Viscous pressure drop modulates the morphology of a network fractures activated by hydraulic stimulation
Abstract
Convective transport in low permeability rocks can be enhanced by injection of a fluid to activate pre-existing weak planes (fractures) above a critical fluid pressure given by Mohr's criterion. Using a discrete fracture network (DFN) simulation and complementary averaged equation solutions for a highly heterogeneous rock, we show that the morphology and average transport properties of a cluster of activated fractures depend on the ratio, FN, between the standard deviation of the critical pressures and the viscous pressure drop across a fracture. When FN << 1, the cluster is well connected, and a linear diffusion equation can be used to describe the cluster's growth. When FN>> R / l where R is the cluster radius and l is the fracture length, a fractal network is formed by an invasion percolation process. In the intermediate regime, 1 << FN << R/ l, percolation theory relates the porosity and permeability of the network to the local pressure and an averaged fluid transport equation with pressure-dependent properties describes the cluster growth on length scales much larger than lFN . The theory is also applicable to the displacement of a wetting fluid by a more viscous non-wetting fluid in a permeable rock with the capillary number replacing FN in the two-phase flow application.
Supported by NSF 1803156.- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- 2020
- Bibcode:
- 2020APS..DFDK14019K