Complete gas-brine imbibition relative permeability curves increase confidence in gas field performance

The standard methods used for measuring gas relative permeability during brine imbibition have been found to be inadequate as the resulting curves are incomplete and may include invalid points. CSIRO, together with an industry partner, developed new methods to improve on existing special core analysis, and generate substantially more complete gas relative permeability curves for samples from a NW Shelf gas field and also a Berea sandstone sample considered as a laboratory standard. The true relative permeability curve is typically 'S' shaped or has a rolling over, convex-up shape that is completely different from the concave-up shape of the Corey relperm curve usually fitted to SCAL test data and also assumed in reservoir simulations models as the default. Using the complete and more accurate relative permeability curves can give reservoir engineers more confidence in field development planning, and along the life of the field should result in better history matching. There may also be an economic upside if the reservoir produces gas at a high rate for longer than was originally predicted based on the old relperm curves.