基于返排数据计算页岩气井压裂有效体积的方法及应用

页岩气多段压裂水平井的缝网参数通常利用产气数据解释获得。虽然对产气数据进行解释能得到裂缝参数，但很难获得压裂有效体积。为快捷地获取页岩气井压裂有效体积，该研究建立了页岩气多段压裂水平井压裂液返排数学模型，并结合水相物质平衡方程和渗流方程，推导获得了页岩气井多段压裂水平井压裂有效体积表达式。通过分析模型解发现，在边界控制流阶段产量规整化压力与物质平衡时间双对数曲线为单位斜率直线，利用该阶段产量规整化压力及物质平衡时间数据，可以计算页岩气井压裂有效体积，从而形成了一套基于压裂液返排数据计算页岩气井压裂有效体积的方法。实例应用表明：(1)构建的页岩气多段压裂水平井压裂液返排模型能快速地计算页岩气井压裂有效体积，且计算结果可靠；(2)计算页岩气井压裂有效体积不能忽略试气期间的压裂液返排数据，否则计算结果偏小；(3)形成的页岩气井压裂有效体积计算方法还能识别邻井压裂干扰，并定量化表征邻井压裂干扰对页岩气井压裂有效体积的影响。该研究成果为油田现场估算页岩气井压裂有效体积提供了一种新的方法，同时也为油田现场识别邻井压裂干扰提供了新的思路和方法。

Method of estimating the effective fracture volume of shale gas wells using flowback data and its application

The fracture network parameters of multiple-fractured horizontal wells in shale gas reservoirs are usually obtained by interpretation of gas production data. However, it is difficult to obtain the effective fracture volume. In order to quickly obtain the effective fracture volume of shale gas wells, a fracturing fluid flowback model for multiple-fractured horizontal wells in shale gas reservoirs was established. Combining the water phase material balance equation and seepage equation, the expression for the effective fracture volume of multiple-fractured horizontal wells in shale gas reservoirs was derived. Analyzing the model solution, it was found that when water flowing enters the boundary dominated flow stage, the curve of the rate-normalized pressure and material balance time is a unit slope line in the double logarithmic coordinate. By using the rate-normalized pressure and material balance time data at this stage, the effective fracture volume of shale gas wells can be estimated. Based on this, a method for estimating the effective fracture volume of shale gas wells using fracturing fluid flowback data was proposed. The application examples showed that: (1) the fracturing fluid flowback model for multiple-fractured horizontal wells in shale gas reservoirs can quickly and reliably estimate the effective fracture volume of shale gas wells, and the results are credible; (2) the fracturing fluid flowback data during the gas testing period should be considered when estimating the effective fracture volume of shale gas wells, otherwise the results would be smaller than the actual results; (3) the proposed method can also be a means of recognizing and quantifying the fracturing interference effect of adjacent wells on the effective fracture volume of shale gas wells. The research results provide a new method for estimating the effective fracture volume of shale gas wells, and also provide a new idea and method for recognizing the fracturing interference of adjacent wells in oilfields.