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. Keywords:Hydraulic fracture complexity; tilt magnitude; ratio of fluid volume to fracture volume; fracture complexity index; unconventional reservoir Background As shale gas and shale oil are developed successfully, unconventional oil and gas resources have attracted more attention. Currently, the unconventional oil and gas production worldwide is mainly from the coalbed methane, shale gas, shale oil. All these resources must be stimulated by hydraulic fracturing in order to achieve economic production rates. However the hydraulic fractures in these reservoirs become very complicated due to the unconventional reservoir lithology and mechanical properties (1) , and the TX 75083-3836, U.S.A., fax +1-972-952-9435

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