ABANDONMENT METHOD OF OIL-AND-GAS WELL LOCATED IN WATER AREA OF SHALLOW WATER RESERVOIR Russian patent published in 2011 - IPC E21B33/13 

FIELD: oil and gas industry.

SUBSTANCE: wellhead territory is investigated and thickness of ice layer and depth of water reservoir around wellhead is determined. Freezing-out of wellhead platform is performed till necessary thickness of ice layer is obtained. Timber covering is laid and equipment is arranged on it. Well is killed, Christmas tree of well-control equipment to central gate valve is removed. On central gate valve there mounted is well washing equipment complex (WWEC). Washing pipes of small diametre are lowered through WWEC and tubing string located in the well. Thawing of well and pressure test of tubing and production strings is performed. Washing pipes are removed, WWEC and central gate valve is removed; and on housing of tube head there mounted is blowout preventing equipment (BOE). If there are leakages or bumps of tubing string, corrective work or leakage repair work is performed. If there are no leakages or bumps of tubing string, the latter is removed from well with down-hole equipment. In the space of productive formation and above it there installed is lower cement plug; well shaft is filled with process solution; in the space of conductor shoe there installed is upper cement plug. Well shaft above upper cement plug is filled with non-freezing fluid blocking the space of permafrost formations and depth of water reservoir considering the thickness of ice layer. Above layer of non-freezing fluid in the well shaft there installed is blind plug, and BOE is removed. On housing of tube head there mounted is central gate valve; above blind plug the well shaft and inner cavities of casing and tubing heads are filled with cement solution. After the waiting period of cement curing ends, side branches of casing and tubing strings and upper flange of central gate valve is sealed with blind flanges with location of three-way valve on upper blind flange so that pressure gauge can be arranged on it. Near external casing pipe on the wellhead in ice layer there cut is ice hole; on central gate valve, tubing and casing heads, external casing pipe protruding above the bottom of water reservoir, protective envelope is made, which is then lowered into ice hole to bottom of water reservoir. Bottom of water reservoir is dumped inside protective envelope with gravel and sand, inner space of protective envelope is cemented with cement solution in several stages with dumps of portions of gravel and sand between pumping of portions of cement solution. After WOC (waiting on cement) the welding work is performed to seal the edge of protective envelope, on which reference point is installed.

EFFECT: improving reliability of abandonment method of wells at reduction of capital costs.

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