The Stimulation Mechanism Of The Reservoir With Low Permeability By Advancing Water Injection

Advancing water injection refers to the flood-production method in which injectors begin to flood before producers begin to put into production, and the oil saturation within the drainage area should be no less than the original oil sation when producers are brought into production, and the formation pressure are higher than the original formation pressure, and an effective flooding system is built.In view of the current situation that there is no analysis and study of the factors which affect advancing water injection within reservoirs with low permeability at home now,and the fact that there are a lot of factors to be considered to conduct the research,in addition,these factors interact each other,this paper adopts the orthogonal experiment method.Wehave studied the effect of many single factors,including well patterns,the distance of wells,the time of water injection,permeabilities, the viscocity of crude oil and the gradient of threshold pressure,to advancing water injectionwithin reservoirs with low permeability.We draw the following conclusionsThe effect of advancing water injection gets worse with the increasing well distance. When the well distance between injectors and producers is between 200 metres and 300 metres,advancing water injection is suitable.Generally speaking,five-spotpatterns are superior to inverted nine-spot patterns.The effect of advancing water injection is better when the time is ahead of 3 to 6 months.We recommend that it be 6 months.Advancing water injection is more suitable for the formation with its permeability ranging between 1×10-3μm2 to 10×10-3μm2 The effect of advancing water injection gets worse when the permeability is more than 10×10-3μm2or lower than 1×10-3μm2 The effect of advancing water injection gets worse as the formation pressure factor increases.Advancing water injection is more suitable when the formation pressure factor is less than 1 whereas the effect of advancing water injection gets worse when the factor is more than 1.The effect of advancing water injection is good when the difference between reservoir pressure and saturation pressure is between 2Mpa and 4Mpa.The viscosity of crude oil has some effect on advancing water injection.The lower the viscosity of crude oil is,the better the effect of advancing water injection is.Advancing water injection is more suitable when the viscosity is between 2 mPa·s and10 mPa·s. Advancing water injection is not suitable for the formation with high viscosity. The effect of advancing water injection is best when the pressure sensitivity is around 40%.However the effect of advancing water injection gets worse when the pressure sensitivity is too high or too low.There exists a gradient of threshold pressure in the oil field with low permeabilities and the energy of the formation depletes dramasticly.The effect of advancing water injection is good when the gradient of threshold pressure is between 0.02 MPa/m and 0.03 MPa/m.We find that the time of advancing water injection, permeabilities, well distance and the formation pressure factor are the major factors which affect the degree of reserve recovery and the oil producing capacity of each well by multiple factors range analysis.The good effect of advancing water injection can be achieved by optimizing controllable factors such as the time of advancing water injection and the well distance.