METHOD OF DEVELOPING LOW PERMEABLE RESERVOIR BY PERIODIC INJECTION OF CARBON DIOXIDE GAS Russian patent published in 2017 - IPC E21B43/18 E21B7/04 

FIELD: oil and gas industry.

SUBSTANCE: in the method of developing low permeable reservoirs by periodic injection of carbon dioxide gas, wells with a horizontal end of the bore diameter of 5-7 inches are chosen, which tap the reservoir with an average absolute permeability from 0.001 mD to 2 mD, or lateral horizontal bores are drilled from vertical wells which tap the reservoir with the mentioned permeability. All wells must be production wells. In each of the wells, a pump is lowered to the central part of the horizontal bore on the main pipe string, through which product selection is carried out, after a period of operation and achievement of the condition q_f ≤ 0.5·q_f⁰ at P_sat ≤ P_b ≤ 0.3·P_f⁰, where q_f is the current fluid production rate of the well, q_f⁰ is the initial fluid production rate after the well is put into production before the appropriate cycle of selection-injection, P_b is the current bottom-hole pressure, P_f⁰ is the initial formation pressure, P_sat is the pressure of oil saturation with hydrocarbon gas, an additional pipe string is lowered to the horizontal bore, with a diameter of 1-2 inches with a filter, which length is not less than half the length of the horizontal bore. An additional pipe string is sealed above the upper boundary of the productive formation. If it is necessary, the main pipe string is changed to a string of such diameter, which makes it possible to carry out round-trip operations of each of the pipe strings separately. A working agent is pumped through the additional pipe string, carbon dioxide - CO₂ is used as the working agent, injection of CO₂ is carried out with a gradual increase in consumption from 0 to q_inj^max, where q_inj^max is the maximum consumption of CO₂ at injection pressure P_inj = (0.6-0.9) ·P_r, where P_r is a vertical rock pressure, when q_inj^max is reached, the injection is stopped and the well is left to redistribute the pressure in the reservoir for 5-50 days. After that, the well is put into production through an additional pipe string. The fluid production rate is increased gradually from 0 to (0.5-0.9) q_prod^max, where q_prod^max is the maximum fluid production rate at bottomhole pressure, equal to P_sat, the cycles of injection, waiting and selection are repeated.

EFFECT: oil recovery of low permeable carbonate reservoirs increase.

1 dwg, 1 ex