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Geothermal development, a natural extension of oil and gas development activities, is attracting both new petroleum engineering graduates and established petroleum engineers in increasing numbers. This paper details the challenge awaiting engineers as they work to solve first-time problems and improve technology for future activities. The geothermal industry has tremendous potential for growth, and will make a significant contribution to worldwide energy supplies.
The geothermal industry in the United States is a young industry. The first geothermal power plant, a small 12-megawatt unit, began operations at The Geysers Project in 1960, using a turbine rescued from the junk yard. It took 11 years for The Geysers electrical production to climb past the 100 MN level. By 1975, however, The Geysers field had become the world's largest supplier of geothermal energy to generate electricity with 522 MW of installed generating capacity.
This success encouraged more companies to enter the industry, and, as the price of energy rose sharply, so did lease bonus prices and the number of drilling rigs active on geothermal prospects. The rapid growth of geothermal activity has created a strong demand for talented engineers and, particularly, petroleum engineers since their education particularly, petroleum engineers since their education and training are ideally suited to geothermal development. But petroleum engineers are also in demand both in the petroleum industry and also in many other industries that emphasize technical versatility.
The purpose of this paper is to meet the competition by describing the excitement, the challenge and the opportunities awaiting both young and experienced petroleum engineers in the expanding geothermal industry.
UTILIZATION OF ENGINEERS IN THE GEOTHERMAL INDUSTRY
Not too many years ago it was difficult to recruit graduating engineers to work in the geothermal industry. Neither the students nor their professors knew much about geothermal and few offers professors knew much about geothermal and few offers of employment were accepted. That has all changed.
The geothermal industry has worked hard to acquaint engineering faculty members with geothermal, and summer employment as roustabouts and engineering assistants in the industry has introduced students to geothermal.
Graduates hired just a few years ago are now imparting their enthusiasm to younger students. The result is that the geothermal industry is now attracting higher quality graduates at starting salaries comparable with oil and gas.
Stanford University has been involved in geothermal studies since 1964, and has established an excellent research program in cooperation with the Department of Energy for, "Stimulation and Reservoir Engineering of Geothermal Resources". The major areas of research are: recovery of heat under different production mechanisms using a chimney model, steam-water relative permeability determination, geothermal well test pressure transient analysis, mathematical modeling, and the use of natural internal radon in reservoir engineering studies. More than 30 graduates of the Stanford program, representing more than eight countries, program, representing more than eight countries, are engaged in the development of geothermal energy.
A decade or so ago only a handful of experienced engineers were venturing into the geothermal industry. As growth continued and "alternate energy sources" became more popular, however, the geothermal image changed dramatically. The Geysers field began to host many distinguished visitors, including President Gerald Ford, Governor Jerry Brown, VIPS from Washington, D. C., and dignitaries from all over the world.
This "exposure" led to changes.
Zhang, ZhaoFeng (CNPC Greatwall Drilling) | Njee, James M. (KENGEN) | Han, Min (CNPC Greatwall Drilling Company) | Shan, ZhengMing (CNPC Greatwall Drilling Company) | Zhan, Min (CNPC Greatwall Drilling Company) | Sun, FaSheng (CNPC Greatwall Drilling Company)
Abstract The geothermal resources of Kenyan are located in East African Great Rift Valley. The sub surface formation has high matrix compressive strength, rapidly changing and complex lithology, abrasive, fractured and high temperatures about 350 degrees Celcius. As a result, there are many challenges encountered in drilling operations including total loss of circulation, low penetration rate, high temperature damage of directional drilling steering tools and mud motors, breakdown of drilling foam structure at high temperatures, high drill string torque, loss of cement slurry and others. By integrating conventional oil and gas drilling technology, implementation of air and foam drilling technology it has been possible to solve the loss of circulation problems, improve on hole cleaning and cuttings recovery and consequently improved the penetration rates. The application of directional drilling technology has produced wells that reach a greater portion of the reservoir by intersecting more fractures increasing geothermal wells productivity. Through proper bit selection, improved hole cleaning efficiency, reduced drill string torque, the penetration rate has been improved and also reduced the total days per well. A total of fifty seven (57) geothermal wells have successfully been drilled between May 2007 and April 2012. The drilling operation has been 100% successful with the wells being 98% productive. The production has increased from 3 - 5Mwe per single well to 16 MW due to application of directional drilling and aerated drilling technology. This is an tremendous increase of over 100%. This integrated high temperature geothermal drilling technology can be implemented in the entire East African Great Rift Valley system to develop the vast geothermal resources for economic development.
