基于压裂液返排动态数据的页岩气井气–水相渗规律反演

Inversion of Gas-Water Phase Seepage Law of Shale Gas Wells Based on Dynamic Data of Fracturing Fluid Flowback

摘要: 相对渗透率曲线是研究气–水两相渗流规律的基础，在气田动态分析、气藏数值模拟和预测未来产水产气趋势有重要作用，应用范围广；为了页岩气的高效开采，必须对储层进行压裂改造、形成复杂裂缝网络，提高近井地带储层渗透率。由于当前室内模拟实验中，无法准确模拟压裂对储层的影响，导致对压裂液返排过程中气–水相渗规律研究准确度不足。本文通过理论公式，推导了新的含水饱和度计算方法，进而根据分形模型，改进了平均含水饱和度的获取方式，从而建立了页岩气井压后气–水相渗模型。根据最小二乘法，反演了四川盆地某区块W1井的相渗曲线。研究表明，基于动态数据反演的相渗曲线R² = 0.9785，RMSE = 0.1239。拟合效果好，准确率高。可以较好应用于气藏数值模拟中。

Abstract: The relative permeability curve is the basis for studying the laws of gas water two-phase flow, and plays an important role in dynamic analysis of gas fields, numerical simulation of gas reservoirs, and prediction of future water and gas production trends. It has a wide range of applications; in order to efficiently extract shale gas, it is necessary to carry out fracturing transformation on the reservoir, form a complex fracture network, and improve the permeability of the reservoir near the wellbore. Due to the inability to accurately simulate the impact of fracturing on reservoirs in current indoor simulation experiments, the accuracy of studying the gas water phase permeability law during the fracturing fluid backflow process is insufficient. This article derives a new method for calculating water saturation through theoretical formulas, and improves the method of obtaining average water saturation based on fractal models, thus establishing a gas water permeability model for shale gas wells after pressure. According to the least squares method, the relative permeability curve of well W1 in a certain block of the Sichuan Basin was inverted. Research has shown that the permeability curve based on dynamic data inversion has R² = 0.9785 and RMSE = 0.1239. Good fitting effect and high accuracy. It can be well applied in numerical simulation of gas reservoirs.