水平井水力压裂基础理论研究

【作者】 徐严波；

【导师】 赵金洲；

【作者基本信息】 西南石油学院 ， 油气田开发工程， 2004， 博士

【摘要】 水平井具有泄油面积大、单井产量高、穿透度大、储量动用程度高、避开障碍物和环境恶劣地带等优点，在石油工业的科研和实践中成了人们关注的焦点。由于世界上低渗透油田数量很多，资源相当丰富。但低渗透油藏的渗透率低、渗流阻力大、连通性差、有时水平井的单井产能也较低，满足不了经济开发的要求，为了提高单井的产量和最终的采收率，改善其开采的经济效益，所以要对水平井进行水力压裂，而且通常需要压开多条裂缝来增加油气渗流通道，提高水平井的单井产能。 但目前为止，对水平井水力压裂的理论研究还不够深入，有些领域的研究刚刚起步，有些领域的研究国内外还是一片空白，没有一套成熟的理论模型来指导水平井的水力压裂优化设计和现场施工，使得水平井水力压裂的成功率不高而且风险也比较大。本论文的研究力图解决水平井水力压裂过程中存在的部分难题，使水平井水力压裂理论得到一定程度的提高，从而更好的指导水平井水力压裂的优化设计，提高水平井水力压裂的效果和成功率。因此，本论文的研究对推动水平井水力压裂理论的发展和指导现场施工都具有很重要的指导意义和参考价值。 在前人研究的基础上，本论文对以下几个方面进行了研究： (1) 考虑压裂液与井筒壁摩擦生热和多条裂缝分流对压裂液温度的影响，利用热力学平衡原理，建立了水平井筒温度场数学模型，用“追赶法”对模型进行了求解。考虑摩擦生热影响后压裂液温度升高了，而且粘度越大压裂液的温度升高的越多。由于压裂液温度对压裂液化学性质影响很大，本论文的研究对于确定压裂液破胶时间和指导压裂液优化设计具有重要的意义。 (2) 根据弹性力学理论和断裂力学理论，建立了水平井井筒周围应力场分布的新模型以及裂缝起裂压力和起裂角的计算模型。最小水平主应力在裂缝起裂过程中起决定性作用，岩石温度降低减小了裂缝的起裂压力。本论文建立的裂缝起裂压力计算模型能够比较准确的预测裂缝起裂时地面施工泵压，对水平井水力压裂现场施工具有一定的指导意义。 (3) 从岩石力学、流体力学等基本理论出发，综合应用了连续性方程、质量守恒方程、能量守恒方程，引用了Geensma和Deklerk提出的单缝延伸时远场地应力与裂缝入口压力的关系式和裂缝的几何尺寸计算模型，建立了多条裂缝同时压裂的二维延伸模型，并用离散变量组合型法进行求解，为水平井多条裂缝同时延伸的模拟计算提供了理论依据。 (4) 根据渗流力学和势的迭加原理，综合考虑了裂缝条数、裂缝长度、缝间距、分布的对称性、裂缝方位角、导流能力对压裂水平井产能的影响，建立了考虑多条裂缝相互干扰的压裂水平井的产能计算的新模型，并给出了模型的解析解，为压后多条裂缝相互干扰的水平井产能计算提供了很好的解决方案，而且还得出了很多新的结论。摘要 本论文的研究成果，使水平井水力压裂的基础理论更加完善，能够更好的指导水平井水力压裂的优化设计和现场施工。关扭词:水平井水力压裂温度场多裂缝裂缝起裂裂缝延伸产能预测更多还原

【Abstract】 The horizontal well has many advantages: the big drainage area, the high production rate, the high penetrating capacity, the high recovery ratio, and the ability to avoid the obstacle and terrible environment etc. In recent years, with person’s continuous practice and the development of the process technique about well drilling and well completion etc, the technique for the horizontal well is developed into the focus in the research and practice of the petroleum industry. For the low permeability reservoir, the permeability is low, the filtrational resistance is strong, and the interwell communication is poor. Sometimes, the production rate for the horizontal well also can’t arrive at the standard of the economic production. Hydraulic fracturing stimulation technique for the horizontal well has been applied to increase the production rate and the final recovery efficiency. As to enlarge drainage area of oil and gas and to improve the production rate for the horizontal well, more fractures need to be fractured usually. However, there are some difficulties in the fracturing: the temperature field distribution, the proppant transport, the fracture propagation and the production prediction for the post-fracturing.At present, the study about the basic theory of the hydraulic fracturing horizontal well is not perfect, study in some fields are done just now, while others still can’t be researched at home and abroad. There is no flawless theoretical model to direct the optimization design and site operation of hydraulic fracturing horizontal well, this makes the success ratio of hydraulic fracturing horizontal well low and risk high. In order to solve some difficulties in the hydraulic fracturing for horizontal well, improve the theory of hydraulic fracturing, direct the fracture design for the horizontal well accurately, improve the success ratio and effect of the hydraulic fractured horizontal well, so the basic theory of hydraulic fractured horizontal well is studied in this paper. The study of this paper has important significance and value; it promotes the development of the basic theory of hydraulic fractured horizontal well and directs site operation.On the basis of others, following aspects are studied in this paper:(1) According to the principle of conservation of energy, established the mathematical model for the temperature field of horizontal wellbore. In this model the effect of heat proceeded by friction and fluid diverting of multiple fractures on fracturing fluid’s temperature is considered. The model is resolved with "shooting method" in this paper. Fracturing fluid’s temperature considering the frictional heat is higher than no frictional heat, and that, the longer the wellbore is and the bigger the viscosity is, the larger the temperature difference is between considering frictional heat and no considering it. This study plays asignificant role in determining the fracture fluid’s gelout time and directing the optimum design of the fracture fluid.(2) According to the theory of elastic mechanics and fracture mechanics, established the mathematical model for the stress field distribution around the horizontal well bore and the model of fracturing pressure and fracturing angle. The minimum horizontal principle stress is key in the process of fracturing; with the decrease of the rock temperature around the horizontal wellbore, the fracturing pressure decreases accordingly. It can calculate the fracture pressure accurately and provides the reliable theoretical evidence for fracturing treatment of horizontal well.(3) On the basis of rock mechanics and fluid mechanics, using the continuity equation, mass conservation equation and energy conservation equation are used, and what is more, the relational expression between far terrestrial stress and the inlet pressure of fracture when single fracture propagating offered by Geertsma and Deklerk and the model of calculating the fracture geometry is applied. Established the two-dimensional model of multiple fractures propagating simultaneously. Mixed Discrete Value Combi更多还原