应力阴影效应对水力多裂缝起裂与扩展的数值模拟研究

发布时间：2018-06-29 12:45

本文选题：体积压裂 + 多裂缝　；参考：《东北石油大学》2017年硕士论文

【摘要】：水平井体积压裂技术是非常规页岩储层开采的重要改造措施,采用分段多簇射孔多段同时压裂工艺,先存裂缝会产生应力阴影效应,对后续裂缝的起裂与扩展造成影响,深入研究应力阴影效应的作用机制,对有效降低起裂压力,控制裂缝走向,提高体积压裂效率具有重要的意义。本文采用ABAQUS有限元仿真平台,考虑岩体的流固耦合效应,压裂时的瞬态效应,建立多裂缝起裂与扩展的力学模型及有限元模型。采用粘结单元技术模拟先存裂缝,给出应力阴影的分布规律,依据最大周向拉应力准则,计算应力阴影下后续裂缝的起裂压力及变化规律,并对现场井进行验证计算,数值分析与测试误差为5.2%,验证了数值模拟的可行性,在此基础上,分析了地应力类型、初始地应力差、到裂缝距离、排量、缝高、弹性模量以及泊松比对多裂缝起裂压力的影响规律,计算结果表明:应力阴影效应下,正断层水平井多裂缝起裂压力受初始地应力差、排量、缝高、弹性模量以及泊松比的影响而增大。逆断层水平井多裂缝起裂压力受排量、弹性模量以及泊松比的影响而增大,随初始地应力差的增大呈减小趋势,当初始地应力差大于4.8MPa时,应力阴影可以促进起裂。采用三维扩展有限元技术,建立水平井多裂缝延伸的扩展有限元模型,在射孔眼处不断注入压裂液,并对多裂缝的扩展形态进行动态追踪,得到水平井多裂缝条件下多裂缝相互影响和扩展形态。数值模拟结果表明:多裂缝扩展形态受裂缝距离、初始地应力差、排量影响较大,受弹性模量影响较小,多裂缝扩展呈现相互排斥的现象。当水平地应力差相差不大时,可以激活新的裂缝。上述研究成果为应力阴影效应在致密或非常规储层中的应用提供了理论依据,对实际生产具有一定的指导意义。
[Abstract]:The horizontal well volume fracturing technique is an important transformation measure of the unconventional shale reservoir mining, using the multi section multi cluster perforation and multi section fracturing technology, the stress shadow effect will be produced by the crack first, which will affect the crack initiation and expansion of the subsequent cracks, and the mechanism of the stress shadow effect is deeply studied, and the cracking pressure is effectively reduced and the crack control is controlled. In this paper, the ABAQUS finite element simulation platform is adopted to consider the fluid solid coupling effect of the rock mass and the transient effect of the rock mass, the mechanics model and the finite element model of the multiple crack initiation and expansion are established. The distribution law of stress shadow is given by using the bonding element technique to simulate the distribution of the stress shadow. According to the maximum circumferential tensile stress criterion, the cracking pressure and change law of the subsequent cracks under stress shadow are calculated, and the field well is verified and calculated. The numerical analysis and test error are 5.2%, which verifies the feasibility of the numerical simulation. On this basis, the stress type, the initial stress difference, the crack distance, the displacement, the seam height, the elastic modulus are analyzed. The results show that under the effect of stress shadow, the pressure of multiple cracks in the horizontal well of the normal fault is affected by the initial stress difference, the displacement, the height, the modulus of elasticity and the Poisson's ratio. The pressure of multiple cracks in the horizontal well of the reverse fault is affected by the displacement, modulus of elasticity and Poisson's ratio. The influence increases with the increase of the initial stress difference. When the initial stress difference is more than 4.8MPa, the stress shadow can promote the cracking. The extended finite element model of multi crack extension in horizontal well is established by using the three-dimensional extended finite element technique, and the fracturing fluid is constantly injected into the perforation eye, and the expansion form of multiple cracks is dynamic. The results of numerical simulation show that the expansion morphology of multiple cracks is affected by the distance of the cracks, the initial ground stress is poor, the displacement is greatly influenced, the modulus of elasticity is less affected and the multiple crack propagation is mutually exclusive, and it can be activated when the difference of the horizontal stress difference is not large The above research results provide a theoretical basis for the application of stress shadow effect in dense or unconventional reservoirs, and has a certain guiding significance for practical production.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE357.1

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