Parametric Investigation of the Gas-Assisted Gravity Drainage Technique

Abstract

Whereas the application of EOR methods is estimated to recover nearly 6 out of the 9 trillion barrels initially in-place globally, there is a high chance of failure of an EOR project due to lack of characterization, operational challenges, misplaced concept, etc. It is extremely challenging to reduce these uncertainties and hence the success of an EOR project is a big question, except for the case in which the method is relatively immune to such uncertainties. The gas-assisted gravity drainage (GAGD) technique is an excellent example of such a method where the recovery is enhanced by concepts of gravity and fluids' density differences and thus relatively safer from execution failures. It has been proposed as a viable alternative to, and improvement over, conventional gas injection techniques such as water-alternating-gas (WAG) and continuous gas injection (CGI), because of its higher chance of success. The success of GAGD hinges very strongly on the interplay between in-situ reservoir properties (rock and fluid parameters) and the range of operating parameters imposed. In the primary GAGD configuration, gas is injected in the crest, and oil is withdrawn (produced) via a horizontal well at the bottom of the structure. In this study, a simplified black-oil numerical simulation framework has been developed to assess the viability of the GAGD process in candidate reservoirs with focus around lower permeability reservoirs coupled with hydraulically fractured rocks. Incremental production over natural depletion and hydraulic fractured cases have been used as the assessment criterion.