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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2023 Vol.24 No.1 P.56-63
Finite volume method-based numerical simulation method for hydraulic fracture initiation in rock around a perforation
Abstract: Hydraulic fracturing is a technique for increasing permeability in oil and gas resource development, grouting reinforcement in mine management, and geo-stress measurement. For the purpose of enhancing hydraulic fracturing in horizontal wells, oriented perforating methods have been developed. Fluid is injected into the rock through perforations, which increases fluid pressure within rock and decreases rock temperature. Then, the rock around the perforation is fractured. Therefore, fracture initiation pressure is intimately connected to the physical and mechanical properties, geo-stress, and temperature. Accurate prediction of fracture initiation pressure is crucial in the design and construction of hydraulic fracturing systems. Understanding the properties of the reservoir and state of stress around the wellbore is an effective method to predict fracture initiation.
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机构：1中国石油大学（华东），储运与建筑工程学院，中国青岛，266580；2中国电建集团中南勘测设计研究院有限公司，中国长沙，410014
目的：建立射孔围岩水力压裂起裂数值模型，提出基于有限体积法的射孔围岩水力压裂破裂数值模拟方法，从而得到流体压力分布和起裂压力等相关参数及其规律。
创新点：1.运用坐标转换和叠加原理，推导出考虑孔隙度演化的射孔围岩应力分布；2.提出基于有限体积法的射孔围岩水力压裂破裂数值模拟方法。
方法：1.考虑初始地应力、流体渗流和温度传热对射孔围岩的影响，运用坐标转换和叠加原理得到射孔围岩应力分布。2.考虑围岩渗透率和孔隙率的应力敏感性，采用有限容积法对所提出的方程进行解耦确定射孔围岩的流体压力和温度。3.在水力压裂射孔围岩破裂准则的基础上，提出射孔围岩水力压裂破裂数值模拟方法。
结论：1.随着射孔方位角的上升，需要更多的注入时间和更高的流体压力才能达到裂缝的起始；井壁不可渗时的起裂压力更高。2.当井壁不可渗时，流体压力在射孔前呈椭圆形分布，且流体压力从射孔到远处逐渐减少。当井壁是可渗时，流体压力的分布沿着井筒向外扩散。3.渗透率和孔隙度的应力敏感性增加了井周区域的流体压力和渗透率，导致流体流动范围更广，且起裂压力和时间都有所降低。
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DOI:
10.1631/jzus.A2200203
CLC number:
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On-line Access:
2023-01-20
Received:
2022-04-13
Revision Accepted:
2022-10-24
Crosschecked:
2023-02-01