水力压裂多裂缝产生机理及影响因素

Forming mechanism and influence factors of multiple-hydraulic fractures

在对某些复杂地层进行水力压裂施工时,常会遇到异常高压及脱砂现象,有时还会导致施工的失败,而多裂缝是产生这些现象的主要原因。本文从水力压裂的原理出发,采用机理剖析的方法,分析了导致多裂缝产生的主要因素。分析认为,多裂缝的格局取决于小裂缝能否顺利连接,地应力状况对裂缝的连接与起裂方位有重大影响;天然裂缝的发育程度是决定多裂缝起裂的重要因素;地层的倾斜与井眼斜度、起裂方位、射孔等对裂缝的连接起支配作用。搞清多裂缝的产生机理对水力压裂过程中预防多裂缝的产生有着重要的意义。

In hydraulic fracturing in complex reservoirs,it is common to meet extremely high fracturing pressures and the emergence of premature screen-out,or even resulting in fracturing failure.The main causation of which is multiple-fractures.According to the principle of hydraulic fracturing,a detailed analysis of forming mechanism of multiple-fractures is given.The pattern of multiple-fractures depends on the likelihood of the join-up of minor fractures on which the status of earth stress has weighty effect.The developing degree of inartificial fractures is important in multi-fracturing;formation and hole inclination,fracturing azimuth and perforation play dominant effect on fracture connection.The prevention of multiple-fractures relies on these factors,which are important to hydraulic fracturing.