页岩气井返排早期气水两相流数学模型研究

发布时间：2018-10-12 11:22

【摘要】：目前存在的早期单相流返排的数学模型适用于致密油气储层,不适用于页岩气储层,这是因为页岩气井早期返排阶段不存在单相流,而是气水两相流。利用北美某页岩气储层压裂水平井的返排数据分别绘制气水产量随时间的变化曲线和气水比随累积产气量的变化曲线,气水产量曲线在早期返排阶段气水同产,表明裂缝中存在自由气的消耗;而气水比曲线根据斜率的正负将返排分为两个阶段,并针对曲线的"V型"进行原因分析。针对气体早期返排阶段,建立裂缝系统物理模型,运用物质平衡方程和扩散方程,推导得到页岩气井早期两相流返排数学模型,数学方程表明:等效压力与拟时间呈线性关系。应用现场实例对数学模型进行分析,结果表明,该模型能够较好地拟合现场数据,拟合得到的直线斜率可用于估算原始裂缝体积,截距可以给出裂缝半长和裂缝渗透率之间的关系。本文创新性地对返排数据进行调研分析,在此基础上得出适用于现场估算裂缝参数的返排数学方程,从而为认识裂缝特征提供了新的方法。
[Abstract]:The present mathematical model of early single-phase flow backflow is suitable for tight oil and gas reservoirs, but not for shale gas reservoirs. This is because there is no single phase flow in the early stage of shale gas well reflux, but gas-water two-phase flow. Based on the back discharge data of fracturing horizontal wells in a shale gas reservoir in North America, the variation curves of gas and water production with time and the ratio of gas to water with cumulative gas production are plotted respectively. It shows that there is free gas consumption in the fracture, and the gas-water ratio curve is divided into two stages according to the positive and negative slope, and the reasons for the V-shape of the curve are analyzed. The physical model of fracture system is established for the early stage of gas reflux, and the mathematical model of two-phase flow backflow in the early stage of shale gas well is derived by using the material balance equation and diffusion equation. The mathematical equation shows that the equivalent pressure is linearly related to the pseudo-time. The results show that the model can fit the field data well, and the straight line slope can be used to estimate the original crack volume. Intercept can give the relationship between fracture half length and fracture permeability. Based on the investigation and analysis of the backflow data, a mathematical equation of backflow is obtained, which is suitable for the field estimation of fracture parameters, thus providing a new method for understanding the fracture characteristics.
【作者单位】：中国石油大学(北京)石油工程学院;
【基金】：国家自然科学基金(41672132)资助
【分类号】：TE312

【相似文献】