Patent RU-2378493-C1 (RU)
Title: Depreservation method of oil and gas well with non-tight production casing when permafrost formations are available in section
Inventor: KRYLOV GEORGIJ VASIL EVICH
IPC: E21B43/00
Filed: 2008-09-15
Granted: 2010-01-10
Abstract: FIELD: oil and gas production. 
     SUBSTANCE: invention refers to depreservation of gas, gas-condensate and oil wells located in the area of permafrost formations generally distributed in the section and preserved with installation method of cement plugs thus leaving clay drilling fluid in well bore and with well-control equipment and casing head available on hole mouth, which have been preserved for a long time and having non-tight production casing and big colmataged area, namely to depreservation of pioneer wells. During depreservation of oil and gas well with non-tight production casing when permafrost formations are available in the section there performed is visual inspection of hole mouth and adjacent territory, cone near mouth is filled with ground, steering wheels and pressure gauges are installed on well-control equipment and casing head, well-control equipment and casing head are heated to positive temperature within 20-30°C, pressure is checked in well-control equipment and in well tubing-casing annuli, they are pressure tested with explosion-proof mixture with nitrogen content within 92-95%, well-control equipment is removed, blowout equipment with well flushing equipment system is mounted, well production casing is heated with hot saline solution with density providing backpressure on the bed and with temperature of 60-80°C to cement plug installed in well production casing above productive bed for the period of its preservation, actual location of cement plug is determined, well production casing is interval gauged and pressure tested to cement plug on saline solution considering its density, intervals and degree of leakage of well production casing is determined with geophysical methods, injection capacity is determined with pressure created in well bore and influx is determined with level recession method, plugging material or sealing composition is installed below leakage interval of insulation cement plug and pumped behind production casing through leakage interval of well production casing, leakage interval of well production casing is set up with method of adding insulation bridge with additional portion of cement grout, the well is kept for the curing period of plugging material or sealing composition behind well production casing and cement in the added part of insulation cement bridge, insulation cement bridge is drilled in leakage interval of well production casing, repeated pressure test of the well production casing is performed, there drilled is cement bridge installed in well production casing above productive bed, on saline solution, with density providing backpressure on the bed, and with temperature of 20-30°C, well production casing is flushed to the well bottom, declaying of colmataged area of productive bed is performed by installing alkaline bath with further flushing and installation of acid bath, recovering of gas dynamic coupling of the well with productive bed is performed with perforation charges of low mining effect with deep penetration and formation of channels protruding beyond the intervals of colmataged area, swabbing from productive bed is performed; at that, pressure of pressure test of production casing with saline solution on hole mouth is determined by formula. 
     EFFECT: recovering the gas dynamic coupling of the well with productive bed when restoring technical state of the well. 
     8 cl, 5 dwg