页岩气藏压裂复杂裂缝产能研究

发布时间：2019-06-20 07:39

【摘要】：页岩气在全球具有巨大的资源量和广阔开采前景,水力压裂技术是实现其商业开采的核心技术之一,产能评价方法是优化压裂设计的有效手段之一。然而页岩多尺度储渗空间中存在气体滑脱、扩散和吸附解吸等多重复杂运移机制,页岩气储层压裂裂缝形态复杂,这对准确评价页岩气压裂井产能和依靠产能评价方法优化压裂设计构成了挑战,导致页岩气藏压裂设计有效性降低。目前国内外研究关于页岩气多重运移机制和压裂复杂裂缝形态对产量的影响认识不足。为此,本文综合考虑页岩气复杂多重运移机制和压裂裂缝复杂形态,对页岩气压裂产能进行了研究,取得的主要成果如下:考虑页岩气储层复杂孔隙结构,页岩气吸附解吸、滑脱、努森扩散和表面扩散,基于分形几何理论、哈根-泊谡叶定律、朗格缪尔吸附定律等建立了页岩纳米孔隙气体多重运移机制耦合流动数学模型。在此基础上,结合达西定律推导出了全新的与孔隙结构尺寸参数密切相关的页岩表观渗透率模型,并对模型进行了数值求解,分析了多尺度页岩气体非线性流动行为特征及分形维数、表面扩散系数等对表观渗透率的影响。在表观渗透率模型的基础上,考虑页岩气复杂渗流机理,建立了页岩气藏连续性方程,推导了无限大地层和封闭边界地层实空间点源函数。考虑压裂裂缝变缝宽和渗透率非均匀分布的实际工程特征,通过对裂缝空间离散,并采用点源函数法对页岩气藏连续性方程求解,建立了平面裂缝和非平面裂缝产能模型,推导了其数值求解格式,利用计算机编程求解得到了平面裂缝流量分布,揭示了不同气体运移机制对页岩气产量的影响规律。考虑裂缝干扰,在平面裂缝产能模型的基础上建立了分段多簇压裂水平井产能模型和拉链式压裂水平井产能模型;在非平面裂缝产能模型的基础上建立了复杂裂缝直井和水平井产能模型,采用矩阵分析方法对模型进行了数值求解,开展了页岩气藏不同压裂模式、不同复杂裂缝形态下的产能研究。考虑支撑剂非均匀铺置,缝间应力干扰的影响,分析了簇间距对页岩气藏压裂井产能的影响,同时分析了改造体积、缝网参数等的影响,并对压裂优化设计给出了建议。本文研究成果可为页岩气藏压裂优化设计和高效开发提供理论指导。
[Abstract]:Shale gas has huge resources and broad exploitation prospect in the world. Hydraulic fracturing technology is one of the core technologies to realize its commercial exploitation, and productivity evaluation method is one of the effective means to optimize fracturing design. However, there are many complex migration mechanisms such as gas slippage, diffusion and adsorption and desorption in shale multi-scale storage and permeability space, and the fracture morphology of shale gas reservoir is complex, which challenges the accurate evaluation of shale gas fracturing well productivity and the optimization of fracturing design by productivity evaluation method, which leads to the reduction of the effectiveness of shale gas reservoir fracturing design. At present, there is a lack of understanding of the influence of shale gas multiple migration mechanism and fracturing complex fracture morphology on production at home and abroad. Therefore, considering the complex multiple migration mechanism of shale gas and the complex morphology of fracturing fractures, the production energy of shale gas fracturing is studied in this paper. the main results are as follows: considering the complex pore structure of shale gas reservoir, adsorption and desorption of shale gas, slippage, Nusen diffusion and surface diffusion, based on fractal geometry theory, Hagen-Poisson's law, The coupling flow model of shale nanoporous gas transport mechanism was established by Langmuir adsorption law. On this basis, a new shale apparent permeability model, which is closely related to pore structure size parameters, is derived based on Darcy's law, and the numerical solution of the model is carried out. The nonlinear flow behavior characteristics of multi-scale shale gas and the effects of fractal dimension and surface diffusion coefficient on the apparent permeability are analyzed. On the basis of apparent permeability model and considering the complex seepage mechanism of shale gas, the continuity equation of shale gas reservoir is established, and the real space point source function of infinite geodetic layer and closed boundary formation is derived. Considering the practical engineering characteristics of variable fracture width and permeability non-uniform distribution of fracturing fractures, through discretization of fracture space and solving the continuity equation of shale gas reservoir by point source function method, the productivity models of plane fractures and non-plane fractures are established, and their numerical solution schemes are derived. the flow distribution of plane fractures is obtained by computer programming, and the influence of different gas migration mechanisms on shale gas production is revealed. Considering fracture interference, the productivity model of piecewise multi-cluster fracturing horizontal well and zipper fracturing horizontal well is established on the basis of plane fracture productivity model, and the productivity model of complex fracture straight well and horizontal well is established on the basis of non-plane fracture productivity model. The model is solved by matrix analysis method, and the productivity research under different fracturing modes and different complex fracture forms of shale gas reservoir is carried out. Considering the influence of support non-uniform paving and interfracture stress interference, the influence of cluster spacing on fracturing well productivity of shale gas reservoir is analyzed, and the effects of modification volume and fracture network parameters are analyzed, and some suggestions for fracturing optimization design are given. The research results in this paper can provide theoretical guidance for fracturing optimization design and efficient development of shale gas reservoirs.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE328

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