Research on the Calculation Method of the Technical Limit Displacement Distance Considering Variable Startup Pressure Gradient for Ultra-Low Permeability Oil Reservoirs

The reservoirs with better permeability are less affected by stress sensitivity and percolation resistance, but the ultra-low permeability reservoirs with poor reservoir quality have stronger stress, resulting in smaller pores, worse reservoir permeability and greater percolation resistance. even under the condition of dense well pattern, water injection is ineffective or ineffective. The driving distance calculation method widely used at home and abroad only considers the seepage resistance gradient of static fluid flow, and does not consider the influence of stress on displacement pressure and fluid seepage resistance. In the practical application of this method, the discrepancy between theory and practice is obtained. For this reason, the displacement pressure formula considering stress and the calculation model of variable starting pressure gradient are derived at first in our country. Based on the driving distance calculation method commonly used at home and abroad, the displacement distance calculation formula considering variable starting pressure gradient is derived. The relationship between permeability and technical limit well spacing of ultra-low permeability reservoir in Chaoyanggou oilfield is calculated. The analysis results show that compared with the traditional method, the well spacing calculated by the formula needs to further reduce the minimum driving distance of block A by 10 m to 47 m. The research results can provide a theoretical basis for the compilation of development adjustment plan for ultra-low permeability reservoirs.