linear productivity index for liquid-only flow, and a solution-gas drive relationship for two-phase flow. A 9-5/8'' production well is assumed, flowing 250 C water from 900 m depth, with a wellhead pressure of 100 psia. A Geothermal Development Model, that couples reservoir deliverability and power plant performance, and assigns costs to both, is used to illustrate how the development cost of geothermal electric power projects can be estimated.
Date: January 21, 1986
Creator: Gudmundsson, J. S. & Marcou, J. A.
Partner: UNT Libraries Government Documents Department

Simulation of Radon Transport in Geothermal Reservoirs

Description: Numerical simulation of radon transport is a useful adjunct in the study of radon as an in situ tracer of hydrodynamic and thermodynamic numerical model has been developed to assist in the interpretation of field experiments. The model simulates transient response of radon concentration in wellhead geofluid as a function of prevailing reservoir conditions. The radon simulation model has been used to simulate radon concentration response during production drawdown and two flowrate transient tests in vapor-dominated systems. Comparison of model simulation with experimental data from field tests provides insight in the analysis of reservoir phenomena such as propagation of boiling fronts, and estimates of reservoir properties of porosity and permeability thickness.
Date: December 15, 1983
Creator: Semprini, Lewis & Kruger, Paul
Partner: UNT Libraries Government Documents Department

Assessment of the Geothermal Development of Mexico

Description: Mexico, with a 60 million population has an extension of almost 2 million square kilometers. A large number of volcanoes and hydrothermal manifestations are found in the area, particularly along the Pacific Coast. The electricity needs of this country require its installed capacity to be doubled every eight-and-a-half years. Although its main energy source is the hydrocarbons, new sources of energy are being investigated and developed. In 1973, at Cerro Prieto, a 75 MW plant was inaugurated utilizing geothermal steam, initiating in this way commercial exploitation of this energy. From there on an uninterrupted program of exploration and development has been followed, along and across the country. Probably the region with the highest potential of geothermal energy is the New-volcanic Belt, a zone 300 kilometers wide which crosses the country from the Pacific Coast to the Gulf of Mexico Coast. In this zone, the geothermal fields of Los Azufres, Los Negritos, Ixtlan de los Hervores, La Primavera and San Marcos are located. Sixteen wells have been drilled at Los Azufres, 14 good producers with an average temperature of 275 C. An area of 385 square kilometers is estimated can be exploited for steam production. By 1981, it is expected to have four wellhead turbogenerators rated 6 MW each. Two geothermal wells are now being drilled at La Primavera, with very good results. Temperatures of 275 C have been found at a depth of 800 m in the first well of the Rio Caliente module. The first two wells are now being drilled at Los Humeros geothermal zone. To date, 80 wells have been drilled at Cerro Prieto. In the last group of wells the producing stratum was found at a depth between 2000 and 3000 m. The temperature of this stratum is about 340 C, and each well has an ...
Date: December 1, 1980
Creator: Dominguez, B.; Bermejo, F. & Guiza, J.
Partner: UNT Libraries Government Documents Department

INITIAL CHEMICAL AND RESERVOIR CONDITIONS AT LOS AZUFRES WELLHEAD POWER PLANT STARTUP

Description: One of the major concerns of electric utilities in installing geothermal power plants is not only the longevity of the steam supply, but also the potential for changes in thermodynamic properties of the resource that might reduce the conversion efficiency of the design plant equipment. Production was initiated at Los Azufres geothermal field with wellhead generators not only to obtain electric energy at a relatively early date, but also to acquire needed information about the resource so that plans for large central power plants could be finalized. Commercial electric energy production started at Los Azufres during the summer of 1982 with five 5-MWe wellhead turbine-generator units. The wells associated with these units had undergone extensive testing and have since been essentially in constant production. The Los Azufres geothermal reservoir is a complex structural and thermodynamic system, intersected by at least 4 major parallel faults and producing geothermal fluids from almost all water to all steam. The five wellhead generators are associated with wells of about 30%, 60%, and 100% steam fraction. A study to compile existing data on the chemical and reservoir conditions during the first two years of operation has been completed. Data have been compiled on mean values of wellhead and separator pressures, steam and liquid flowrates, steam fraction, enthalpy, and pertinent chemical components. The compilation serves both as a database of conditions during the start-up period and as an initial point to observe changes with continued and increased production. Current plans are to add additional wellhead generators in about two years followed by central power plants when the data have been sufficiently evaluated for optimum plant design. During the next two years, the data acquired at the five 5-MWe wellhead generator units can be compared to this database to observe any significant changes in reservoir behavior at ...
Date: January 22, 1985
Creator: Kruger, P.; Semprini, L.; Verma, S.; Barragan, R.; Molinar, R.; Aragon, A. et al.
Partner: UNT Libraries Government Documents Department