Abstract: With the concern over anthropogenic climate change (i.e. man-made climate change), there is a growing awareness that we must utilize energy resources that are sustainable. The power obtained from geothermal reservoir is one such sustainable resource that has the potential to supplement our energy systems and to displace many conventional fuels. In contrast to many renewable technologies, such as wind or solar, the geothermal resource can be used 24 hours a day, 7 days a week without any harm to the environment. It is due to this reason that geothermal development, a natural extension of oil and gas development activities, is attracting both new petroleum engineering graduates and established petroleum engineers in increasing numbers. Along with the importance of geothermal energy, this paper details as to how different phases of geothermal industry like drilling, production, and reservoir utilize petroleum engineering techniques, the challenge awaiting engineers as they work to solve first- time problems and improve technology for future activities. The geothermal industry has tremendous potential for growth and will make a significant contribution to worldwide energy supplies. Introduction: The basic study from which this paper is prepared is the result of rapidly depleting petroleum reserves and the growing need throughout the world for increasing quantities of energy in all forms. Quite obviously, natural forms of energy that are readily available at low development cost are those in greatest demand. The underdeveloped countries and particularly those having little or no petroleum resources, are the countries in which the most interest is being shown in the newer energy sources. One of the least expensive energy sources is natural geothermal energy. Although this form of energy has been recognized for centuries, it has been only during the past few decades that serious efforts have been made to harness it. Geothermal energy is heat energy originating deep in the earth's molten interior. It is this heat energy that is responsible for tectonic plates, volcanoes and earthquakes. The origin of this heat is from primordial heat (heat generated during the Earth's formation) and heat generated from the decay of radioactive isotopes. The temperature in the earth's interior is as high as 7000°C, decreasing to 650 - 1200°C at depths of 80 km -100 km. Through the deep circulation of groundwater and the intrusion of molten magma into the earth's crust, to depths of only 1 km-5 km, heat is brought closer to the earth's surface. The hot molten rock heats the surrounding groundwater, which is forced to the surface in certain areas in the form of hot steam or water (e.g. hot springs and geysers). The heat energy close to, or at the earth's surface can be utilised as a source of energy, namely geothermal energy. The total geothermal resource is vast. However, geothermal energy can only be utilised in regions where it is suitably concentrated. These regions correspond to areas of earthquake and volcanic activity, which occur at the junctions of the tectonic plates that make up the earth's crust. It is at these junctions that heat energy is conducted most rapidly from the earth's interior to the surface, often manifesting itself as hot springs or geysers. There is currently an estimated 15,000 MW of direct use and over 9,000 MW of generating capacity in geothermal resources worldwide. To put geothermal generation into perspective, this generating capacity is about 0.4% of the world total installed generating capacity.
