碳酸盐岩非均质性对水力裂缝起裂影响的有限元法研究

Studying the effect of carbonatite heterogeneity on hydraulic fracture initiation by using finite element method

非均质性碳酸盐岩水力裂缝起裂的研究大多应用解析方法,但该方法有一定的局限性,实际地层存在流体渗流时,还应该考虑流体和固体的耦合作用。考虑到碳酸盐岩岩石力学的非均质性、流体和碳酸盐岩固体变形的相互作用的耦合效应,建立了井筒周围应力场的分布,应用有限元方法研究了碳酸盐岩非均质性对水力裂缝起裂的影响。研究表明:碳酸盐岩储层介质弹性模量和泊松比的非均质性及碳酸盐岩储层渗透率对裂缝起裂的影响显著,而且由于非均质性的影响,裂缝的起裂点在近井筒附近的地层中存在多点起裂现象;在有弱夹层地层中,裂缝起裂位置与夹层的位置密切相关。研究结果对于水力压裂优化设计的进一步改进和完善具有重要的意义。

Analytic solution mainly used in fracturing initiation research for heterogeneous carbonatite has certain limitation. When fluid percolation exists in actual formation, fluid-solid coupling should be considered. Considering both the heterogeneity of rock mechanics and the coupling effect between fluid and solid deformation, stress field distribution around the borehole was established, and finite element method was used to study the hydraulic fracture initiation in heterogeneous carbonatite. It is shown that heterogeneity of elasticity modulus, poisson ratio and reservoir permeability affects fracturing initiation significantly. Meanwhile, the heterogeneity leads to multi-point fracture initiation near the wellbore. In the formation with weak interlayer, the location of fracture initiation is correlated with interlayer location. The results have a critical influence on the further improvement of optimization design of hydraulic fracturing.