Numerical Simulation of Hydraulic Fracturing in Tight Gas Shale Reservoirs

Hydraulic fracturing of tight gas shales is a relatively new method of producing economically
from extremely low permeability reservoirs. Due to the low permeability, it is crucial
that fracturing treatments are able to efficiently create regions of enhanced permeability
in the reservoir. The mechanical properties of prospective shale mean that stress interactions
between adjacent fractures can be of real consequence to the efficiency of the
treatment, and alternative treatments to mitigate these effects have been designed.
The aim of this research is to conduct numerical simulation of alternative treatment designs,
and objectively evaluate critical parameters. In particular, key aspects of the socalled
Texas Two Step method are simulated. This treatment aims to create zones of
altered stress anisotropy between pressurised fractures. This study examines the behaviour
of said zones as the distance between the fractures is altered, in parallel with
literature describing the method. Explanations for unusual fracture curvature behaviour
are provided.
Further studies examine fracture reorientation within a modified stress field such as that
created by the treatment. Rates of reorientation are measured under varying levels of
stress anisotropy, initial fracture length and orientation to the stress field.
The influence of pre existing natural fractures on the path of a hydraulic fracture is investigated
through further simulations. The effects of natural fracture permeability and
interface properties are studied. The impact of shear stress caused by a propagating
fracture is also examined, and the possible implications for interpretation of microseismic
data discussed.
Finally, a new treatment for simultaneous fracturing with reduced stress shadowing is
proposed and simulated.