【作者】 刘世奇；

【导师】 桑树勋；

【作者基本信息】 中国矿业大学 ， 地质资源与地质工程， 2013， 博士

【摘要】 以沁水盆地南部樊庄区块煤储层地质特征、煤层气直井开发工程数据为依据，分析了樊庄区块煤层气直井产能的地质和工程影响因素，研究了它们对煤层气直井产能的协同控制作用，探索了煤层气直井产能的地质与工程协同控制机理。按照“实验—分析—理论—应用”的研究思路及“地质描述（地质模型）—物理模型—数学模型—数值模型—计算机模型—模型应用”的数值模拟方法，建立了沁水盆地南部高阶煤储层典型开发地质—工程模型、基于压裂强化改造的典型煤储层物理模型、煤储层与煤层气生产动态过程数学模型、求解数值模型和计算机模型，开发了自主知识产权的煤层气生产数值模拟软件，并实现了数值模拟软件的工程应用。本次研究取得了以下主要成果。(1)揭示了沁水盆地南部煤层气直井产能的地质与工程协同控制作用及其机理地下水流体势和煤储层渗透率控制了煤储层排水降压效果，是生产监测区煤层气直井产能的关键地质影响因素；抽采制度和水力压裂是煤层气直井产能的关键工程控制因素，抽采制度控制煤储层排水降压效果，而水力压裂能够改善煤储层渗透率、扩大供气面积。此外，临储压力比、煤储层含气性、煤体结构、煤储层埋深、煤储层构造特征、井网布置和井网加密、钻井工艺、固井工艺等对研究区煤层气直井产能均有一定影响。富气煤岩体、生产煤储层孔裂隙系统、煤层气开发工程和煤层气产出过程之间的相互作用关系构成了沁水盆地南部煤层气直井产能的地质与工程协同控制机理的内涵。煤层气产出过程是由煤层气吸附/解吸、扩散、渗流组成的连续性过程，受控于富气煤岩体、生产煤储层孔裂隙系统和煤层气开发工程，并通过原始煤储层系统平衡的破坏反作用于三者。研究区煤层气直井产能的地质与工程协同控制过程则表达了产能的原位地质类型、开发地质类型、地质与工程协同控制类型及其决定的开发技术模式四者之间的匹配关系。原位地质类型、开发地质类型与煤层气开发工程的优化匹配关系，决定了沁水盆地南部煤层气直井产能的地质与工程协同控制类型，不同产能控制类型的煤层气井具有不同的开发技术模式和工程选择。(2)建立了基于地质与工程协同控制的煤层气直井产能预测系列模型沁水盆地南部高阶煤储层典型开发地质—工程模型包括原生地质模型、压裂强化改造的煤储层地质模型以及排采动态地质模型。原生地质模型和压裂强化改造的煤储层地质模型描述了生产煤储层孔裂隙系统的宏观结构、微观结构发育特征，结构关系特征以及生产流体的运移模式。研究区3#煤储层宏观裂隙不发育，不利于煤储层渗透性，压裂裂缝成为流体流向井筒的主要介质形态，并造成流体流动形态和流动级别的改变；显微裂隙、超显微裂是沟通不同级别孔、裂隙系统的重要桥梁，对流体流动形态的转变和流动级别的划分至关重要。煤储层渗透率的动态变化模型包括恢复型动态变化模型和持续下降动态变化模型。高收缩率煤储层或前期排采制度较为平缓的煤储层，属于恢复型动态变化模型；低收缩率煤储层或前期排采较为迅速的煤储层，属于持续下降型动态变化模型。压裂裂缝渗透率的动态变化仅有渗透率下降阶段，属于持续下降型动态变化模型。基于典型开发地质—工程模型，由Warren-Root物理模型改进所建立的以压裂强化改造为依据的典型煤储层物理模型，能更好的对发育压裂裂缝的高阶煤储层渗流机理作出解释。根据改进的Warren-Root物理模型建立的沁水盆地南部煤储层与煤层气生产动态过程数学模型，考虑了重力、粘滞力、Klinkenberg效应等的影响，并将压裂裂缝作为一种单独的介质形态加以描述，更符合煤层气开发的实际。由煤储层与生产动态过程数学模型的离散化，建立了求解数值模型和计算机模型，实现了煤层气直井产能的预测过程。(3)开发了基于基础模型的高可靠性“煤层气生产数值模拟软件”依据协同控制模型和协同控制过程模型，开发了自主知识产权的“煤层气生产数值模拟软件”，实现了单井或井网排采煤层气井产能预测与历史拟合分析、单井或井网排采煤层气井压降漏斗演化、煤储层参数反演等功能。沁水盆地南部樊庄区块3#煤储层实例井验证结果表明，该软件计算结果可靠，误差较小，能够满足煤层气井产能预测与历史拟合的需求，具有较高可靠性，同时证实了基于地质与工程协同控制机理的煤层气产能预测方法的高可行性。更多还原

