【作者】 王文东；

【导师】 苏玉亮；

【作者基本信息】 中国石油大学(华东) ， 油气田开发工程， 2015， 博士

【摘要】 面对巨大的能源需求,非常规油气资源的战略地位日趋重要,该类储层基质孔渗差,天然裂缝非连续、非均匀及分叉特征明显,导致渗流机理比常规油气更为复杂。体积压裂以形成复杂缝网为致密油气提供流动通道为目的,已成为非常规油气增产的主要技术。但目前定量描述体积压裂缝网分布难度大,现有渗流理论和模型也已不再适用,迄今尚未建立一套体积压裂复杂裂缝网络分布表征-流动模拟系统理论和方法。本论文针对非常规油气体积压裂后储层缝网结构特征,提出考虑“有效改造体积”的复合流动双重介质模型,精确刻画了体积改造后多重渗流区域的耦合流动特征,研究了储层改造带宽对压力动态和产量变化规律的影响;其次,考虑致密多孔介质孔隙和非连续裂缝介质的多尺度性,推导了分形介质网络孔隙度、渗透率微观表达式,提出了流体在体积压裂水平井复杂非均匀双重介质中的分形反常扩散流动数学模型,揭示了基质/裂缝分形维数、反常扩散系数等分形参数对体积压裂水平井渗流规律的影响,得到了不同裂缝网络分形维数下存在的储层改造体积渗透率阈值。计算表明,裂缝分形维数越大,储层改造体积渗透率阈值也越高,改造效果也越好;第三,通过对复杂裂缝介质中人工裂缝显式处理,建立了基于缝网双重介质体系的体积压裂水平井数学模型,采用有限元数值计算格式对宏观裂缝数学模型进行数值离散和求解,得到了体积压裂水平井压力分布。该模型更为准确的描述了储层改造体积与裂缝附近流体的流动状态,明晰了典型裂缝改造模式下的流动机理,计算表明,储层改造体积、改造带宽对体积压裂产能影响较大;其次,创建了能够描述缝网微结构特征的自相似分形分叉复杂裂缝网络描述和模拟方法。借助分形分叉理论和离散裂缝方法建立了数学模型,分析了分叉缝网密度、分叉缝网模式及分形缝网导流能力对非稳态产能的影响。计算表明,分叉密度越大,油藏接触面积越大,开发效果受到末端分叉缝的干扰越大;最后,创建了基于随机分形缝网的分布模拟和反演方法。基于L-system的随机分形缝网表征和建模方法,综合考虑页岩气藏的吸附解吸规律及非稳态渗流特征,借助整数规划算法和微地震数据拟合复杂缝网的分布形态,利用遗传算法(GA)对生产数据历史进行拟合从而反演复杂分形裂缝网络模式和介质参数。本论文系统研究了体积压裂复杂裂缝网络表征方法,建立了一套体积压裂水平井复杂分形裂缝网络流动模拟理论体系,为非常规致密油气高效开发奠定了理论基础。更多还原

【Abstract】 The potential of new type of unconventional resources,“unconventional reservoir” has attracted a great deal of public interest,compare to conventional reservoirs,Compared to conventional reservoirs,fluid flow in unconventional reservoirs is driven by ultra-lowpermeability and discontinuous fractures and involves many coexisting processes due to the presence of multi-scale fracture networks.The purpose of multi-staged fracture networks is intent to provide flow pathway in ultra-tight formation,which has already become most useful technics in unconventional oil & gas stimulation.But quantifying complex fracture network in unconventional reservoirs remains a significant challenge,the existing flow mechanism and theoretical models are limited from fully representing the geometry of complex fracture networks and simulation approach.To account for the structure of complex fracture and stimulated reservoir volume,we proposed composite dual-porosity linear flow model.our model is based on four linear flow regions including the hydraulic fracture,the stimulated reservoir,the unstimulated reservoir,and the outer reservoir region,which accurately depict the coupling of multiple flow region,we perform the sensitivity studies to present the degree to which the vary as size and other properties of SRV change.Secondly,multi-scale feature is proposed to consider the ultra-tight porous media and discontinued fracture medium,fractal permeability and porosity relationship is introduced to develop fractal anomalous diffusion mathematical model.The study revealed that matrix/fracture fractal dimension、anomalous diffusion parameter have an important impact on flow mechanism in fractured horizontal well,we also stated that the presence of lower limit of stimulated reservoir threshold permeability,which is strongly influence by fracture fractal dimension.Thirdly,we develop dual-porosity based multiple fractured horizontal well model,which complex fractures and hydraulic fracture are modeled explicitly as one or more 1D,finite element method is employed to carry out a discrete solution for a macro fractures and solve for wellbore pressure.The model could precisely describe the flow behavior inside the stimulated reservoir volume or belong the hydraulic fracture,which clarify the flow characteristic with respect to the typical reservoir stimulated volume.The result show that with higher stimulated reservoir volume and fairway length,the higher well performance will have.Then,we propose new numerical method to characterize the structure of fractal bifurcate complex fracture network.Fractal theory and discrete fracture method is employed to set up the mathematical model,we also perform sensitivity studies to present the degree to which the rate transient behavior very as bifurcate fracture density,bifurcate fracture network mode and conductivity.By increasing bifurcate density,higher reservoir contact area will have,but also the well production could be decreased with bifurcate fracture network interference.Finally,we develop random fractal based fracture network geometry and inversion approach.By using L-system algorithm,we generate random fractal fracture network geometry,meanwhile,apply the integer programming algorithm and the micro-seismic data to do the fitting complex geometry of fracture network.Adsorption and desorption,transient flow behavior are considered in shale gas reservoir simulation model,then GA algorithm is applied to solve the history matching problem and invert the fracture properties.In this paper,we study the complex fracture characterization method systematically,and provide a new methodology and technology for flow simulation in multiple-fractured horizontal well.更多还原