页岩气藏产量递减分析及预测方法研究

发布时间：2018-02-20 04:01

  本文关键词： 页岩气藏 压裂水平井 非稳态渗流 递减分析 产量预测　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：在当前国际能源供需矛盾日渐突出的情势下,新能源的有效开采对国家战略部署具有重要的意义,而页岩气作为一种新非常规能源,尤其是北美国家成功开发之后,备受世界各国的关注。论文以页岩气藏储层特征及渗流规律为基础,分析了页岩基质表观渗透率和裂缝渗透率的变化特征,建立了考虑页岩基质中气体多尺度渗流及裂缝应力敏感效应的非稳态渗流方程,进一步推导出无限大页岩气藏非垂直压裂水平产量递减模型,并通过Stehfest数值反演及Visual Studio 2012软件编程对产量递减规律进行敏感性分析。同时也对页岩气藏产量预测方法进行了相关研究,深入分析各预测模型建立的理论基础,参数取值范围和递减率变化规律,通过实例计算分析了拟合时长对预测结果的影响,并基于实际应用过程中发现的问题给出了相应的修正及优化方法。通过对上述内容研究之后,得到以下认识及结论:(1)页岩中矿物含量的相对大小,会直接影响页岩气的储集和储层缝隙的发育情况,黏土矿物含量越多,提供的吸附表面积就越多,有利于页岩气储集,而脆性矿物含量越多,越有利于储层微裂缝的发育,对气体渗流有着重要的意义。(2)页岩基质孔径大小多处于微米级和纳米级,使气体渗流呈现微尺度效应,滑脱效应和扩散作用对渗流的影响不可忽略,以气体分子与孔隙壁面碰撞为系数,得到页岩基质气体渗流的表观渗透率数学关系式,同时以平板缝模型建立了裂缝渗透率变化关系式。(3)综合考虑页岩基质多尺度渗流、解吸作用及裂缝应力敏感效应,建立了页岩气藏双重介质非稳态渗流方程,通过数学变换得到无限大非垂直压裂水平井产量递减模型,应用Visual Studio 2012编程计算,分析各因素对产量递减规律的影响,结果表明:储容比越大,初期产量就越高,产量递减越慢;不考虑吸附作用和考虑吸附作用主要会影响窜流阶段之后的渗流阶段,且吸附作用越强,产量越大,递减越慢;裂缝数量会影响整个渗流阶段,且裂缝条数越多,产量就越大;裂缝半长越大,初期产量越高;基质渗透率修正系数越大,产量越大,递减越慢;而裂缝应力敏感效应主要影响生产后期,渗透率模型越大,产量递减越快。(4)拟合时间越长,模型预测结果越准确,拟合时长较短时,Duong模型预测结果相对较为准确,PLE模型次之,SEPD模型较差;随着拟合时长增加,PLE模型预测误差迅速减小。PLE模型在拟合求解参数时,若不定义参数的取值范围,有可能会导致计算出的参数值出现错误;Duong模型累计产量关系式中,参数q∞并不是定值而是随时间变化的变量。为减少预测结果的风险,基于组合理论提出页岩气藏最优组合产量预测方法,并通过实例计算验证了该方法的可行性。
[Abstract]:In the current international energy supply and demand situation, the effective exploitation of new energy is of great significance to the national strategic deployment, and shale gas as a new unconventional energy, especially after the successful development of North American countries, Based on the reservoir characteristics and percolation law of shale gas reservoir, the change characteristics of apparent permeability and fracture permeability of shale matrix are analyzed. The unsteady seepage equation considering gas multi-scale seepage and fracture stress sensitivity in shale matrix is established, and the non-vertical fracturing horizontal production decline model of infinite shale gas reservoir is further deduced. Through Stehfest numerical inversion and Visual Studio 2012 software programming, sensitivity analysis of production decline law is carried out. At the same time, the production prediction method of shale gas reservoir is studied, and the theoretical foundation of each prediction model is deeply analyzed. The variation law of parameter range and decline rate is analyzed. The effect of fitting time on the prediction results is analyzed by an example. The corresponding correction and optimization methods are given based on the problems found in the practical application. After studying the above contents, the following conclusions are obtained: the relative size of mineral content in shale. It will directly affect the reservoir of shale gas and the development of reservoir crevice. The more clay mineral content, the more adsorption surface area will be provided, which is beneficial to shale gas reservoir, and the more brittle mineral content, the more favorable to the development of reservoir microfractures. The pore size of shale matrix is mostly in the micrometer and nanometer order, which makes the gas percolation appear microscale effect, and the influence of slippage effect and diffusion action on the percolation can not be ignored. Taking the collision of gas molecules with pore wall as the coefficient, the mathematical expression of apparent permeability of shale matrix gas seepage is obtained. At the same time, based on the flat fracture model, the relationship between fracture permeability and fracture permeability is established, and the multiscale seepage of shale matrix is considered synthetically. The unsteady seepage equation of shale gas reservoir with dual medium is established by desorption and fracture stress sensitive effect. The production decline model of infinite non-vertical fracturing horizontal well is obtained by mathematical transformation. The calculation is programmed by Visual Studio 2012. By analyzing the influence of various factors on the law of production decline, the results show that the higher the ratio of storage to capacity, the higher the initial production and the slower the decline of production, and the failure to consider adsorption and adsorption will mainly affect the percolation stage after the channeling stage. And the stronger the adsorption action, the larger the yield, the slower the decline, the more the number of fractures will affect the whole seepage stage, and the more the number of fractures, the larger the yield, the larger the fracture half length, the higher the initial production, the greater the matrix permeability correction coefficient, the greater the yield. The effect of fracture stress sensitivity mainly affects the later stage of production, the larger the permeability model is, the faster the production decline is, the longer the fitting time is, the more accurate the prediction results are. With the increase of fitting time, the prediction error of PLE model decreases rapidly. When fitting and solving parameters, if the range of parameters is not defined, the prediction results of Duong model with shorter fitting time are less accurate than that of SEPD model. In the cumulative output relation of Duong model, the parameter Q 鈭，

本文编号：1518715