煤层气产能分析及井型优化

发布时间：2018-01-11 20:05

本文关键词：煤层气产能分析及井型优化　出处：《中国石油大学(华东)》2015年硕士论文　论文类型：学位论文

【摘要】：煤层气作为一种新型优质的能源,其有效开发利用,不仅能改善我国能源结构,增加能源供给,缓解能源压力,还能够减少矿井灾害,保护大气环境。我国煤层气开采起步较晚,各项技术还不完善,煤层气产能影响因素复杂,不同的开采井型,具有各自的优点也存在各自的问题,开展煤层气产能分析与井型优化研究,以期为煤层气田开发方案的制定提供指导。煤储层孔裂隙结构复杂,本文结合煤层气产出过程中解吸、扩散、渗流理论,建立了考虑渗透率敏感性和毛细管力影响的煤层气水流动数学模型,依据有限元基本原理,对煤层气水流动数学模型压力场、饱和度场和含气量场方程进行了空间域内的有限元离散,采用差分格式,在时间域上进行了离散,最终推导得出煤层气水流动数学模型的有限元弱解积分形式。以FEPG有限元自动生成程序为平台,结合Fortran语言,编写了相应的煤层气产能分析程序,并与COMET3煤层气数值模拟软件进行对比验证,对煤层气压裂直井产能进行了单因素分析。结果表明:(1)煤层的渗透率越大、孔隙度越小、含气量越大、朗格缪尔压力越大、朗格缪尔体积越小,压裂直井前期产气量越高。(2)裂缝的存在减小了压力传递的阻力,增大了储层的降压范围,提高了煤层气的产气能力。(3)裂缝长度越长,导流能力越大,产气量越大,但并不是无限的,需要对裂缝参数进行优化。本文结合研究区煤储层特征,对压裂直井井网部署及井网密度、压裂水平井裂缝参数、多分支井分支数进行了优化,并对各种井型产能进行了对比分析。结果表明:(1)压裂直井产能随渗透率非均质性增强而减小;压裂水平井钻井方位垂直于面割理时,产能随渗透率非均质性增强而增大;多分支井产能受渗透率非均质性影响较小。(2)确定了目标区压裂直井井网形状为正方形井网,并优化了井网尺寸及裂缝参数,同时,对压裂水平井井段长度、压裂段数及裂缝参数和多分支井分支数进行了优化。(3)与压裂直井相比,多分支水平井开采煤层气产量较高,增产幅度较大,压裂水平井增产幅度较小。(4)在渗透率、含气量及厚度较小的煤层中,多分支井具有较好的适应性,在渗透率、含气量及厚度较大的煤层中,各种井型的产能较为接近。
[Abstract]:Coal bed methane (CBM) as a new type of high-quality energy, its effective development and utilization can not only improve the energy structure, increase energy supply, alleviate energy pressure, but also reduce mine disasters. Protection of atmospheric environment. China's coal-bed methane mining started late, various technologies are not perfect, coal-bed methane production capacity impact factors are complex, different mining wells, have their own advantages and have their own problems. The study of coalbed methane productivity analysis and well type optimization is carried out in order to provide guidance for the development of coalbed methane field. The pore and fissure structure of coal reservoir is complex. This paper combines the theory of desorption diffusion and percolation in the process of coalbed methane production. A mathematical model of coalbed gas and water flow considering the influence of permeability sensitivity and capillary force is established. According to the basic principle of finite element, the pressure field of the mathematical model of coal bed methane water flow is established. The equations of saturation field and gas content field are discretized by finite element method in spatial domain and discretized in time domain by difference scheme. Finally, the integral form of the finite element weak solution of the mathematical model of coalbed methane water flow is derived. The FEPG finite element automatic generation program is taken as the platform and the Fortran language is used. The corresponding program of CBM productivity analysis is compiled and compared with the COMET3 software. The single factor analysis of productivity of coalbed methane fracturing vertical well shows that the larger the permeability, the smaller the porosity, the greater the gas content, the greater the Langmuir pressure and the smaller the volume of Langmuir. The higher the gas production is in the early stage of fracturing, the longer the fracture length is. The existence of the fracture reduces the pressure transfer resistance, increases the pressure reduction range of the reservoir, and improves the gas production capacity of the coalbed gas. The greater the conductivity, the greater the gas production, but not unlimited, the need to optimize fracture parameters. This paper combined with the characteristics of coal reservoirs in the study area, the fracturing straight well pattern layout and well pattern density. Fracturing horizontal well fracture parameters and branch number of multi-branch wells are optimized, and various types of productivity are compared and analyzed. The results show that the productivity of fracturing vertical wells decreases with the increase of permeability heterogeneity. When the drilling azimuth of the fractured horizontal well is perpendicular to the surface cleavage, the productivity increases with the increase of permeability heterogeneity. The productivity of multi-branch wells is less affected by permeability heterogeneity.) the shape of straight well pattern in target area is determined as square well pattern, and the size of well pattern and fracture parameters are optimized at the same time. The length, fracturing section number, fracture parameters and branch number of fracturing horizontal wells are optimized. In the coal seam with low permeability, gas content and thickness, the multi-branch well has better adaptability, and in the coal seam with high permeability, gas content and thickness. The productivity of various well types is close.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE328;TE37

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