玛湖地区致密砾岩人工裂缝垂向延伸机理应力模拟

doi:10.7657/XJPG20200209

摘要/Abstract

摘要：

针对新疆油田玛湖砾岩油藏储集层特低孔特低渗特征,开展水平井体积压裂改造储集层试验,但由于泥岩夹层多,压裂缝穿层难,压裂缝如何最大程度连通储集层是一大难点。以流固耦合和岩石弹塑性断裂力学理论为基础,以有限元数值模拟为手段,探讨水平井体积压裂过程中泥岩层的应力演化规律和破裂机理,对泥岩夹层厚度、岩石力学参数、地层倾角、有效应力等影响因素进行分析。结果表明,在一定压裂液注入速度（压裂液施工排量3.5 m ³/min）条件下,压裂缝穿越泥岩夹层有效厚度小于5.0 m;砾岩和泥岩力学参数差异越大、泥岩层地层倾角越大,压裂缝穿透泥岩的能力越差;最小水平有效主应力对裂缝垂向上的延展具有主导作用。此外,水平井距泥岩层距离以及井口注入压力对裂缝的延伸都有重要影响。施工作业时,应避免距泥岩隔夹层近距离射孔,以提升压裂效果。

关键词: 玛湖凹陷, 致密砾岩, 水平井体积压裂, 人工裂缝, 地应力, 泥岩层, 数值模拟

Abstract:

In the light of the features of ultra-low porosity and permeability of the conglomerate reservoir in Mahu oilfield, the volume fracturing tests in horizontal wells are carried out to stimulate the reservoir. However, how to connect reservoirs at the extreme through hydraulic fracturing is a major difficulty in both theory and practice. Based on the theories of fluid-structure interaction and rock elastoplastic fracture and by means of finite element method, the paper discusses the stress evolution rules and fracture mechanism of mudstone layer, and analyzes the influencing factors such as mudstone interlayer thickness, rock mechanical parameter, dip angle and effective stress during volume fracturing in horizontal wells. The study results show that if the injection rate of fracturing fluid is constant, the effective thickness of the mudstone interlayer penetrated by hydraulic fractures is less than 5 m; the larger the differences of the mechanical parameters between conglomerate and mudstone, the larger the dip angle of mudstone layer and the worse the penetrating capability of the hydraulic fractures; the minimum horizontal principle stress plays a leading role in fracture propagation vertically. Additionally, the distance from a horizontal well to mudstone layer and well injection pressure have great influences on fracture propagation. Perforation at close range to mudstone interlayers should be avoided to improve fracturing effect.

Key words: Mahu sag, tight conglomerate, horizontal well volume fracturing, artificial fracture, in-situ stress, mudstone layer, numerical simulation

中图分类号:

TE357

王硕, 覃建华, 杨新平, 李晓山, 张艺, 王英伟. 玛湖地区致密砾岩人工裂缝垂向延伸机理应力模拟[J]. 新疆石油地质, 2020, 41(2): 193-198.

WANG Shuo, QIN Jianhua, YANG Xinping, LI Xiaoshan, ZHANG Yi, WANG Yingwei. Stress Simulation of Vetical Hydraulic Fracture Propatation Mechanism in Tight Conglomorate Reseriors of Mahu Area[J]. Xinjiang Petroleum Geology, 2020, 41(2): 193-198.

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