裂缝性油藏压裂井产能数值模拟模型研究与应用

Numerical simulation of fracturing naturally-fractured reservoirs

研究的裂缝性油藏渗流介质包括人工压裂裂缝和天然微裂缝、大裂缝及基质,将大裂缝与基质的物质交换在微裂缝系统中加以描述,建立了含大裂缝的多重介质渗流数学模型,研制了裂缝性油藏压裂后生产动态模拟器,结合塔里木盆地塔河奥陶系裂缝性油藏参数,综合研究了天然裂缝、人工裂缝对压裂后产能的影响。研究表明:天然裂缝渗透率是影响压裂后产能的重要因素之一;人工裂缝的导流能力随生产时间递减对压裂后产量有重大影响。压裂可能导致天然裂缝污染,应采用低伤害压裂液体系,最大限度地减小对天然裂缝的伤害;增加人工裂缝长度可以改善流体沿裂缝向井底的流动性能,但随着压裂液滤失量的增大对天然裂缝的污染会加重、加深,应确定合理的压裂施工规模以获得合理的裂缝长度,避免导致裂缝长度增加而产量下降。裂缝系统连通差、渗透率较低的油藏,实施压裂也难以获得理想的增产效果;含有大裂缝的井压后产量明显高于不含大裂缝的井,但易形成水窜,可导致油井压裂后含水上升较快。

Taking account of mass exchange between macro-fracture and matrix in the micro-fracture system, the multi-medium percolation model with macro-fractures is set up. The simulator for post-frac performance of naturally-fractured formation is developed. Using the data of Tahe fractured reservoir, the effects of natural fracture, artificial fracture and macro-fracture on post-frac productivity show that the permeability of the natural fracture is one important factor affecting post-frac productivity. The decrease of artificial fracture conductivity with time has important effects on post-frac productivity. Fracturing may lead to the damage of natural fracture. The increase of the length of artificial fracture can benefit fluid flowing to the well bottom along artificial fracture. But the increase of fluid leak off may result in serious damage of natural fracture. If the permeability of natural fracture is low with poorer-connecting, it is difficult to acquire better fracturing results. The post-frac production with macro-fracture is higher than that without macro-fracture.