METHOD OF PREVENTION OF THAW 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 of Extreme North regions located in frozen icy rocks. SUBSTANCE: operation of gas wells in permafrost zones is aggravated by thaw of permafrost rocks with 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 is cooled and directed to tubing-casing annulus. Gas small flow is returned to gas pipeline from annulus under pressure which is equal to pressure of formation gas in point of gas separation into two flows. In this case, pressure in gas pipeline before return of small cooled gas flow is reduced to value higher than value of hydraulic losses of this flow during its motion. EFFECT: minimized losses of formation energy for prevention of thaw of frozen rocks, higher economic efficiency and reliability of method. 1 dwg