Deep shale hydraulic fracture network volume model and its application

Due to the influence of burial depth, deep shale suffers high reservoir stress, large horizontal stress difference, difficult propagation of hydraulic fractures and limited stimulated reservoir volume. What’s more, the intra-fracture net pressure in the process of fracturing is low. As a result, the tension and shear fracture of natural fractures is more difficult and the complexity of fracture network is lower. The simplified 3D Wiremesh model was constructed to derive the distribution of fracture net fracture in different directions by considering the mechanical properties of orthogonal natural fractures and deep shale. Then, programming solution was carried out by means of Richtmyer linear method. Finally, the variation characteristics of fracture network volume at different parameters were figured out. It is indicated that with the increase of construction time, the fracture network volume increases approximately linearly and elliptic major/minor axis ratio increases continuously, but the propagation along the minor axis is limited in the late stage; with the increase of construction displacement, half fracture length and fracture network sweeping volume increase and the fracturing efficiency is improved significantly; the increase of fracturing fluid viscosity results in the increase of fracture width, the decrease of fracture length and the obvious reduction of fracture network volume; under the condition of uniform stress field, fractures propagate better in all directions, equivalent in major axis and minor axis, and the stimulated reservoir volume is smaller. The fracturing scheme optimized on the basis of the deep shale hydraulic fracture network volume model is applied on site in the deep wells of Jiangdong Block of Fuling Shale Gas Field 30 well times. The analysis on the postfrac G-function curve shows that the fracture complexity is high and testing pressure and testing production rate are higher, indicating satisfactory application effect. This study provides technical support for the stimulation of deep shale gas reservoirs.