裂缝干扰下水平井破裂点影响因素分析

Analysis of influencing factors for breakdown point in horizontal wells under fracture interference

尹建 郭建春 邓燕

YIN Jian GUO Jianchun DENG Yan

川庆钻探工程有限公司钻采工程技术研究院， 四川广汉　618300 “ 油气藏地质及开发工程”国家重点实验室，四川成都　610500

Drilling and Production Technology Research Institute of Chuanqing Drilling Corporation, CNPC, Guanghan 618300, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu 610500, China

为了解水平井分段压裂过程中先压开裂缝诱导应力干扰下后续裂缝破裂点位置的影响因素及其影响规律，指导水平井分段压裂射孔位置的选择，推导建立了非等裂缝半长、非等间距和任意裂缝倾角的水力裂缝诱导应力干扰数学模型，在此基础上形成了破裂点计算数学模型。结果表明包括裂缝条数、长度和净压力在内的先压开裂缝参数以及原始主应力状态、水平井方位角和完井方式等都会影响后续裂缝破裂压力大小，从而影响破裂点的位置，其中原始地应力、已压开裂缝条数和长度以及完井方式对破裂点位置存在较大影响，水平井方位角和已压开裂缝净压力对破裂点位置影响较小；对于原始水平主应力差较小的砂岩储层，裂缝间干扰严重会导致应力发生反转，增大后续起裂裂缝破裂压力，导致施工困难，因此应该尽量避免裂缝间干扰；对于页岩储层，目前采用的分段多簇射孔技术，段间距定为60 m 左右破裂压力更低，更易于裂缝起裂。

In order to understand the influencing factors for subsequent fracture breakdown point locations under the interference of induced stress by previously created fractures during staged fracturing in horizontal wells and their influencing law, and to guide the selection of perforation locations in staged fractured horizontal wells, the mathematical model for hydraulic fracture induced stress interference was built which had non-equal fracture half-length, non-equidistance and random fracture dip, and a mathematic model for calculation of breakdown point was established based on this. The results show that the previously created fracture parameters, including the number of fractures, their length and net pressure, and original dominant stress status azimuth of horizontal well and completion method can all affect the size of subsequent fracturing pressure, hence affecting the location of breakdown points. The original geostress, the number and length of previously created fractures and completion method pose a significant effect on the location of breakdown points, while the azimuth of horizontal well and net pressure of previously created fractures have little impact on the breakdown points. For sandstone reservoirs with small difference of original horizontal dominant stress, the severe interference between fractures may cause inversion of stress and increase the fracturing pressure of subsequently initiated fractures, causing difficulty in fracturing job. So the inter-fracture interference should be avoided as much as possible. For shale reservoirs, the staged multi-cluster perforation technique is used at present, and the fracturing pressure is even lower when the interval between stages is set at about 60 m, which helps fracture initiation.

10.13639/j.odpt.2015.02.024