AN INVESTIGATION OF WELLBORE SCALING AT THE MIRAVALLES GEOTHERMAL FIELD, COSTA RICA

Description: Miravalles geothermal field lies in the Guanacaste province of Costa Rica in Central America. At the time of the study (late 1982), three wells (named PGM-1, PGM-2 and PGM-3), had been drilled and periodically tested in this field during 1980-82. During several of these tests scaling of the wellbore appeared to be a serious problem. This paper presents a portion of a study conducted to define the nature and causes of the scaling problem. No new data were gathered during this study; it was based on the analysis of already existing data as of late 1982. The main limitations in the data as regards this study were: (1) no bottomhole pressure measurements had been made; (2) no temperature or pressure profile under flowing condition was available from any well; (3) a wellhead separator was available at only one well (PGM-1); and (4) although James' lip pressure measurement facilities were available at all wells, in some of the earlier tests (up to May 1981) no measurement of the liquid flow rate was made. The fact that there was scale deposition in the Miravalles wells was indicated by several observations: (1) unusually rapid decline had been experienced in both flow rate and wellhead pressure (p{sub wh}) except when the wells were flowed at a relatively high p{sub wh} level. For example, Figure 1 presents the situation for well PGM-1 during a test (Test 1). This behavior was not due to reservoir depletion because the wells produced a much larger cumulative mass without a serious drop in flow rate or p{sub wh} when flowed above a certain p{sub wh} level, whereas a much smaller cumulative production was possible if a lower p{sub wh} level was maintained. Only a part of the decline in mass flow rate in some of the tests had been ...
Date: January 22, 1985
Creator: Sanyal, S.K.; McNitt, J.R.; Klein, C.W. & Granados, E.E.
Partner: UNT Libraries Government Documents Department

Power Production from Geothermal Brine with the Rotary Separator Turbine

Description: The rotary separator turbine is a new turbine device that operates with gas-liquid mixtures. This device achieves complete gas-liquid separation, generates power from the liquid and repressurizes the liquid. The use of the rotary separator turbine for geothermal power generation was investigated on this program. A pilot scale unit was designed and tested. Tests were conducted with a clean water/steam mixture and with geothermal brine/steam flows at East Mesa, California; Raft River, Idaho; and Roosevelt Hot Springs, Utah. The test results were used to calculate the performance advantage of a rotary separator turbine power system compared to a flash steam power system and a binary power system. The calculated performance advantages were then used to estimate market potential for wellhead and central station Biphase units. The measured performance in the laboratory and in the field agreed to within {+-} 10% of the predicted values. The design goal of 20 kWe was generated both in the laboratory and from brine. Separated steam quality was measured to be greater than 99.96% at all three geothermal resources and in the laboratory. Brine pressure leaving the test unit was greater than reinjection pressure requirements. Maximum brine outlet pressure of 90 psig was demonstrated. The measured performance values would result in a 34% increase in electric power production above a single stage flash steam system. Increasing the size from the pilot size unit (20kWe) to a wellhead unit (2000 kWe) gave a calculated performance advantage of 40%. Based on these favorable results, design, construction and testing of a full-size well-head unit was initiated.
Date: December 1, 1980
Creator: Cerini, Donald J. & Hays, Lance G.
Partner: UNT Libraries Government Documents Department

