Abstract: When horizontal well group develop tight oil reservoirs, the decrease of pore pressure will significantly change the distribution of interwell geostress. So the fractures in infill wells tend to propagate toward the depleted region, and the production of infill wells is limited. Therefore, the spatio-temporal evolution characteristics of interwell stress field in tight oil reservoirs is an important basis for well layout and fracturing optimization. Based on the porous elastic theory and the development parameters of typical tight oil reservoirs, a stress-seepage coupling model was built to find out the dynamic variation of the geostress field between horizontal wells with the decrease of pore pressure. Taking the change of pore pressure as the evaluation index when the horizontal principal stress direction inverse, carry out the effect of reservoir physical property and fracturing completion parameters on the spatial-temporal evolution of geostress. Results show that the direction of the maximum horizontal principal stress between wells changes with the decrease of pore pressure; the horizontal principal stress inversion is accelerated by the decrease of reservoir matrix permeability or well spacing or the increase of daily production per well or pressure fracture spacing. The initial pore pressure has no influence on the variation trend of horizontal principal stress, and the main factor is well spacing.

Key words: tight oil reservoir, hydraulic fracturing, fluid flow, pore pressure, geostress field