Abstract: In order to study the seepage characteristics of matrix and natural fracture system and its effect on productivity, We taking the typical fractured tight reservoir of Chang 3 in Wubei Oilfield as the research object, and through the nuclear magnetic resonance and the laboratory test synthesis experiment, the variation of reservoir seepage pressure gradient, the variation of matrix and fracture core pore structure with confining pressure and the variation of matrix and fracture core porosity with effective stress and stress sensitivity coefficient are determined. A multi-stage fracture horizontal well productivity model considering the initiation pressure gradient, matrix and fracture stress sensitivity differences is established and validated. The effects of starting pressure gradient, matrix and crack stress sensitivity on productivity are analyzed. The results show that the quasi-starting pressure gradient increases with the decrease of core fluidity; the porosity stress sensitivity and permeability sensitivity of fracture core are stronger than that of matrix core; the stress sensitivity of matrix has a more significant effect on productivity. Therefore, the effect of decreasing stress sensitivity and starting pressure gradient should be considered in the effective development of Chang-3 fractured tight reservoir in Weibei Oilfield.

Key words: fractured tight reservoir, seepage characteristics, starting pressure gradient, stress sensitivity, capacity analysis