METHOD FOR OPENING OF PRODUCTIVE GAS-BEARING BED BY DRILLING Russian patent published in 2000 - IPC

FIELD: mining industry. SUBSTANCE: method relates to drilling gas wells with regulated hydrostatic pressure in bore-hole and it can be used in opening of high-capacity beds with abnormally high bed pressure. According to method, at initial moment of bed opening, calculated in compliance with formula is minimal density of drilling fluid. Opening is performed with drilling fluid ensuring minimal calculated density. Before start of drilling, determined is hydraulic pressure loss in circular space, and created is initial mouth pressure after mechanical sealing of mouth. First interval of productive bed is drilled under constant watching of pressure value in pipes during defined checking period. Depression on bed is created in case of permanent value of pressure in pipes in process of drilling subsequent intervals during defined checking period for first interval by regular reduction of mouth pressure. If pressure in pipes is reduced, process of sinking and washing well is discontinued. Well is closed and according to value of pressure in pipes determined is actual bed pressure. After that, minimal density of drilling fluid is corrected by using for example barite. Washing of well is restarted at former productive capacity of pumps, and gas cut drilling fluid is washed out. Washing-out process is carried out with maintaining permanent pressure in pipes at which no gas enters well. For opening of remaining part of productive bed, depression at top is brought to safety level by creating mouth pressure. Value of mouth pressure is determined according to formula. Pressure in pipes is measured and value of this pressure is maintained during subsequent drilling down to bed floor by controlling mouth pressure. Application of aforesaid method ensures safety and high quality of opening at depression on productive bed in conditions of abnormally high bed pressure. EFFECT: higher efficiency. 2 dwg