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水力压裂过程中纵向水力裂缝的形态研究

发表时间:2017-01-15  浏览量:1223  下载量:631
全部作者: 付大明,尚福林
作者单位: 西安交通大学航天航空学院
摘 要: 水力压裂过程中的纵向水力裂缝可能为双翼形态或单翼形态。研究从井壁最初形成的单翼缝出发,建立单翼缝有限元模型(finite element model,FEM)并分析单翼缝转变为双翼缝的条件。考虑到孔隙压力对岩石应力应变关系的影响,采用Biot多孔弹性理论作为数值计算的理论基础,以描述地下岩石的力学行为。考虑到孔隙压力对水力裂缝扩展的影响,进一步推导出水力裂缝的广义J积分计算公式。计算实例表明,广义J积分公式能够对尖端过压效应作出合理解释。单翼缝FEM的计算结果表明,当平行于井筒横截面的两个地应力的差值较小时,单翼缝和不对称的双翼缝可能出现,进而得出单翼缝在开始扩展后转变为双翼缝的临界井底压力值。
关 键 词: 固体力学;纵向水力裂缝;Biot本构关系;单翼缝;水力压裂
Title: Morphology study of longitudinal hydraulic fracture during hydraulic fracturing process
Author: FU Daming, SHANG Fuling
Organization: School of Aerospace, Xi’an Jiaotong University
Abstract: Longitudinal hydraulic fracture may be with one wing or two wings during hydraulic fracturing process. In this paper, hydraulic fracture with one wing is considered initially form after well fracture, the corresponding finite element model (FEM) model is proposed, and the condition that hydraulic fracture with one wing changes into hydraulic fractures with two wings is analyzed. Taking into account the influence of pore pressure on the stress-strain relationship of rock, we use Biot’s poroelastic theory as the theoretical basis of numerical calculation. This theory can well describe the mechanical behavior of underground rock. Be taking into account the influence of pore pressure on hydraulic fracture, the generalized J integral formula for hydraulic fracture is derived further. Numerical results show that this formula can give a reasonable interpretation for the crack-tip effect of hydraulic fracture. The FEM results show that both the hydraulic fracture with one wing and the asymmetric hydraulic fracture with two wings may emerge when the difference between the two ground stresses parallel to the cross-section of the wellbore is small. In addition, the critical bottomhole pressure for that the hydraulic fracture with one wing changes into the hydraulic fracture with two wings at the beginning of fracturing is obtained.
Key words: solid mechanics; longitudinal hydraulic fracture; Biot constitutive relation; hydraulic fracture with one wing; hydraulic fracturing
发表期数: 2017年1月第1期
引用格式: 付大明,尚福林. 水力压裂过程中纵向水力裂缝的形态研究[J]. 中国科技论文在线精品论文,2017,10(1):49-57.
 
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