致密油藏层内爆燃压裂缝网渗流及产能特征

The flow and deliverability in tight oil reservoir after explosive fracturing

利用类分形树状网络理论表征复杂的爆燃次生裂缝,考虑启动压力梯度和压敏效应影响,耦合基质非线性渗流区、爆燃次生裂缝波及范围的椭圆线性渗流区、主裂缝线性渗流区,建立了致密油藏水力裂缝层内爆燃压裂非线性渗流稳态模型。实例计算表明:对于致密油藏,爆燃压裂较常规水力压裂在提高增产效果方面具有明显优势,增产效果约为常规水力压裂的1.5倍。爆燃改造区域渗透率K_(in)与裂缝分形维数D_f成正比、与迂曲度分形维数D_t和裂缝分叉角度θ成反比。层内爆燃压裂增产效果主要受爆生裂缝距离影响,与裂缝分形维数D_f、迂曲度分形维数D_t相关性不强,因此选用能量释放率低或具多级反应速率的爆燃药剂,减小裂缝分叉角θ,增加爆生裂缝长度,扩大储层改造体积,是提高产能、优化储层改造效果的重点。

In consideration of the matrix,fracture network and main fracture coupling flow under the threshold pressure gradient and the pressure sensitive effect,on the basis of the fractal tree-like theory,a non-linear steady productivity prediction model was established for hydraulic fracture well after exploration.The computational results show that,compared with the conventional hydraulic fracturing,such a well in tight oil reservoir,getting 1.5times productivity,possesses evident superiority.The permeability in explosive zone is in proportion with pore fractal dimension Df,while inversely with tortuosity dimension Dtand bifurcation angelθ.The pore fractal dimension Dfand the tortuosity dimension Dthave little influence on stimulation ratio.Due to the main effect of the explosive fracture length on stimulation ratio,dynamites,with low energy release rate or multistage reaction rate,should be chosen to minish bifurcation angel and magnify facture volume.