多条水力裂缝偏转延伸规律的影响因素

Propagation deflection factors of multi-fractures during hydraulic fracturing

 李宪文¹ 张矿生¹ 陈宝春¹ 周再乐² 张广清²

中国石油长庆油田分公司油气工艺研究院，陕西 西安 710021 中国石油大学（北京）石油工程学院，北京 102249）

Research Institute of Oil and Gas Technology, Changqing Oilfield Company, PetroChina, Xi′an 710021, China College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China)

 非常规油气田开发时，通常采用水平井分簇射孔分段压裂的方式，一次可以压开多条裂缝。施工过程中，新形成的裂缝延伸可能会逐渐靠近前一级所形成的裂缝，造成压裂液流道偏移，使裂缝难以有效分布开来而影响最终压裂效果。一条裂缝的存在或者延伸，对后续裂缝或者其他正在延伸的裂缝产生一定的吸引或排斥作用。文中通过有限元模拟裂缝的形成，对应力场进行了分析计算，得到了裂缝的间距和尺寸对裂缝间相互作用的影响规律。计算结果表明：当2条裂缝同步延伸时，裂缝相距越近、裂缝吸引会越强烈，反之亦然；当2条裂缝不同步延伸时，近距离时两裂缝均会偏向短裂缝那一边；新起裂的裂缝在前一级水力裂缝影响下，当二者距离较近时，前一级水力裂缝会对新裂缝产生吸引作用，当间距较远时，前一级裂缝对新裂缝产生排斥作用。通过对上述模型的计算结果分析，可以为分段压裂的多裂缝分布设计和射孔簇间距的优化设计提供指导。

 During the development of unconventional oil and gas, multi-staged fracturing for horizontal well is used to create several fractures in one stage at a time. During the stimulation operation process, the new fracture will probably connect to the other established fractures in present stage or the former stage, which leads to hydraulic fractures to spread effectively. A hydraulic fracture influences the extending direction of other fractures, causing certain attraction or repulsion effect. In this paper, finite element calculation is used to simulate the interaction of fractures with different spacing and lengths. The results show that when the two fractures are extending in the same pace, the interaction will gradually change from repulsion to attraction if the spacing of two fractures gets closer. On the other hand, when the two fractures are extending asynchronously, both fractures will curve towards the side of the shorter fracture if the spacing is relatively small compared with the fracture length. In addition, an already formed fracture will attract a newborn fracture at a short distance, but repel it at a longer distance. Based on the calculation above, guidance can be provided for optimization of fracture distributions for multi-staged fracturing treatments.

10.6056/dkyqt201701018