Study Of The Calculation Method And Law Of Relative Permeability For Low Permeable Reservoir

Nowadays low permeable reservoirs are widely distributed,abundant,which has become the focus of the oil and gas field exploration and development at home and abroad.In the future,low permeable reservoirs will be undiscovered oil resources and the main body of the future development for a long period.Compared to high permeable reservoirs,low permeable reservoirs have great difference in the percolation characteristics,mechanism,development and production process,which mainly reflect in the extremely low permeability and the complex pore structure,non-darcy seepage process.A large number of scholars at home and abroad carry out further study on this area and have published a large number of research results,especially for the characterization of seepage equation and pore structure analysis.While the relative permeability curve is indispensable for low permeability oil and gas field development data,and the relative permeability curve are most based on the darcy formula,is not in conformity with the percolation characteristics of low permeable reservoirs.Tiny pores of the rock,start-up pressure,capillary force and differential pressure of the flow rate is nonlinear,which exist great influence on the seepage rule and the relative permeability.Currently there is no calculation method of the relative permeability curve considering the above factors.So further study on the calculation method of the relative permeability curve considering non-darcy seepage law,capillary force is of great significance to the reasonable development of such reservoirs.Based on the measurement method of the oil industry standard for the relative permeability curve,the paper put forward the relative permeability calculation method of the steady-state method considering nonlinear seepage characteristics of low permeability reservoirs.In the basis of Berkeley-Leverett displacement theory and unsteady calculation method,introducing quasi start-up pressure seepage equation,the seepage equation of two parameters,the paper develops Berkeley-Leverett displacement theory,and deduce the water cut formula,oil and water relative permeability calculation formula considering start-up pressure,capillary force and nonlinear characteristics.Based on the indoor core data of relative permeability for the low permeability reservoir,using the derived formula,the paper analyze the nonlinear characteristics,permeability and injection rate on the influence of the relative permeability curves of low permeability reservoir.