基于最小体积封闭椭球算法的多段水力压裂改造体积估算

Estimation of the Stimulated Reservoir Volume of Multi-stage Hydraulic Fracturing in Minimum Volume Enolosing Ellipsoid Algorithm

压裂改造体积(stimulated reservoir volume,SRV)是页岩油气开发的重要参数之一。为了解决在多段水力压裂作业过程中,不同压裂井段间压裂改造体积彼此重叠、单段压裂可能会形成复杂裂缝网络的问题。提出了基于最小体积封闭椭球算法(minimum volume enclosing ellipsoid,MVEE)的SRV估计算法。该算法首先使用DBSCAN(density based spatial clustering of applications with noise)算法消除微震事件的异常定位结果并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,结果表明:提出的方法对于多段压裂裂缝网络重叠和单段压裂可能形成复杂裂缝网络两类情况下的压裂改造体积的估算具有较好的效果。

Stimulated reservoir volume(SRV)is one of the important parameters in shale oil and gas industries.In practice,there are several problems in SRV estimation of multiple-stage hydraulic fracturing,such as hydraulic fracturing networks overlap among different stages,and complex hydraulic fracturing network in the single stage.To solve these problems,an SRV estimation was proposed based on minimum volume enclosing ellipsoid(MVEE)algorithm.First,density based spatial clustering of applications with noise(DBSCAN)was used to eliminate abnormal location results of microseismic events and convert complex distribution of microseismic events into multiple simple distribution groups.Then,MVEE was applied to calculate the SRV of each fracturing stage.Last,based on the parameters of each ellipsoid of every hydraulic stage,the overlap volumes of the SRVs could be calculated by using affine transformation among multiple fracturing stages or multiple groups of single fracturing stage.Two groups of field data were used to evaluate the validity of the proposed method.The processing results confirm the proposed method,indicating good performance of the proposed method.