基于最小体积封闭椭球算法的多段水力压裂压裂改造体积估算

压裂改造体积(Stimulated Reservoir Volume, SRV)是页岩油气开发的重要参数之一。在多段水力压裂作业过程中，会存在不同压裂井段间压裂改造体积彼此重叠和单段压裂可能会形成复杂裂缝网络的问题。针对这两种情况，本文以微震事件的展布特征为基础，首先使用DBSCAN(Density Based Spatial Clustering of Applications with Noise)算法消除微震事件的异常定位结果和将复杂微震事件展布进行分组处理，转化为多组分布特征相对简单的微震事件，然后使用最小体积封闭椭球算法(Minimum volume enclosing ellipsoid, MVEE)估算单段压裂改造体积，最后基于椭球体参数，利用仿射变换消除多段压裂改造体积的重叠区域和单段压裂的不同分组间的重叠区域，并最终估算出整体压裂改造体积。使用两组实测水力压裂微震监测数据对本文方法进行了验证，并证明了该方法的有效性。

Estimation of the Stimulated Reservoir Volume of Multi-stage Hydraulic Fracturing Based on MVEE

Stimulated reservoir volume is an important parameter of the development for shale gas and oil reservoirs. During the production of multi-stage hydraulic fracturing, kinds of problems may be countered. For example, there are many overlap fracturing zones among stages, and complex fracture networks may be created. The processing flow is proposed to estimate the stimulated reservoir volume of multi-stage fracturing. At first, DBSCAN algorithm is used to eliminate the outliers and divide the complex distribution into several sub-distributions for calculating the SRV of the complex distribution. Then, MVEE algorithm is used to calculate SRV based on microseismic event distributions. At last, the volume of overlap zone is calculated by using affine transformation with the parameters of ellipsoid. So, the overall stimulated reservoir volume can be obtained. Two groups of field data are used to evaluate the proposed method. The processing results confirm the validity of the proposed method.