Waterflood reservoir modelling for Chirag oilfield

Abstract

This article describes the studies carried out to determine the impact of all available laboratory measured oil-water relative permeability data upon the predicted waterflood performance of the Chirag field of the GCA megastructure. Sector and cross-section models were built of the A-6, A-11 and A-13 area using appraisal well GCA-1 core data. A-6 is the first well in Chirag field to have cut water and is the best candidate well for calibrating the laboratory relative permeability data. Simulations using various wateroil relative permeability curves predicted a wide range of water breakthrough times for A-6 and A-11. It was not possible to obtain a good history match of A-6 water production from core relative permeability curves. Grid size sensitivities were studied using a cross-section model. The results show that optimisation of grid size gives an improved match to the actual field history. Static reservoir parameters and aquifer size were also found to have a major impact on the waterflood performance and by adjusting certain key parameters a good history match to the historic A-6 performance could be achieved with the optimised grid. Keywords: Chirag; relative permeability; simulation sensitivity; cross-section model; reservoir description; grid-size; water breakthrough time; history matching.