Oil and Gas expertise for Geothermal Exploitation: the Need for Technology Transfer

Abstract

Abstract Renewable energy is seen as the future source to meet the world's growing demand, with geothermal resources offering a constant and independent supply. Over the past century, the oil and gas sector has developed high level technologies for the exploitation of hydrocarbon reservoirs and this expertise should be directly transferrable to geothermal exploitation. In contrast to hydrocarbon developments, geothermal projects typically only become economic after decades of operation, which implies a long period of debt service before costs can be recovered from the sale of energy in the form of heat, electricity or a combination of both. Thus, the technology transfer between the petroleum and geothermal sectors has not been as efficient as initially hoped for. This paper begins with a review of the principles and uses of geothermal energy in today's sustainable energy scenario, from District Heating systems to the more recent Hot Dry Rock (HDR) concept. As exploiting HDR resources becomes more economic, the geothermal energy resources of countries like the U.S. could meet domestic demand for electricity for thousands of years. The challenges presented by HDR projects around the world are discussed, with a special focus on those aspects of geothermal exploitation that overlap with the oil and gas expertise, such as drilling and completions practices, the characterization of fluid flow through porous media and in wellbores and reservoir fracturing issues. The comparison shows how hydrocarbon exploration and production complements that of geothermal exploitation and identifies technical areas where future research efforts should be addressed to enhance the technology transfer between these energy sectors. Introduction Geothermal energy is a renewable source that becomes economically more attractive as the cost of conventional energy increases. The exploitation of geothermal resources incurs many of the technical challenges that are encountered in oil and gas exploration and production. Although the concept of technology transfer between these energy sectors is not new, there is still scope for improvement in the way this transfer is being done, with the aim to create more synergy between the two areas of technology application. In what follows, a review of conventional and frontier geothermal energy uses is presented, which highlights current and future technological needs, and shows how these overlap with the oil and gas industry. The source of geothermal heat The planet's internal heat, which was originally generated by accretion from the gravitational binding of energy, has continued to grow with the decay of naturally occurring radioactive elements. The earth's flow of heat from its interior to its surface is currently around 45 TW. The earth cools at an extremely slow rate: the mantle's temperature has decreased by 300–350°C in 3 billion years, and the core remains at approximately 4000°C. About 99% of the earth is hotter than 10000C and 99% of the remaining 1% is hotter than 1000C. Fig. 1 illustrates the trends of temperature in the earth.