Study on effects of highly deviated well on thin interbedded reservoirs fracturing

Abstract

Highly deviated well is widely applied in thin interbedded reservoirs fracturing in changqing oilfield. the oil production data shows that highly deviated fracturing well can increase the oil production compared with horizontal well fracturing, which suggests that highly deviated well fracturing is more efficient. However, it still needs deeper understanding for the mechanism of highly deviated well increase oil production, to study this problem, True-axial hydraulic fracturing physical simulation test is carried out on two kinds of cement specimen with interlayers, the results show that cement specimen for highly deviated well is more productive because fractures are more likely to cross the interbedded layers and connect oil reservoirs that separated by interlayers. Further research on the mechanism of highly deviated well fracture crossing interbedded layers is conducted via numerical simulation. Cohesive zone model is adopted to simulate the propagation of fracture in highly deviated well and horizontal well to compare the difference of thin interbedded layers stress. the results show that due to the deflection of highly deviated well fracture during propagation, the reservoir mass is divided into two parts, which causes relative displacement of rock mass on both sides of the fracture under the effect of vertical principal stress, thin interlayer eventually got broken under the action of tensile and shear stress. Both laboratory tests and numerical simulation results show that highly deviated wells have stronger interlayer penetration capability, which can improve the fracturing effect of thin interbedded reservoirs.