The Propagation of Hydraulic Fractures in Fracture-Cavity Reservoir

Abstract:

In fracture-cavity reservoirs, natural cavities are main storage space for oil/gas. To enhance productions, it is necessary to generate connection between wellbores and natural cavities using hydraulic fracturing. In this work, the influences of natural cavities, natural fractures, geostress and injection pressure on hydraulic fracturing are investigated numerically by TOUGH-AiFrac simulator. This TOUGH-AiFrac links the TOUGH and FEMM. TOUGH2 is used to model the fluid flow in both fractures and porous rock, and AiFrac is used to simulate fracture propagation without remeshing. According to simulations, some useful conclusions can be drawn: (1) natural fractures have dominate influence on hydraulic fracturing(see Fig.1); (2) The nature caves with high pressure frequently forms tensile zone around itself, which attracts hydraulic fractures; (3) The hydraulic fractures frequently propagate and turn to the in the maximum geostress direction.

Key words: Fracture-cavity reservoir; TOUGH-AiFrac; natural cavities; natural fractures; hydraulic fracturing.