【作者】 黄中伟；

【导师】 李根生；

【作者基本信息】 中国石油大学 ， 油气井工程， 2007， 博士

【摘要】 水力压裂技术经过了半个多世纪的发展,在缝高控制技术、高渗层防砂压裂及大砂量多级压裂等方面都取得了长足进展,但仍存在不少问题,如裂缝位置及方向难以控制、起裂压力较高、压裂裸眼段时压裂液的大量漏失(有天然裂缝时更为严重)、裸眼水平井段只在端部开裂等,这些问题增加了压裂成本、降低了压裂效果。采用水力喷射辅助压裂可望解决上述问题。本文采取了理论研究、数值模拟、室内实验和现场试验相结合的研究方法。根据岩石断裂力学、破碎力学等基础知识,分析裂缝起裂、扩展的机理;应用有限元软件,数值模拟不同射孔参数下裂缝起裂、扩展规律;制作岩样,改变岩样中孔眼参数,室内实验不同条件下的起裂压力、起裂时间、裂缝扩展形态等,并采用分形几何的有关理论,对裂缝形态进行了分析;制订现场施工工艺,设计施工参数,初步进行了现场试验,取得了显著效果。本文的研究取得以下主要成果:(1)理论分析了射孔孔眼壁面应力分布,得出了孔眼壁面裂缝起裂位置和地应力的关系;从分析应力强度因子入手,得出了岩石中微裂纹达到临界扩展状态需要满足的条件,推导了维持裂纹继续扩展的条件;(2)通过数值方法得到了孔眼参数对起裂压力的影响规律以及裂缝扩展形态;(3)室内实验得出了孔眼参数对起裂压力、起裂时间的影响规律;(4)采用分形方法分析了压裂实验后形成的裂缝面问题,计算得出了确定的分形维数,证实压裂实验的裂缝面具有明显的分形特征,对现场压裂作业中判断裂缝形态奠定了基础;(5)提出了“水力密封环”的概念,计算了水力喷射过程中地层孔眼内外的压差,制定了多种现场施工方案;(6)根据理论和实验研究结果及施工方案,进行了初步现场试验,增产效果十分显著。更多还原

【Abstract】 After developing for more than half a century, the fracturing technology has made a great progress in such aspects as fracture height control, fracturing to control sand in high penetration formation, and multi-grade fracturing with a large amount supporting sand, etc. However, there still exists the following problems: hard to control its initial position and propagation direction, higher initial pressure, liquid loss in open hole fracturing(especially with natural fractures), only initiation at the top of the horizontal open hole, etc. These will increase the fracturing cost and negate its effectiveness. Fracturing assisted with water jet will be possible to solve the above problems.This dissertation used theoretic analysis, numerical simulation, experiments and field test, to study those problems. The principles of fracture initiation and propagation was analyzed according to Fracture Mechanics of Rock and Rock Breaking Mechanics; adopted finite element method, the author simulated the law of fracture initiation and propagation; the initial pressure, initial time and the fracture shape were experimented by changing the perforation perimeters in cement samples; also, the fracture shape was analyzed using Fractal Theory; finally, on the basis of the previous results and establishing operation procedure, field test was performed and brought an obvious effectiveness.The main results include: (1) in theoretical aspect, we analyzed the stress distribution on the perforation wall, getting the relationship between the initial position and the in-situ stress; the condition of micro-fracture reaching critical propagation state and its continuing propagating were concluded from the point of analyzing the stress intensity factor; (2) the effect of perforation parameters on initial pressure and fracture shape were made through numerical method; (3) the author experimented the effect of perforation parameters on initial pressure and initial time, and the results were shown in different curves; (4) the author analyzed the fracture shape, extracted from the experiments, using fractal theory, and calculated the fractal dimensions. This proves that the fractures has the obvious fractal features, which provided guides for judging the fracture shape in field fracturing operation; (5) the author put forward a new concept of“hydro-seal”, calculated the pressure difference between the inside and outside of the perforation when blasting, and worked out several operation schemes for field test; (6) according to the above results, we conducted a field test in a well, enhancing its production remarkably after the performance.更多还原