地层产生体积压裂缝网的条件分析

Analysis on forming conditions of fracture network in volume fracturing of formation

李传亮,庞彦明,周永炳,战剑飞,朱苏阳

西南石油大学石油与天然气工程学院，四川 成都 610599 中国石油大庆油田责任有限公司勘探开发研究院，黑龙江 大庆 163712 中国石油大庆油田有限责任公司，黑龙江 大庆 163002 黑龙江省陆相页岩油重点实验室，黑龙江 大庆 163712

自然产能特别低的油气藏，渗透率往往也极低，采用直井很难实现经济有效开采，通常采用水平井加多级压裂的方式进行开采。水平井增大了油气井与储层的接触面积，多级压裂增大了储层的改造体积，进而提高了油气井的产能。多级压裂可以是分段单缝压裂，也可以是体积缝网压裂（即体积压裂）。体积缝网压裂在地层中产生纵横交错的裂缝网络，对地层的改造程度远高于分段单缝压裂。为了提高压裂效果，文中研究了产生分段单缝压裂和体积缝网压裂的地质条件和施工条件。研究认为：只有物性极差的微观非均质地层才会实现体积缝网压裂，均质地层和宏观非均质地层只会实现分段单缝压裂，只有当井底压力同时高于主裂缝和分支裂缝的破裂压力时，才会实现体积缝网压裂；为了实现体积缝网压裂，需要提高压裂泵组的功率，采用低黏压裂液和大排量泵入技术；微观非均质地层压出的裂缝都是蜿蜒曲折的，而均质地层和宏观非均质地层压出的裂缝大多是直裂缝。

Oil and gas reservoirs with extremely low natural productivity have extremely low permeability. It is difficult to achieve economic and effective production with vertical wells, so horizontal wells and multistage fracturing are usually used for production. Horizontal wells increase the contact area of wells with reservoirs, and multistage fracturing increases the stimulated reservoir volume, thus improving the productivity of oil and gas wells. Multistage fracturing can be segmented single fracture fracturing or volume fracture-network fracturing. Volume fracture-network fracturing produces crisscross fracture network in the formation, and the degree of the formation reconstruction is much higher than that by segmented single fracture fracturing. In order to improve the fracturing effect, the geological and operational conditions of segmented single fracture fracturing and volume fracture-network fracturing are studied in this paper. The research shows that only micro heterogeneous formation with very poor physical properties can have volume fracture-network fracturing, while segmented single fracture fracturing will only occur in homogeneous formation and macro heterogeneous formation. Only when the bottom hole pressure is higher than the breakdown pressure of main fracture and branch fracture at the same time can volume fracture-network fracturing be realized. In order to realize volume fracture-network fracturing, it is necessary to raise the power of fracturing pump set and adopt low viscosity fracturing fluid and large displacement pumping technology. The fractures fractured in micro heterogeneous strata are sinuous, while most of the fractures fractured in homogeneous strata or macro heterogeneous strata are straight fracture.

10.6056/dkyqt202201017