Forecasting changes of the wells productive coefficients for the Bashkirian-Serpukhovian deposits in the north of the Perm region

UDK: 622.276.344(18)

Key words: oil reservoir, the well productivity coefficient, bottom-hole pressure, reservoir pressure, strain

Authors: V.V. Poplygin (Perm National Research Polytechnic University, RF, Perm), M. Wiercigroch, E.E. Pavlovskaia (University of Aberdeen, United Kingdom, Aberdeen)

Around a quarter of oil reserves of the north of Perm region are dedicated to Bashkirian-Serpukhovian carbonate sediments. In oil fields of that region there is a significant change in well flow rates over the time. The authors conducted a study to determine the main causes of flow rate change and well productivities. The paper describes the geological and physical characteristics for the Bashkirian-Serpukhovian deposits in the north of the Perm region. The results of the work of the oil wells are considered when the reservoirs are being depleted and bottom-hole pressure is reducing. With decrease of reservoir pressure of Unvinskoye oil field by 10% comparing to initial value there was a decrease in well oil rates almost twice. It is noted that as the bottom-hole pressure is lowered reaching the gas saturation pressure of the oil wells; the productivity coefficients are significantly reduced from the original values. The degree of the reduction of these coefficients in these conditions increases with the reservoir permeability. Based on this, an equation to predict changes in the oil well productivity index in the region above the gas oil saturation pressure was obtained. Then, we determined coefficients α₁ to assess the loss of productivity coefficients below the saturation pressure in the equation of V.D. Lysenko, as well as α₂ coefficients to assess the productivity coefficients growth with an increase in bottomhole pressure. The dependencies of the wells productive coefficients on the bottom-hole and reservoir pressures are obtained for the Bashkirian-Serpukhovian deposits.
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