Of all available EOR methods deployed in thin oil rims and gas/oil reservoirs gas intervention techniques seem the most effective 1,2,3,4,5 . The study of practicability of this method was carried out at one of West Siberia gas/oil reservoirs. Natural pressure depletion is the chosen production method for the reservoir in question. Almost 150 wells were drilled within the limits of the reservoir. The dominant production mechanisms are free flow and gas-lift. By the beginning of 2008 average reservoir pressure dropped to 13.0 MPa from the original 28.0 MPa. Decline of formation pressure well below saturation pressure (19.0 MPa) resulted in wells' shutting-in and curtailment of producing well stock. Prevailing causes of well problems are flooding and gas coning while in service. Mean water cut is 10%, GOR is 1600 CUM/MT, while oil production rate of available stock does not exceed 13 MT/D against start-up values of about 100 MT/D.A well drilled next to one of the clusters of the reservoir in question exposed overpressured B4 stratum. Gas flowrates in the well reach up to 106-166 MCUMD with wellhead pressures of 25.0 to 30.0 MPa. This fact encouraged the studies of possibility of gas/oil reservoir pressure maintenance by way of injection of high-pressure natural gas.

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