【作者】 罗天雨；

【导师】 赵金洲；

【作者基本信息】 西南石油大学 ， 油气田开发工程， 2006， 博士

【摘要】 水力压裂是一种广泛应用的改造低渗储层的工艺技术。自上世纪八十年代以来，随着石油工业的发展、需要改造储层的复杂性增加，人们认识到用单一平面裂缝理论无法在理论上圆满解释一些施工参数、施工情况；多种检测手段证明地下存在多条横向上或纵向上同时延伸的裂缝，而这也是造成早期砂堵与加砂施工失败的原因；目前关于多裂缝的理论模型较少。因此，迫切需要研究多裂缝的形成机理、多裂缝同时延伸的模型等，来研究、理解多裂缝存在的利弊、多裂缝延伸的施工压力异常、多裂缝情况下的裂缝延伸形态、早期砂堵机理等，进而为多裂缝的消除提供理论上的支撑，以指导人们顺利改造低渗透、复杂储层。另一方面，也将提升人们对压裂机理的认识，促进基础理论的发展。 多裂缝理论是水力压裂理论的前沿理论，研究难度较大，面临问题很多。本文完成了以下探索研究工作，形成了一套研究多裂缝问题的思路与模型： 1、根据弹性力学、岩石力学、断裂力学、空间几何的基本原理，建立了套管射孔斜井中射孔孔眼周围两孔相交处由于应力的“二次集中”而产生的切应力的计算模型；建立了存在较小微环面情况下、较大微环面情况下套管射孔斜井的破裂压力计算模型。根据类比推理，建立了射孔孔眼内部的破裂压力模型；建立了射孔破裂后形成的裂缝对相邻射孔孔眼破裂压力影响的模型；建立了一般斜井不同方位射孔处起裂裂缝的总的转向角度的计算模型。 2、利用弹性力学、工程力学、断裂力学、有限元基本理论的相关理论，建立了三种用于计算应力强度因子的理论模型，即端部应力模型、DDM模型、位错密度模型；建立了计算转向角度的几种模型。上述模型可用于研究近井裂缝连接。 3、在普通二维压裂模型的基础上，考虑近井裂缝转向与沿程闭合应力变化，建立了二维单裂缝转向延伸的新模型，该模型解法的主要特点是以每单元的长度为准去搜索对应的延伸时间。 4、在考虑井筒流体压缩性形变的基础上，结合裂缝的延伸，建立了考虑井筒内压力升高的多个三维裂缝相继开启的新模型，主要包括井筒憋压模型、三维单裂缝转向延伸模型、井筒憋压模型，同时考虑裂缝连接模型和破裂压力模型，该模型用于压裂初期判断井底压力升高、多个裂缝相继开启的情况，模拟水力压裂过程中初期裂缝条数的变化。 5、结合井筒内压力协调的模型、多裂缝的连接模型、单个大裂缝的转向延伸模型的模拟结果，阐述了多裂缝的产生机理。 6、在考虑多裂缝的闭合应力干扰、滤失规律变化、裂缝转向、流量分流的基础上，建立了计算多条二维裂缝同时延伸的模型与多条纵向三维裂缝同时延伸的新模型，模拟了多裂缝闭合应力的干扰、滤失规律的变化对施工压力、裂缝宽度、长度的影响。 7、建立了分析不同方位起裂的转向多裂缝、同方位起裂的转向多裂缝、同方位起更多还原

【Abstract】 Hydraulic fracturing is a widely used stimulation technique in petroleum industry for enhanced hydrocarbon recovery from low permeable reservoirs. From 1980’ of the last century,along with the development of petroleum industry and the requirement to stimulate reservoirs which is more complicated,more and more people have realized that the theory of single and planar fracture can’t give satisfying explain over some complex phenomena and parameter in numerous field setting.Many direct and indirect diagnostic technologies have shown the simultaneous growth of multiple-hydraulic fractures which is the main causation of the emergence premature screen-outs with low proppant concentration and the failure in hydraulic fracturing treatments.So it is urgent to analysis the forming mechanism of multiple-hydraulic fractures and the theory of simultaneous propagation of multiple hydraulic fractures ,to understand the advantages and disadvantages and the extremely high net fracturing pressures,the extend configuration of every fracture ,the mechanism of premature screen-outs,so can we offer theoretic suggestion to minimize the simultaneous propagation of multiple hydraulic fractures to give successful stimulation on low permeable or /and complicated reservoirs. And to promote the development of hydraulic fracturing theory.The theory of multiple fractures is very hard to study which is immethoding theory. A set of theoretical models has been established through comprehensive research :1 、 According to the basic conception of elasticity mechanics and rock mechanics ,the mathematical model of shear stress root in the stress centralization around the perforations in deviated wellbores with perforations and the prediction model of hydraulic fracture initiation pressure and the location of fractures on the wellbore wall under different size of microannulus are established.Based on the principle of analogism,the estimation method of fracture initiation pressure inside the perforations is sought out. One theoretical model about the influence of a fracture on the initiation pressure of the adjacent perforations has been developed on the foundation of fracture mechanics. A formula is also be studied about the total turning angle from different local and direction in deviated wellbores.2、 For the goal to investigate the feasibility of fracture link-up ,integrating elasticity mechanics,engineering mechanics,fracure mechanics and finite element method, using the new method of displacement discontinuity in building engineering ,this paper established three theoretic models including fracture edge stress model,the Displacement Discontinuity Method(DDM) and the Dislocation Parameter Model.Several methods are also presented to calculate the turning angel at the end of fracture. To analyze the fracture geometry paramerers and to estimate the likelihood of the link-up of fractures ,a set of approach is builded up.3、 Based on the ordinary 2D mathematical model ,considering the fracture orientation and the changing of the confining stress in the near-wellbore region,the improved 2D mathematical model for fracture propagation and its detailed solution are established ,the main characteristic of which is to search corresponding prolongation time according to the length of every unit.更多还原