A New Method to Interpret Hydraulic Fracture Complexity in Unconventional Reservoir by Tilt Magnitude

Hydraulic fractures in unconventional reservoir are complex. Surface tilemeter fracture mapping method is used to obtain ground deformation field caused by hydraulic fracture. The observed and theoretical fracture-induced tilt vectors from a best-fit fracture solution are compared and obtain hydraulic fracture orientation and shape. Through analysis of the vertical and horizontal component volume, three new parameters are given to characterize the fracture complexity, i.e. ratio of fluid volume to fracture volume R; volume weight difference rate D and fracture complexity index β. These new parameters are used to explain the mapping result of shale and coal seam reservoir. The results show that R of coal bed and shale is 2.2 and 2.9 while sandstone is only 1.4. β of shale, coal bed and sandstone are 0.7,0.4 and 0.3 respectively, the two new parameters show hydraulic fractures in unconventional reservoir are very complex. The new parameters can describe fracture complexity very well, and results are correlated well with the results of fracturing pressure analysis and other methods of monitoring. This method provides valuable information for optimizing fracturing treatment design and postfrac evaluation in unconventional reservoir.