Task Report Computer Program Documentation (for DEGEOWEL Well Design Program)

Description: A model has been developed that allows the design of geothermal production wells. This design problem is quite complex because of the many physical and chemical phenomena that take place in the well bore, each of which has a significant influence on the well performance with respect to total flow rate of brine and steam, pressure loss up the well, or wellhead pressure available for the power producing system, scaling and plugging of the well due to chemical precipitates. The accuracy of the design predictions were determined by comparing them with new well test data developed as part of this project. The general theory behind two-phase flow phenomena and the theory that describes the operation of the model ere described in previous reports (1, 2). This report provides a final version of the computer code, called DEGEOWEL that accomplishes the calculations according to the model. This final version incorporates the preferred correlations developed under this project for determining the flow regime, holdup and frictional pressure drop in two-phase flow. [DJE-2005]
Date: August 5, 1982
Creator: Coury, Glenn & Mickley, Michael C.
Partner: UNT Libraries Government Documents Department

Recent radon transient experiments

Description: Radon transient analysis is being developed as a method complementary to pressure transient analysis for evaluation of geothermal reservoirs. The method is based on the observations of Stoker and Kruger (1975) that radon concentration in produced geothermal fluids is related to geothermal reservoir type, production flow rates, and time. Stoker and Kruger showed that radon concentrations were markedly different in vapor-dominated and liquid-dominated systems, and varied not only among wells of different flow rate in an individual reservoir, but also varied timewise in individual wells. The potential uses of radon as an internal tracer for geothermal reservoir engineering were reviewed by Kruger, Stoker, and Umana (1977). Also included were results of the first transient test performed with rapid flow rate change in a vapor-dominated field. The results of the next four radon-flow rate transient experiments were summarized by Kruger (1978) in which effects of well interference and startup production in a new well were demonstrated. Four of these first five radon transient experiments have been carried out in vapor-dominated reservoirs at The Geysers in California and Serrazzano in Italy. The systematics of the transients of radon concentration following abrupt changes in flow rate is being evaluated by Warren and Kruger (1978). The fifth test was at the HGP-A well in Hawaii, the first transient test in a liquid-dominated reservoir. Three additional radon transient tests have been carried out, each in a different type of geothermal resource. The first test was in a petrothermal resource, the reservoir created by hydraulic fracturing by LASL in the hot, dry rock experiment in New Mexico. The results of this first 75-day production test of continuous forced circulation, during January-April, 1978, are given by Tester, et al (1978). The results of the radon concentration measurements made during this test are summarized by Kruger, Cederberg, and ...
Date: January 1, 1978
Creator: Kruger, P.; Semprini, L.; Cederberg, G. & Macias, L.
Partner: UNT Libraries Government Documents Department

Electrical Generating Capacities of Geothermal Slim Holes

Description: Theoretical calculations are presented to estimate the electrical generating capacity of the hot fluids discharged from individual geothermal wells using small wellhead generating equipment over a wide range of reservoir and operating conditions. The purpose is to appraise the possibility of employing slim holes (instead of conventional production-size wells) to power such generators for remote off-grid applications such as rural electrification in developing countries. Frequently, the generating capacity desired is less than one megawatt, and can be as low as 100 kilowatts; if slim holes can be usefully employed, overall project costs will be significantly reduced. This report presents the final results of the study. Both self-discharging wells and wells equipped with downhole pumps (either of the ''lineshaft'' or the ''submersible'' type) are examined. Several power plant designs are considered, including conventional single-flash backpressure and condensing steam turbines, binary plants, double-flash steam plants, and steam turbine/binary hybrid designs. Well inside diameters from 75 mm to 300 mm are considered; well depths vary from 300 to 1200 meters. Reservoir temperatures from 100 C to 240 C are examined, as are a variety of reservoir pressures and CO2 contents and well productivity index values.
Date: October 1, 1998
Creator: Pritchett, J. W.
Partner: UNT Libraries Government Documents Department