A new numerical 3D-model for simulation of hydraulic fracturing in consideration of hydro-mechanical coupling effects

摘要

A new approach for simulating hydraulic fracture propagation, which treats fracture propagation in a 3D geometric model under 3D stress state with fully hydro-mechanical coupling, is introduced and integrated into the software FLAC3D. In the new modeling approach, the mechanical behavior of the rock formation is based on continuum mechanics. A modified tensile failure model has been used to describe fracture enlargement and closure. Meanwhile, a simplified fracture flow equation derived from the general Navier-Stokes equation and Darcy law, has been developed and used to describe fluid flow, both in the fracture and in the matrix. Fluid leakoff is no longer controlled by semi-analytical models, such as the Carter model, but resolved by means of numerical methods. In order to describe fracture propagation, the tensile failure criterion has been applied. To verify the new modeling approach, simulation of a laboratory test has been carried out. Numerical and measured results have been compared and found to be in agreement. After verification of the new modeling approach, a calculation, based on real data for a tight gas sandstone reservoir from the Northern German Basin, has been applied and graphically illustrated. Unlike conventional models, the new modeling approach not only considers the propagation of a single fracture, but also its influence on the adjacent rock formations and the neighboring fractures.