页岩气藏压裂水平井压力及产量动态特征研究

发布时间：2018-02-27 22:21

本文关键词： 页岩气藏非稳态水平井多级压裂压力动态产量递减　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：作为非常规能源的页岩气因其巨大的地质储量受到了全球的广泛关注,也使得我国对页岩气藏的勘探开发工作日渐重视。页岩气藏独特的储层特征、气体赋存状态特征以及储层中气体的微观运移特征导致其与常规气藏有着很明显的不同,其中包括页岩储层为特低孔、特低渗的致密储层,页岩气藏中的甲烷同时以吸附态和游离态的方式赋存,储层中气体的渗流方式包含扩散渗流以及达西渗流。目前对于页岩气井的压力动态分析和产量动态分析大多是基于常规双重介质建立的,通常在气藏渗流模型中忽略了吸附扩散项。本文基于页岩气藏的储层特征、气体赋存状态特征以及页岩气微观运移特征,建立了双重介质页岩气藏非稳态渗流数学模型,并应用Laplace变换、点源函数等相应数学方法得到了连续点源解,并在此基础上分别建立了垂向顶底封闭、水平向无限大条件下的页岩气藏水平井和压裂水平井渗流模型,并求得了两种井型的无因次井底拟压力和无因次产量,绘制了压力和产量的典型曲线,进行了压力动态分析和产量递减分析。本文通过研究得到了以下成果： (1)通过对页岩气藏储层的地质特征、气体在页岩储层的赋存状态特征以及天然气在页岩基质和天然裂缝中的微观运移特征进行研究,研究结果表明页岩储层为特低渗、特低孔且极其致密的储层；吸附气的储集与储层岩石、气体性质和外部环境都存在关联,总的说来储层压力越高、温度越低、有机质成熟度越高、含水量越低,页岩储层中吸附气的储集条件就越好；生产中随着储层压力降低,吸附气从页岩基质表面解吸,并在基质中作对流和扩散综合作用下的扩散渗流,流向基质微孔隙或天然微裂缝。 (2)根据页岩气藏的储层特征、气体赋存状态特征以及储层中气体的微观运移特征,结合双重介质渗流机理,建立了双重介质页岩气藏非稳态渗流数学模型,并应用相应数学物理方法求得了连续点源解。在此基础之上建立了双重介质页岩气藏水平井渗流模型,并对其进行求解,绘制了无因次拟压力典型曲线和产量递减典型曲线,进行了压力动态和产量递减的敏感性分析。 (3)在结合双重介质页岩气藏非稳态渗流数学模型以及页岩气藏水平井渗流模型的基础上建立了适用于页岩气藏的压裂水平井渗流模型,并对其进行求解,绘制了双重介质页岩气藏压裂水平井的无因次拟压力典型曲线和产量递减典型曲线,进行了压力动态和产量递减的敏感性分析。 (4)通过对比页岩气藏水平井压裂前后的压力动态分布和产量递减趋势,结果表明压裂后拟压力典型曲线和产量递减典型曲线较压裂前总体趋势相同,但压裂后水平井的拟压力增长幅度变小、产量递减幅度变慢。
[Abstract]:Shale gas, as an unconventional energy source, has attracted worldwide attention due to its huge geological reserves, and has also made China pay more and more attention to the exploration and development of shale gas reservoirs. The characteristics of gas occurrence state and micro-migration of gas in reservoir make it very different from conventional gas reservoir, including shale reservoir is very low porosity, ultra-low permeability tight reservoir, Methane in shale gas reservoirs occurs in both adsorption and free states. The gas percolation modes in the reservoir include diffusion seepage and Darcy percolation. At present, the pressure dynamic analysis and production performance analysis of shale gas wells are mostly based on conventional dual media. The adsorption and diffusion term is usually neglected in gas reservoir percolation model. Based on the reservoir characteristics of shale gas reservoir, gas occurrence state and shale gas microscopic migration characteristics, a mathematical model of unsteady flow of shale gas reservoir with dual media is established in this paper. On the basis of Laplace transformation and point source function, the percolation models of horizontal well and fracturing horizontal well in shale gas reservoir under closed vertical roof and bottom and infinite horizontal direction are established respectively. The pseudo pressure and dimensionless production of two kinds of dimensionless wells are obtained, the typical curves of pressure and output are drawn, and the pressure dynamic analysis and production decline analysis are carried out. In this paper, the following results are obtained:. 1) by studying the geological characteristics of shale gas reservoir, the occurrence state of gas in shale reservoir and the microscopic migration characteristics of natural gas in shale matrix and natural fracture, the results show that the shale reservoir is extremely low permeability. The reservoir of adsorbed gas is related to reservoir rock, gas properties and external environment. Generally speaking, the higher the reservoir pressure, the lower the temperature, the higher the maturity of organic matter and the lower the water content. As the reservoir pressure decreases, the adsorbed gas desorbs from the shale matrix surface, and the diffusion and percolation of the gas in the shale matrix is carried out under the combined action of convection and diffusion. Flow to matrix micropores or natural microfractures. (2) according to the reservoir characteristics, gas occurrence state and gas microscopic migration characteristics of shale gas reservoir, combined with the mechanism of dual medium percolation, a mathematical model of unsteady percolation of shale gas reservoir with double medium is established. The continuous point source solution is obtained by using the corresponding mathematical and physical methods. On the basis of this, a horizontal well percolation model of dual medium shale gas reservoir is established and solved, and the dimensionless pseudo pressure typical curve and the production decline typical curve are drawn. Sensitivity analysis of pressure dynamics and production decline is carried out. Based on the mathematical model of unsteady percolation in shale gas reservoir with dual medium and horizontal well percolation model of shale gas reservoir, a fracturing horizontal well percolation model suitable for shale gas reservoir is established and solved. The dimensionless pseudo pressure typical curve and production decline typical curve of fractured horizontal well in dual medium shale gas reservoir are drawn, and the sensitivity analysis of pressure performance and production decline is carried out. 4) by comparing the pressure dynamic distribution and production decline trend before and after fracturing in shale gas reservoir horizontal wells, the results show that the typical pseudo pressure curve and the production decline typical curve after fracturing are the same as those before fracturing. But after fracturing, the pseudo-pressure increase range is smaller and the production decline range is slower.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE37

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