Modeling the Feasibility of Gas-Water or Gas-Oil Contact Control by Microgravity Monitoring during Enhanced Oil Recovery

Monitoring of fluids in reservoirs has become an essential tool for the control of active hydrocarbon fields, including EOR process. Repeated microgravity (time-lapse gravity, 4D gravity) can determine especially gas-water or gas-oil contact displacement in time. The technique can also be used in industrial and construction areas, contrary to 4D seismic and electromagnetics. The efficiency of the technique has been already proven by successful time-lapse gravity surveys, e.g. in Alaska, France, Italy, Oman and Qatar. Based on experience from water penetration to a sandstone formation in Egypt, gravity modelling was performed to simulate gas - water/oil contact movement in reservoirs related to pumping, water-flooding, etc. Various reservoir parameters were changed - depth, thickness, geometry, porosity and density. Gas or steam injecting/pumping was investigated, too. It was found that such processes can be observed by time-lapse microgravity, but the success depends on local geological conditions and reservoir parameters. New complex feasibility parameter cF was developed and established in graphic and tabular forms based on the time- and space-domain 3D and 4D gravity modelling. This parameter should provide fast pre-survey estimation of the effectiveness of microgravity monitoring. This procedure has not been developed before.