【Abstract】 In the paper, geologic and engineering factors for the deliverability of CBM (coalbed methane) straight wells in Fanzhuang Block are discussed on the basis of geologicfeatures and development engineering data of CBM wells in Southern Qinshui Basin.Further, cooperative control actions of geology and engineering for the deliverabilityof CBM straight wells are studied, and cooperative control mechanisms are elaborated.Typical geology-engineering model for CBM development of Southern Qinshui Basin,typical physical model of post-fracturing coal reservoir, mathematical model for coalreservoir and dynamical CBM production process, solution numerical model andcomputer model are established following the research thought as “experiment toanalysis to theory to application” and numerical simulation method as “geologicdescription (geologic model) to physical model to mathematical model to numericalmodel to computer model to model application”. Then, CBM production numericalsimulation software with proprietary intellectual property rights is developed forengineering application. The main research achievements are concluded as follows.(1) Cooperative control actions and mechanisms of geology and engineering forthe deliverability of CBM straight wells in Southern Qinshui Basin are exploredGround water fluid potential and permeability are key geologic factors of thedeliverability of CBM straight wells in research area that they control drainage anddepressurization effect of coal reservoir. Production system and hydraulic fracturingare key engineering factors of the deliverability of CBM wells. Production systeminfluences drainage and depressurization effect of coal reservoir and hydraulicfracturing improves coal permeability and enlarges gas supply area. In addition, ratioof critical desorption pressure to reservoir pressure, gas content, coal structure, coalbed burial depth, regional structure, pattern arrangement and well pattern thickening,drilling technology and cementing technology are also geologic or engineering factorsinfluenced the deliverability of CBM straight wells in research area.The relations of interaction among coal-rock mass with rich gas, pore-fracturesystem of procreative coal reservoir, CBM development projects and CBM outputprocess are geologic and engineering control mechanisms for the deliverability ofCBM wells in Southern Qinshui Basin. CBM output process is a continuous processthat constituted by adsorption/desorption, diffusion and infiltrating fluid of CBM.CBM output process is controlled by coal-rock mass with rich gas, pore-fracture system of procreative coal reservoir and CBM development projects, and reacts up onthem by the disruption of system balance of initial coal reservoir. The cooperativecontrol process of geology and engineering factors shows as matching relationshipamong in situ geology types, exploitation geology types, Optimization matching typesof CBM well productivity and CBM well development modes. Optimal matchingrelations between exploitation geology types and CBM development projects decidecooperative control types of geology and engineering for the deliverability of CBMstraight wells. Different Control types of the deliverability of CBM straight wells havedifferent exploration models and engineering choices.(2) Productivity prediction models for CBM straight wells are established on thebasis of cooperative control of geology and engineeringTypical geology-engineering model for CBM development of high-rank coalreservoir consists of initial geologic model of coal reservoir, geologic model ofpost-fracturing coal reservoir and geologic model of dynamical CBM well production.The initial geologic model and geologic model of post-fracturing coal reservoirdescribe development characteristics of macrostructure and microstructure, structuralrelationships and production fluid flow model of pore-fracture system of procreativecoal reservoir. Development degree of cleats of No.3coal bed in research area is notnotable that hydraulic fracture becomes the most important medium for fluid flow andchanges the flow pattern and demarcation of flow stage which are very different frominitial high-rank coal. Ultramicroscopic fissure, micro-fissure are importantpassageways connecting pores, pore and fracture, fracture and fracture, and veryimportant to transition of flow pattern and demarcation of flow stage in high-rank coal.Dynamic change model of coal bed permeability includes restorative dynamic changemodel and descending dynamic change model of coal bed permeability. Coal bedreservoir with high shrinkage or gently production system belongs to restorativedynamic change model and coal bed reservoir with low shrinkage or rapid productionsystem belongs to descending dynamic change model. Dynamic change of fracturingfracture permeability only has one phase in descending dynamic change model offracturing fracture permeability which is just a decline phase of permeability.On the basis of typical geology-engineering model for CBM development ofSouthern Qinshui Basin, typical physical model of post-fracturing coal reservoir isestablished by the modification of Warren-Root physical model. The typical physicalmodel can give a comprehensive interpretation of seepage mechanism in post fracturing high-rank coal reservoir. Based on the modified Warren-Root model,mathematical model for coal reservoir and dynamical CBM production process isestablished. Mathematical model is composed mainly of seepage flow differentialequations, auxiliary equations, initial conditions and boundary conditions. Gravity,viscous force and Klinkenberg effect are considered in mathematical model.Hydraulic fracture is treated as an individual medium in mathematical model thatmore in accordance with the reality of CBM development. By the discretization ofmathematical model for coal reservoir and dynamical CBM production,corresponding numerical model and computer model are established which meansforecasting process of the deliverability of CBM straight wells are achieved.(3)“CBM production numerical simulation software” with high reliability isdeveloped according to the foundation models“CBM production numerical simulation software” with proprietary intellectualproperty rights is developed on the basis of cooperative control model and controlprocess model. The software can be used for forecasting and matching deliverabilityof CBM straight well, demonstrating depressurization cone and achieving inversion ofcoal bed reservoir parameters. According to the results of instance verification ofCBM well in Southern Qinshui Bain, computation results of the software are reliableand calculation errors are slight.“CBM production numerical simulation software”has high reliability and can satisfy the needs of prediction and matching fordeliverability of CBM straight wells, which can prove that productivity predictionmethod of CBM wells that based on the cooperative control mechanisms of geologyand engineering factors has high availability.更多还原