微观尺度下碳酸盐岩油藏裂缝干扰影响因素研究

Study on influencing factors of fracture interference in fracture-cave carbonate reservoirs at micro scale

碳酸盐岩油藏裂缝发育复杂,非均质性较强,复杂裂缝之间存在的相互干扰对开发效果有重要影响,但目前对于裂缝干扰的机理和影响因素研究较少。结合微流控实验和有限元数值模拟,研究了级差裂缝之间的干扰过程,并根据实验现象提出了量化评价指标"相对干扰系数RIF";基于Navier-Stokes方程建立了裂缝数值模型,研究了原油黏度、裂缝渗透率级差、裂缝长度对裂缝相对干扰系数RIF的影响规律。实验结果表明,裂缝间相对干扰系数RIF随流体黏度和渗透率级差的增大而增加,随裂缝长度的增加而减小,且都满足乘幂关系,其中渗透率级差的影响最明显。研究有助于认识复杂裂缝介质中的油水渗流规律,为进一步研究碳酸盐岩缝洞型油藏的出水规律提供指导。

Carbonate reservoirs have complex fracture development and strong heterogeneity,and the mutual interference between complex fractures has an important impact on the development effect.However,there are currently few studies on the mechanism and influencing factors of fracture interference.Combining microfluidic experiments and finite element numerical simulations,the interference process between differential fractures was studied,and a quantitative evaluation index“relative interference coefficient(RIF)”was proposed based on the experimental phenomena.Based on the Navier-Stokes equation,a fracture numerical model was established,and it was studied the influence of crude oil viscosity,fracture permeability gradient,and fracture length on RIF.The experimental results show that the RIF between fractures increases with the increase of fluid viscosity and permeability difference,and decreases with the increase of fracture length,and both satisfy the exponent relationship,and the influence of permeability difference is the most obvious.The research helps to understand the law of oil-water seepage in complex fractured media,and provides guidance for further study on the law of water production in carbonate fracture-cavity reservoirs.