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1、CopyRight 2007 Library of SouthWest Petroleum University单位代码：单位代码： 10615 西西 南南 石石 油油 大大 学学 博博 士士 学学 位位 论论 文文 论文题目：论文题目： 转向重复压裂力学机理研究转向重复压裂力学机理研究 研究生姓名研究生姓名 ： 王王 腾腾 飞飞 导师姓名导师姓名 ： 赵赵 金金 洲（教洲（教 授）授） 学科专业：学科专业： 油气田开发工程油气田开发工程 研究方向：研究方向： 采油采气工程理论与技术采油采气工程理论与技术 2007 年年 6 月月 14 日日CopyRight 2007 Library of
2、SouthWest Petroleum UniversityCopyRight 2007 Library of SouthWest Petroleum UniversityI 摘摘 要要 重复压裂是老油田或老油区进一步增产挖潜和进一步提高采收率的关键技术， 特别是转向重复压裂更是中高含水油田综合治理和增油控水的有效手段。 转向重复压裂能否实现造新缝一直是学术界和工程界争论的焦点。本文针对重复压裂应力场的分布特征、造新缝机理、新裂缝的重定向以及延伸规律等开展了系统研究，主要取得了如下的成果和认识： （1）系统研究了垂直裂缝井重复压裂前应力场的分布特征及其主要影响因素。研究表明，油井中初次人工裂缝
3、产生的诱导应力、油/水井生产/注入过程中孔隙压力和温度的变化是引起储层应力场变化的主要因素。 （2）建立了强制闭合条件下的压降分析模型，对初次裂缝几何参数与裂缝壁面净压力能够很好的解释，然后应用弹性力学理论，建立了油井初次人工裂缝的诱导应力模型，并采用半逆解法得到初次人工裂缝诱导应力场的解析解。 （3）综合应用渗流力学、岩石力学和热力学理论，建立了热流固三场耦合应力场计算模型。该模型对耦合渗流方程、耦合温度场方程采用有限差分法求解，而对岩土变形方程则采用有限元法求解，并采用显式交替求解方式将其结合起来整体求解：可以得到热流固三场耦合作用下油/水井生产/注入活动引起的应力场变化。 实现了对垂直裂
4、缝井重复压裂前由于长期生产/注入活动产生的诱导应力场的定量分析和模拟。 （4）系统研究了应力重定向的产生机制以及影响因素，建立了确定垂直裂缝井重复压裂前储层中应力方向的数学模型，分析了重复压裂井中的应力方向，并结合应力轨迹线，研究了重复压裂新裂缝起裂方位的预测方法。 （5）运用应力场分布和变化的研究成果，从应力场分布的角度，建立了重复压裂的最佳时机、重复压裂造新缝的条件以及重复压裂新裂缝缝长分布特征的数学模型。 （6）系统研究了垂直裂缝井重复压裂新裂缝延伸规律以及新裂缝缝长分布特征；建立了重复压裂新裂缝延伸的数学模型，并运用裂缝延伸的数值模拟，研究了重复压裂新裂缝的延伸轨迹。 （7）在理论推导
5、的基础上编制了初次裂缝参数解释软件和重复压裂井应力场分布计算软件，实现了重复压裂井应力场变化的定量分析。 转向重复压裂是重复压裂研究中的难点和应用价值的核心问题，也是制约重复压裂优化设计的关键。本文的研究可以为重复压裂优化设计提供一定的理论基础，用以指导重复压裂施工，提高其工艺可行性和经济可行性，对老油田综合治理、稳产增产具有较为重要的意义。 关键词： 关键词： 重复压裂 应力场 诱导应力 新裂缝 转向 轨迹 CopyRight 2007 Library of SouthWest Petroleum UniversityII Abstract Refracturing is a key way
6、 for enhancing productivity and recovery for the maturing oil field. It is also an effective means to integrated management and steady oil and control-water, especially for high water-cut oil field. For a long time, it is always an argument focus in the academe and project that whether the reorienta
7、tion and new fracture can be gained or not. Based on the stress change disciplinarian nearby the wellbore and the initial fracture, the mechanism of new fracture creation for refracturing is systematically studied in this paper, and the main achievements and understands are as follows: (1) The stres
8、s characteristics of vertical-fractured well and the factors affecting stress field is firstly studied in this paper. It is shown from this study that induced stress field resulted from the initial fracture and the variation of porosity pressure and temperature resulted from producing or injecting a
9、re the main factors resulting in the change of the stress field. (2) The forced closure considered, a three-dimensional analytical model for pressure decline is presented. This can better simulate the real formation situation, and then exact fracturing parameters can be analyzed and gained; with the
10、 theory of elasticity, a model of induced stress field is established for primary fracture and the analytic solution is achieved by semi- retro-solution method. (3) Integrating percolating mechanics and thermodynamics with rock mechanics, given the reservoir is elastic-plastic a thermal-hydrological
11、-mechanical mathematical model is abstractly presented; as solving, adopting the method of finite difference for percolating model and thermal model, the finite element method (FEM) for rock-change model, the stress field resulted from change of pore pressure and temperature by oil production or inj
12、ection is obtained. Quantitative analysis and simulation are also done for this induced stress field. (4) The mechanism of stress reorientation and the factors affecting stress reorientation are studied. The model for calculation of stress azimuth is put forward. We analyzed the stress orientation o
13、f the refracturing well and studied the opening spot, the opening azimuth and the direction of fracture propagation by the use of the stress track. (5) Using the achievements of the study of stress field, the mathematic CopyRight 2007 Library of SouthWest Petroleum UniversityIII models of the best f
14、easible time for refracturing, the conditions for new-fracture created and the mathematic model of fracture propagation for refracturing is set up. (6) The rules of fracture propagation and the characteristics of fracture length distribution in refracting of vertically-fractured well are systematica
15、lly studied. The track of new-fracture propagation is studied by numerical simulation of stress field. (7) Based on the theory derived, procedures of fracture parameters analysis and stress field calculation are worked out according to the visual principle with VB6.0, and then Quantitative analysis
16、and simulation are also done for induced stress field before refracturing. For refractuing, the mechanism of new fractures formation and its propagation rule are not only the keys, but also the cruxes restricting the optimal design for refracturing construction, the research in this paper can offer certain theory base for refracturing optimal design and a guidance to field treatment as well as enhance the technical and economical feasibility.
