基于超临界吸附模型的页岩气藏压裂水平井开采动态研究

发布时间：2018-01-03 04:13

本文关键词：基于超临界吸附模型的页岩气藏压裂水平井开采动态研究　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：我国页岩气可采资源量丰富,位居世界前列,经济价值巨大。页岩气藏不同于常规气藏,其赋存形式与渗流机理复杂,主要以游离态和吸附态存在于多孔孔介质中,包含吸附气解吸特征和达西、滑脱和扩散等渗流特征。页岩气吸附解吸现象对页岩气藏的开发开采有着重要的影响。因此,深入研究页岩气在地层条件下的超临界吸附解吸现象以及页岩气藏压裂水平井开采动态,对于经济高效地开发页岩气资源具有重大的理论价值和现实意义。本文采用实验与理论相结合的方法开展研究。首先,开展了页岩气等温吸附实验,并推导出高温高压条件时页岩气处于超临界状态下的等温吸附模型,并进行验证。同时,建立了适用于页岩气藏的多尺度综合渗流方程,在考虑气体解吸、多重流动机制以及压裂水平井生产的基础上,建立了页岩气藏气-水两相三维计算机模型,并进一步探讨了Knudsen扩散和滑脱效应、等温吸附参数、超临界等温吸附模型、气-水两相流动以及压裂增产措施对压裂水平井产量的影响。本文主要的工作与结论如下:(1)对页岩气储层微观孔隙结构、气体储集方式以及运移机理进行了理论研究,分别从不同尺度对页岩气的运移及产出机理进行了物理描述及数学表征。(2)开展了页岩气等温吸附实验。测试不同的页岩岩样在不同温度下的等温吸附曲线。页岩气等温吸附曲线表明,当实验压力由OMPa升高到3MPa时,页岩气的吸附量成指数式上升;随着压力的继续增大,页岩气吸附量的增长速度逐渐变缓。页岩气吸附量随着温度的增加而降低。当温度从25℃升高到40℃时,四块页岩岩样吸附气量平均减少了 12.23%;当温度从40℃升高到60℃时,页岩气吸附量平均减少了 38.86%。(3)在超临界状态下测定的页岩气的吸附量为过剩吸附量,结合Gibbs吸附与Langmuir吸附模型,得到修正的Langmuir模型。考虑到页岩气在有机质内部的吸附量,提出了 L-K吸附模型。对各种等温吸附模型进行了拟合及对比研究,表明L-K模型对页岩等温吸附曲线的拟合程度比其他模型的拟合程度都高;在高温高压条件下,L-K模型的拟合精度比Langmuir模型拟合精度平均高出11.21%。(4)建立了适用于页岩中不同流态的多尺度综合渗流方程,在考虑纳米孔隙中的Knudsen扩散和滑脱效应、超临界吸附解吸以及气-水两相流动的基础上,通过有限差分方法及计算机程序编制得到页岩气藏的三维计算机模型,并通过网格加密以及采用等效导流能力方法来模拟人工压裂裂缝对气体流动的影响。(5)利用Eclipse软件和现场数据验证了本文理论模型的可靠性和适用性,分析了压裂水平井的生产动态,并研究了 Knudsen扩散和滑脱效应、气体的解吸作用、气-水两相流动、超临界等温吸附模型、多级压裂水平井的相关参数对产量的影响。本文的研究成果可为页岩气井的生产动态分析及产能预测提供理论基础、为指导页岩气藏高效开发提供理论依据。
[Abstract]:China's shale gas recoverable resources are abundant, the highest in the world, a huge economic value. Shale gas reservoir is different from conventional gas reservoirs, its occurrence and seepage mechanism is complex, mainly in the free state and the adsorption state exists in porous medium, including adsorption desorption characteristics of gas diffusion and Darcy, slip and seepage characteristics. Has an important effect on adsorption and desorption of shale gas exploitation phenomenon of shale gas reservoirs. Therefore, supercritical adsorption desorption phenomenon in-depth study of shale gas in the formation conditions of shale gas fracturing horizontal well production dynamic, for economic and efficient development of shale gas resources has great theoretical value and practical significance. This paper uses the method of combining experiment with theoretical research. First of all, the development of shale gas isothermal adsorption experiment, adsorption isotherm model under supercritical condition of shale gas in high temperature and high pressure conditions are derived, And verified. At the same time, the multi-scale comprehensive seepage equation was established for shale gas reservoirs, considering gas desorption, multiple flow mechanism and production of fractured horizontal well, established shale gas water two phase 3D computer model, and further discusses the Knudsen diffusion and slippage effect, adsorption isotherm parameters. Supercritical adsorption isotherm model, effect of gas water two-phase flow and fracturing of fractured horizontal well production. In this paper, the main work and conclusion are as follows: (1) for shale gas reservoir microscopic pore structure, reservoir and gas migration mechanism were studied, respectively from the migration and production mechanism of different scales shale gas is presented and mathematical representation. (2) the shale gas adsorption isotherm experiments. The isothermal adsorption curves of shale samples tested at different temperatures. The shale gas adsorption A curve shows that when the pressure increased from OMPa to 3MPa, the adsorption capacity of shale gas into exponential rise; as the pressure increases, the adsorption of shale gas volume growth rate gradually slowed. Shale gas adsorption amount decreases with increasing temperature. When the temperature rises from 25 C to 40 C, four the shale rock adsorption volume was reduced by 12.23% on average; when the temperature rises from 40 degrees to 60 degrees, the average amount of shale gas adsorption decreased by 38.86%. (3) adsorption measurement in supercritical condition of shale gas for excess adsorption, with Gibbs adsorption and Langmuir adsorption model, obtained the modified Langmuir model is considered. The adsorption capacity of shale gas in the organic matter within the proposed L-K adsorption model. The adsorption isotherm model of fitting and comparison, shows that the L-K model of shale isothermal adsorption curve fitting degree than the other model fitting degree High; under high temperature, the fitting precision of L-K model than the Langmuir model fitting precision is higher than the average 11.21%. (4) multi-scalesynthetical seepage equation was established for different flow patterns in shale, considering the Knudsen diffusion and slippage effect nano pores, adsorption and desorption of supercritical gas water two-phase flow on the three-dimensional computer model of shale gas reservoir by finite difference method and the computer program, and through the grid encryption and the equivalent conductivity method to simulate the influence of artificial fracture on gas flow. (5) to verify the reliability of the theoretical model and the applicability of using Eclipse software and field data analysis the production performance of fractured horizontal well, and the Knudsen diffusion and slippage effect, gas desorption, gas water two-phase flow, supercritical adsorption isotherm model, multi stage fracturing level The influence of relevant parameters of well on output is discussed. The research results in this paper can provide theoretical basis for production dynamic analysis and productivity prediction of shale gas well, and provide theoretical basis for effective 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】：TE377

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