1.0 BACKGROUND AND SUMMARY
Beginning in January, 1975, deep drilling for geothermal water began in the Raft River Valley of south-central Idaho, 6 miles north of the Utah border. The Valley has tectonic features characteristic of both the Snake River Plain volcanic rift zones, with which it intersects, and the older sedimentary characteristics of the Salt Lake - Old Lake Bonneville formations. The Valley had a number of wells showing minor thermal anomalies, and two wells producing boiling water from depths of 400 ft, evidently drilled into faults along the west edge of the Valley near the Raft River Narrows region. All of these wells were originally drilled for agricultural irrigation purposes. The geochemistry of the wells predicts maximum reservoir temperatures of 140 to 150°C (284 to 302°F), too low to compete in the electric generating market using current practiced technology for converting heat to electricity. The Idaho National Engineering Laboratory (INEL, a laboratory of the Energy Research and Development Administration) selected the area for a potential location to develop advanced technology to, hopefully, make such moderate temperature geothermal fluids more competitive in the electric generating and industrial direct heat use markets, The electric utility serving the area, the Raft River Rural Electric Cooperative, had interest in developing indigenous power sources for the future, and had a wide service territory (10,000 square miles in Idaho, Northwest Utah, and Northeast Nevada) which might well encompass other similar geothermal regions. By the fall of 1974, the U.S. Geological Survey had completed an extensive set of geophysical measurements, They and INEL assessed the geothermal potential as not being outstanding, but being typical of a western valley setting. It was found that the formation might be tighter than average, however. The electrical resistivity had identified low resistivity regions at depth, and structural interpretations had been made through the active seismic and surface geological work. The Colorado School of Mines had conducted a four month microseismic survey. The region was extremely quiescent, with no correlated events greater than +.2 on the Ricster scale during float period. The average characteristics of the Valley made it more pertinent as the site for research and development work, since experience gained from it would be transferable to many other equivalent sites throughout the west. Therefore, spurred by an initial input of drilling funds from the State of Idaho, plans were initiated to begin drilling in January 1975, into an indicated low resistivity zone at depth, approximately 12 miles due south of Malta, Idaho, 4 miles West of Bridge. (Figure 1) The shortage of drill rigs (then was the peak of the post Arab Oil embargo drilling activity in the U.S.), the INEL engaged a sister facility, the Nevada Test Site, to do the drilling.
FIGURE 1 (available in full paper)
To date, three wells have been drilled, the most recent completed in June, 1976. All have produced water from a reservoir(s) at measured temperatures of 148 to 149°C, as predicted by geochemistry. Artesian flows have been in the range of 600 gallons per minute (38 liters/sec) or higher. Artesian well head pressures are typically 10 to 11 atmospheres with a hot water column, 7 or 8 atmospheres with a cool equilibrium water column.
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The general types of geothermal systems will be defined and the appropriate rock, fluid, pressure and temperature conditions characterizing each type of geothermal reservoir will be identified. These characteristics will be related to the drilling and production problems which are encountered and the present state of the art of pertaining to the solution of these problems. Introduction The population explosion coupled with man's accelerating desire for a higher standard of living has greatly increased his demand for energy in the past, and there is evidence to expect a similar—if nor greater— demand in the future. Quite obviously, natural forms of energy that are readily available at low development cost are those in greatest demand. One of the least expensive energy sources is natural geothermal steam. Although this form of energy has been recognized for centuries, it has been only during the past 20 years that serious efforts have been made to harness it. Natural geothermal steam is now being produced through wells to drive turbines and generate electricity. Identification of geopressured resources has stimulated multiple use development in producing electrical energy, desalinated water, minerals, dissolved gases, etc. The present energy crisis in the U.S. has further accelerated interest in this potential form of energy. Recent development of the Nation's geothermal resources has focused attention on reservoir evaluation and drilling and fluid production problems. It is the purpose of this paper to problems. It is the purpose of this paper to identify these problems and success in their solution, thus far. RESERVOIR CHARACTERISTICS Although geothermal reservoir geology has not been satisfactorily described, it is generally agreed that the geothermal fluid is contained in the porous and permeable matrix rock comprising a structural trap having an impervious cap. The geothermal fluid may exist in the reservoir in the vapor, vaporliquid, or liquid state depending upon the pressure, temperature and fluid composition. pressure, temperature and fluid composition. The matrix rock may be of either the isotropic (intergranular) or fracture type or a combination of the two types.