Reservoir Compaction and Fluid Leakoff During Fluid Injection Operations

Fluid loss into reservoir rocks during hydraulic fracturing is modeled via a poro-elastoplastic pressure diffusion equation in which the total compressibility is a sum of fluid, rock and pore space compressibilities. Inclusion of pore compressibility and porosity-dependent permeability in the model leads to a strong pressure dependence of leakoff. Dilation of the matrix due to fluid invasion causes higher rates of fluid leakoff. We suggest that certain features of leakoff behavior might give an indication of the significance of the reservoir compaction/decompaction during fluid injection operations and distinguish different types of rock deformation (linear poroelastic, nonlinear poroelastic, poroelastoplastic).