Conventional waterflooding in naturally fractured reservoirs can be uneconomic due to poor oil recovery performance. A technique to improve the oil recovery performance is pressure pulsing water-flooding. The technique is cyclic and consists of alternately pressuring and depressuring the reservoir. During the pressuring phase, water is injected and forced under high pressure to flow from the fractures into the matrix. Fluids are produced from the reservoir during the depressuring phase. The reservoir pressure is allowed to drop until either the oil production rate becomes too low or the producing gas-oil ratio becomes excessive. Cycles are repeated as long as the process is economic.

This paper presents results of a simulation study to determine the important parameters which affect the success of pressure pulsing waterflooding. A dual porosity generalized compositional model was used for the simulations. The results show the success of pressure pulsing waterflooding is dependent on the interconnected fracture network, relative permeabilities and oil fluid properties. The fracture network allows injected water to move rapidly away from the wellbore throughout the reservoir system. Matrix relative permeabilities affect the amount of oil and water retained in the matrix rock during the depressuring phase. Gas collapse during the pressuring phase allows water to enter the matrix rock, and gas evolution in the depressuring phase drives oil from the matrix rock into the surrounding fractures. It is illustrated that the effectiveness of pressure pulsing waterflooding can be improved by conservation of gas in the reservoir and/or by supplemental gas injection in the pulsing cycles before water injection.

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