Numerical Simulation Study On Streamline Development Of Low Permeability Sandstone Reservoir

Low permeability sandstone reservoirs are widely distributed in China. Its low pressure,low porosity and permeability and heterogeneity, make an unclear understanding of reservoir fluid flow path and the relationship between injection and production in the development process. Consequently imperfect injection wells network, and poor oil recovery. Streamline method can not only reduce the impact of simulation grid direction and allow us to better recognize the underground migration of fluid and distribution characteristics,to better study the distribution of the remaining oil to provide a strong basis of effective water injection and programs adjustment.Based on the investigation of large numbers of domestic and foreign literature, in-depth research on streamline simulation is conducted. A mathematical model considering pressure threshold, gravity and capillary force in water flooding of low permeability sandstone reservoir is built,and the solving process of streamline method is analyzed. A homogeneous and heterogeneous model is established. Impaction of the well pattern, injection-production ratio, well spacing,pressure threshold and reservoir heterogeneity on streamline distribution and flooding efficiency are analyzed. A geological model of the Y block in QiLicun oilfield is built and numerical simulation is conducted. Analysis of reduced oil distribution is made. Streamline method is used to analyze effective network and optimize scheme.This paper mainly achieved the following understanding:(1)Streamline method can turn3D simulation problems into1D problems. Calculation is accelerated. Streamline can provide precise description of flow path in porous media, and significantly reduce impaction of grid direction.(2)Analyze the main factors that impact low permeability reservoir deve-lopment and streamline distribution:①In vertical wells networks,anti-9point network has the best recovery and highest water-cut, while five-point method is the lowest. Because the mixed five well pattern has the same spacing between injection and production wells, it has better developing efficiency than seven-point and mixed anti-9point network.②Recovery and water-cut increase with injection ration and well spacing increase compared with the injection wells to reduce the spacing, so there is a best injection ratio and well spacing. The greater the pressure threshold, the sparser the streamline distribution and the worse the recovery in anti-nine point well network.③When high permeability zone pass through line between injection and production wells, it has the most influence on recovery. ④Water-cut increases with heterogeneity in anti-nine point network.(3)Chang6is the main oil pay in Y block. It’s shallowly buried and formation pressure depletion seriously. It has poor physical properties, and is a low permeability lithological reservoir. Remaining oil analysis results show that remaining oil distribution mainly in Chang61and Chang62.(4)Flooding scheme of Y oilfield is optimized. It’s concluded that double injection volume and production rate is the best scheme.16.37%of FOIP can be recovered by the end of20years, and an increase of2.09%in recovery is obtained.