METHOD OF THAW PREVENTION OF WELLBORE REGION IN PERMAFROST ZONE Russian patent published in 2001 - IPC

FIELD: oil and gas producing industry; applicable in installation and maintenance of equipment of gas wells in regions of Extreme North, in frozen icy rocks. SUBSTANCE: operation of gas wells in permafrost zones is aggravated by thaw of permafrost rocks and wellhead wall collapse, loss of stability of well upper casing, annulus gas showing in decomposition of hydrated gas accumulations in this zone in course of thaw of wellbore region. Method includes recovery of formation gas from well and its separation into two flows. Large flow is directed to gas pipeline. Small flow after cooling is directed to pipe-like heat exchangers-coolers located in tubing-casing annulus or in wellbore region of frozen rock mass and returned to gas pipeline under pressure equaling that of formation gas in point of its separation into two flows. In so doing, pressure in gas pipeline before return to it of small cooled gas flow is reduced to value exceeding value of hydraulic losses in this flow during its motion. Pipe-like heat exchanger-coolers may be located between surface casing and flow string or between surface casing and frozen rock mass. EFFECT: minimized losses of formation energy for prevention of thaw of frozen rocks, increased economic efficiency and reliability of offered method. 3 cl, 3 dwg