GEOTHERMAL & GEOPRESSURE BLOWOUT CONTROL Phase I:Study of Existing Technology Phase II:Program Plan for Geothermal & Geopressure Blowout Control

摘要

At present the formation pressures in geothermal fields are generally sub-normal, or less than the pressure that wou1 d be exerted by a column of cold water from the reservoir to the surface. The temperatures encountered have been moderate and on 1y in a few instances have the surface circulating temperatures of the drilling fluid exceeded boiling. Steam wells have higher surface temperatures, but compensated with much lower pressures.nThe net result is that the pressures and temperatures that would have or could have caused serious blowouts have not been drilled and geothermal drilling has been spared a major blowout.nThe condition of moderate temperatures and 1ow pressures is already being changed and this will inevitably lead to a situation where blowouts could occur.nFortunate1y, the drilling guidelines already exist that will provide a framework for reasonable assurance that wells wi11 be kept under control. These guidelines are presented in USGS Geothermal Drilling Regulations, State of California Geothermal Drilling Regulations, and USGS Offshore Continental Shelf Drilling Regulations.nThe problem of suitable equipment is not as clear as the drilling guidelines. Investigative and developmenta1 work needs to be undertaken to assure that the well control equipment w î1 1 function in the very hot environment of high-temperature geothermal wells and worst-case conditions. The final step in worst-case conditions is a remotely operated drilling rig that will allow the crew to handle very hot pipe and fluids from a safe distance.nThe hazards of geothermal drilling are relatively moderate, and while it is possible to postulate major blowout from a worst-case analysis, the pressures, temperatures, and gasses have not yet been encountered that would make this a reasonable supposition. Continued geothermal drilling may lead into these hazardous areas and steps should be taken now to obtain the equipment and techniques needed to handle the extreme temperatures that may occur .