水平井压裂裂缝起裂及裂缝延伸规律研究

水平井压裂可以有效提高低渗透油气藏水平井的采油速度和最终采收率,裂缝起裂和裂缝延伸规律是水平井压裂的关键问题之一.建立了水平井压裂裂缝起裂压力计算模型,通过分析求解模型可以得出:井筒方位角不同,最小水平主应力和垂直主应力对裂缝的起裂压力影响规律不同,在井筒方位角为0°时最不容易起裂,而在井筒方位角为90°时最容易起裂;对比分析了现有裂缝延伸模型,得出全三维裂缝延伸模型适合水平井压裂裂缝延伸模拟;分析了产层和盖层的应力差对裂缝缝高的影响,计算结果表明,当隔层与产层的应力差大于5MPa时,裂缝被限制在产层内.

Study on the initiation and propagation laws of the fractures in horizontal well fracturing

The fracturing of horizontal wells can effectively enhance the oil production rate and the ultimate recovery factor of low-permeability reservoirs,and the initiation and propagation of fractures is one of the most important issues in horizontal well fracturing.The mathematical model of the fracture initiation pressure is established,and according to the solution of the model,the conclusions can be drawn that if wellbore azimuth angle is different,the effects of vertical principal stress and minimum horizontal principal stress on fracture initiating pressure are different.The initiation of the fractures is the most difficult when the wellbore azimuth angle of the horizontal well is 0°,and it is the easiest when the orientation angle is 90°.According to the comparative analysis of the available fracture propagation models for hydraulic fracturing,it is shown that the 3-D hydraulic fracture propagation model is the most suitable for the simulation of the fracture propagation for horizontal well fracturing.The effect of the stress difference between pay formation and capping formation on the height of the fractures is studied,the result shows that the fractures are limited within the pay formation when the stress difference is more than 5 MPa.