Abstract
History matching is challenging for low permeability gas reservoirs because of significant differences between the static properties in a geostatistical model and in-situ properties measured from well testing. The literature has documented that reduction of in-situ permeability due to overburden pressure can be in two orders of magnitude. Numerical well testing provides a way of tuning a static model with dynamic well testing information. However, a traditional single well testing model using Cartesian LGR (local grid refinement) is not ideal for predicting the pressure transient behavior. Furthermore, a stand-along well testing conditioned model cannot be fully coupled into a full-field model to honor the flow regime.
This paper presents a methodology of using a PEBI (perpendicular bisector) grid in a simulation model to match well test data for a low permeability gas reservoir in Canadian Foothills. A PEBI-LGR grid is created around the well and a vertical hydraulic fracture is implemented to match the post fracture pressure build up. History matched parameters include static properties and hydraulic fracture properties such as fracture half length and fracture permeability. Finally, well testing conditioned effective properties will be stochastically populated into the simulation model for the full field history matching. In conclusion, the PEBI gridding technique links well testing with reservoir simulation and provides the most efficient workflow in modeling unconventional gas reservoirs with multi-stage hydraulic fractures.
