A 3D numerical model for investigation of hydraulic fracture configuration in multilayered tight sandstone gas reservoirs

Multilayered tight sandstone gas reservoirs with low porosity and low permeability are usually developed by two kinds of hydraulic fracturing techniques, including general fracturing (simultaneously fracturing multiple target zones) and separate layer fracturing (sequentially fracturing the target zones from the bottom-up). However, fractures from different target zones are likely to communicate in the fracturing process which detrimentally causes the waste of fracturing fluid and proppants and finally affects the efficiency of fracturing treatment. Therefore, investigation related to hydraulic fracture configurations under different fracturing stimulation treatments is necessary with the objective of optimizing the fracturing design and predicting the production rate. In this paper, a 3D finite element model is established to simulate the propagation of multiple hydraulic fractures in the vertical well, and fracture configurations under different fracturing techniques and formation properties are analyzed and compared. The results indicate that, in vertical wells, stress interference between the fracture tips will accelerate the communication of adjacent vertical fractures along the height direction. And separate layer fracturing is preferable for stimulating multilayered tight sandstone gas reservoirs. Also, adjacent pay zones and barriers with high in situ stress contrast, high tensile strength contrast and low elastic modulus contrast are able to effectively prevent the communication of fractures along the height direction and lead to the increase of fracture length and width, and so does the barriers with large thickness.