The Effects of Geomechanics on the WAG Injection Model

Abstract

Geomechanics is the study of the rock elastic or plastic behavior and has direct impact on well integrity. Wellbore instability is a serious drilling problem that costs the oil industry over US$500–1000 million each year. Over the past two decades the geo-mechanical analysis has made major changes in the petroleum industry by maximizing production and increasing the life of the well. Water alternating gas (WAG) injection has been a popular method for commercial gas injection projects worldwide. The main objective of this paper is to determine the effects of geomechanics on reservoir flow for the water alternating gas (WAG) process. The WAG injection pressure, temperature and the initial in-situ stress is important to determine the stress after the injection. The change in stress changes the porosity, permeability and subsequently the flow pattern changes. There are some methods to investigate the effects of geomechanics on reservoir simulation, as implicit, explicit, iterative and psudo-coupling method. In this study we use the iterative coupling method. In this type of coupling, reservoir flow variables and geomechanics variables are solved by a reservoir simulator and a geomechanics module, and the coupling terms are iterated on at each time step. The results show the difference in the flow patterns, porosity and permeability with and without considering the geomechanics.