Abandoned oil and gas wells : a reconnaissance study of an unconventional geothermal resource

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Reyes, A.G. 2007 Abandoned oil and gas wells : a reconnaissance study of an unconventional geothermal resource. Lower Hutt, N.Z.: GNS Science. GNS Science report 2007/23 36 p.

Abstract: There are 349 abandoned onshore oil and gas wells in New Zealand that can potentially be harnessed for geothermal energy for direct usage of heat, power production and development as pseudo hot spring systems for tourism. Well depths range from 17 to 5064m vertical. Estimated bottom hole temperatures range from ambient temperatures (about 12 to 18oC) to 172oC. Of these wells 65% are located in the North Island, the rest in South Island. Taranaki, the only oil and gas producing hydrocarbon basin in the country, has the largest number of abandoned oil and gas wells at 140 or about 40% of all onshore wells. The use of abandoned hydrocarbon wells for direct heat utilisation and power generation could add another 6.1 PJ to the geothermal energy potential of New Zealand. Of these 1.4 PJ is for use with ground source heat pumps from 123 wells with bottomhole temperatures of oC drilled to depths of 17m to 686m for space heating and heating of domestic water; 4.54 PJ for other direct heat uses from 206 wells with temperatures of 31-120oC; and 0.15 PJ from 20 wells with bottomhole temperatures of 120-172oC drilled to 3131-5064m. The total power that could be produced from the 20 high temperature wells, assuming a flow of about 4 L s-1 and a capacity factor of 10% is 4772 kWe (kilowatt electric) or an average of about 238 kWe per well. The requisite temperature may be present in abandoned hydrocarbon wells for a wide range of geothermal energy uses but there are many geoscientific, technical and non technical problems to be considered before oil and gas wells can be used for geothermal power generation or cogeneration of geothermal and hydrocarbon energy. However New Zealand has the available expertise in the geothermal and oil and gas industries and access to the requisite technology, making this scheme of converting old hydrocarbon wells for geothermal use viable. Taranaki has a large energy-intensive dairy industry that would benefit from the cogeneration of geothermal and oil and gas wells and the conversion of abandoned oil and gas wells for geothermal use. Possible sites for a 200 kWe binary cycle pilot plant have been selected, preferably using two wells, one for production and the other for reinjection of waste fluids. (auth)