Due to high temperatures (approximately 320 C (608 F) BHT) and extreme abrasiveness of the deeper part of the Precambrian crystalline rocks, special problems of corrosion inhibition and of torque friction were incurred. The Precambrian crystalline portion of the EE-2 and EE-3 wells were directionally drilled at a high angle, and drilled with water as the primary circulating fluid.
Stuck pipe, repetitive reaming, poor casing cement jobs and costly damage to the intermediate casing resulted. The resultant loss of hydrostatic head caused sloughing of the Abo and of some beds within the Madera Formation. Severe loss of circulation occurred in the cavernous portions of the Sandia limestones. The drilling fluid used for the upper sedimentary formations was a polymeric flocculated bentonite drilling fluid. Beneath the Sandia Formation are igneous and metamorphic rocks more » of Precambrian age. Paleozoic strata include Permian red beds (Abo formation) and the Pennsylvanian Madera and Sandia Formations, which consist of massive limestones and shales. The Cenozoic rocks consist of volcanics (rhyolite, tuff, and pumice) and volcaniclastic sediments. Four wells (GT-2, EE-1, EE-2, and EE-3) penetrated 733 m (2405 ft) of Cenozoic and Paleozoic sediments and Precambrian crystalline rock units to +4572 m (+15,000 ft). Geothermal hot dry rock drilling activities at Fenton Hill in the Jemez Mountains of northern New Mexico encountered problems in designing drilling fluids that will reduce catastrophic lost circulation. Recent improvements in lost circulation materials and techniques and potential equipment solutions to the lost circulation problem are discussed. and coordination to library services staff in areas such as circulation. Conclusions and recommendations are presented for control of lost circulation during geothermal operations. All newly hired Los Alamos County employees are required to be fully vaccinated. Cement retarders may be needed to prevent premature setting at the higher temperatures, yet too much retarder may lead to an unsuccessful completion, particularly because of the large volume of cement that may be required to seal a lost circulation zone. High wellbore temperatures during geothermal cementing magnify the lost circulation problem. Special completion methods, such as liner and tieback string, are often used to improve cement placement and setting more » in lost circulation zones. Conventional lost circulation materials and squeeze cementing are not always successful in the cavernous and vugular low-pressure formations encountered in geothermal reservoirs. Lost circulation in geothermal wells is generally very different from lost circulation in petroleum wells. Results of this study, including interviews with geothermal production companies and with drilling fluid service companies, are reported. = ,Īssessment of the general drilling and completion practices commonly used for handling lost circulation have been surveyed and evaluated under a study sponsored by Sandia National Laboratories.
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