基于非线性介质耦合的多级压裂水平气井产能研究

发布时间：2018-04-30 13:06

本文选题：致密气藏 + 多级压裂　；参考：《西南石油大学》2017年硕士论文

【摘要】：致密气藏通常采用多级压裂水平井技术进行开采,准确评价多级压裂水平井产能对于致密气藏开采具有重要意义。许多学者在开展多级压裂水平井产能评价过程中借助线性介质耦合机制考虑渗透率应力敏感性的影响,然而,部分学者研究证实致密砂岩储层的有效应力表现为非线性,用线性介质耦合代替非线性介质耦合描述致密气藏砂岩特征必然会产生严重错误,因此,有必要基于非线性介质耦合开展多级压裂水平井产能评价工作。本文针对含微裂缝和人造裂缝的致密砂岩开展了特殊应力敏感实验以及变围压实验,根据变围压实验结果确定渗透率与有效应力相关关系,同时根据特殊应力敏感实验结果结合响应面法认清非线性介质耦合机制,进而结合非线性有效应力方程将变围压实验结果转换为渗透率与内压关系,并将其与变内压实验结果进行了对比。此外,考虑非线性介质耦合的产能模型中渗流偏微分方程是高度非线性的,运用解析法对其进行求解存在一定难度,此时需要适用性更强的半解析方法。本文基于不同介质耦合形式建立了箱型气藏中一口多级压裂水平井的数学模型,并通过离散网格的方式将非线性项平均到各网格,进而通过Laplace变换及Newman乘积等方法对单个网格数学模型进行解析求解,最后结合网格间连续性条件耦合求解了产量分布,进一步结合实例数据评价了裂缝参数的影响。通过研究,形成了一套基于非线性介质耦合来考虑渗透率应力敏感性的方法,并基于该方法形成了多级压裂水平井不稳定产能预测及分析方法,进一步深化了致密气藏中渗流机理及不稳定状态下生产动态特征的认识,为正确使用有效应力、致密气藏工作制度确定以及多级压裂裂缝参数优选提供了依据。
[Abstract]:The multistage fracturing horizontal well technology is usually used to produce the tight gas reservoir. It is very important to evaluate the productivity of the multistage fracturing horizontal well accurately for the tight gas reservoir production. Many scholars consider the influence of permeability stress sensitivity by means of linear medium coupling mechanism in the process of productivity evaluation of multistage fracturing horizontal wells. However, some scholars have confirmed that the effective stress of tight sandstone reservoir is nonlinear. It is necessary to use linear medium coupling instead of nonlinear medium coupling to describe sandstone characteristics of tight gas reservoirs, so it is necessary to carry out productivity evaluation of multistage fracturing horizontal wells based on nonlinear medium coupling. In this paper, special stress sensitive experiments and variable confining pressure experiments have been carried out for compact sandstone with microfractures and artificial fractures. The relationship between permeability and effective stress is determined according to the experimental results of variable confining pressure. At the same time, according to the results of special stress sensitivity experiment and response surface method, the coupling mechanism of nonlinear medium is recognized, and then the experimental results of variable confining pressure are converted into the relationship between permeability and internal pressure by combining with nonlinear effective stress equation. It is compared with the experimental results of variable internal pressure. In addition, the partial differential equation of percolation is highly nonlinear in the productivity model considering the coupling of nonlinear medium. It is difficult to solve it by using analytical method, and a more applicable semi-analytical method is needed. In this paper, a mathematical model of a multistage fracturing horizontal well in a box gas reservoir is established based on different medium coupling forms, and the nonlinear term is averaged to each grid by means of discrete grid. Then the mathematical model of a single grid is analytically solved by means of Laplace transformation and Newman product. Finally, the output distribution is solved by coupling the continuity conditions between grids, and the influence of crack parameters is evaluated by the example data. Through the research, a set of methods based on nonlinear medium coupling to consider permeability stress sensitivity are developed. Based on this method, a method for predicting and analyzing unstable productivity of multistage fracturing horizontal wells is developed. It further deepens the understanding of percolation mechanism and production characteristics under unstable state in tight gas reservoirs, which provides a basis for the correct use of effective stress, the determination of working rules for tight gas reservoirs and the optimal selection of fracture parameters for multistage fracturing.
【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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