ABSTRACT:

During the process of fracturing the layered tight gas reservoirs with shale barriers, the propagation of hydraulic fractures can be significantly affected by the geological factors and operation parameters. In this paper, a three-dimensional fracture height model of layered tight gas reservoirs is presented to investigate how these factors influence the geometries of hydraulic fractures. A typical hydraulic fracturing process of a vertical well in Ordos basin, China is simulated with this model. The result shows that vertical fractures are mainly formed during the treatment, and the fracture height is dominated by in-situ stress. Stress difference higher than 4MPa shows great effectiveness in fracture height containment. In addition, the result indicates that lower elastic modulus is favorable for fracture height containment while Possion’s ratio has almost no effect. Fracture propagation is strongly inhibited with injection rates lower than 6m3/min under stress difference higher than 4MPa. When stress difference is no more than 2MPa, the fracture height grows well with increasing injection rates. Fluid viscosity lower than 10mPa•s has negligible impact. Perforation location plays an important role in the fracture initiation stage. Fracture geometries differ distinctly with varied perforation locations.

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