The Study On Mechanism And Control Methodologies Of Water Breakthrough For Waterflood Development In The Low-permeability Reservoir

Shallow reservoirs in our country has a considerable proportion in the low permeability reservoirs and it have more reserves.But due to the production increased of shallow gas and oil reservoirs always by fracturing horizontal seam,the mechanism of filtration and water breakthrough in horizontal fractures has a big difference with vertical fractures.Current the research on the horizontal fractures is less at home and abroad,therefore the waterflood development in horizontal fractures reservoir still exist many problems and needs be further studied.This paper analyzes the mechanism of filtration in the horizontal fractures with different shapes and periods.In the early percolation period,including the radial direction flow for the fractures to the wellbore and the vertical linear flow for the matrix above and below the horizontal fractures into the fractures,In the latter part,the percolation flow is from the vertical linear flow translate to the horizontal direction flow in reservoir,And author analysis the influence on the filtration by the horizontal fractures morphology.Based on the analysis of the percolation mechanism and characteristics of horizontal fractures,author have a detailed analysis on the mechanism of water breakthrough for the waterflood development in horizontal fractures reservoir,Simulate the flow lines of injection wells and production wells,And analysis the affects on the water breakthrough by the scale fracturing of production wells or injection wells,injector-producer distance,injector-producer horizons consistency and other factors by numerical simulation method.Evaluation the adaptability of waterflood development in horizontal fractures reservoir.This paper have a detailed analysis for production performance in actual horizontal fractures reservoir with waterflood development.Get better fitting result by segmented fitting for the early and late production decreasing due to the different percolation mechanism.By comparing the late production decline period,found a layer of a seam production capacity decreasing faster than the layer of multi-seam production capacity decreasing.By contrast the variation of water cut of water breakthrough wells with vertical fractures and horizontal fractures,found horizontal fractures reservoir exists the characteristics of the water cut after water breakthrough rises rapidly and it prone to violent flooding,and analysis of the reasons from the spatial characteristics with horizontal fractures and vertical fractures.Establish the geological model with the real production data,analysis the factors of water breakthrough in horizontal fractures of the by simulation operation.Found the waterflood development for horizontal fractures reservoir should with the large scale fracturing of production wells and no fracturing of injection wells,injector-producer distance 100 m and inversed 9 point pattern.When the injection-production ratio in 1.3 to maintain the pressure and production on a well level in horizontal fractures reservoir.Due to the presence of fractures the converted production well will yield a substantial increase in the speed of the water breakthrough.