Joint inversion of surface and borehole 4D gravity data for continuous characterization of fluid contact movement

In this paper, we demonstrate the feasibility of jointly inverting 4D gravity data collected on the surface and in a borehole setting to characterize fluid contact movement over time. As technology rapidly advances towards a practical borehole gravity meter capable of collecting data in horizontal monitoring wells, the foundations for properly inverting and interpreting these valuable data must simultaneously be developed. We demonstrate that 4D gravity method may contribute to improved production efficiency and reservoir management in-between the more traditional, and expensive, 4D seismic surveys. In our presentation, simulations are performed using a representation of the published Jotun Field in the Norwegian North Sea, a well-studied site demonstrating successful application of time-lapse (4D) seismic method after early rise in water cut, and therefore decline in production. Results demonstrate that 4D gravity monitoring in-between seismic surveys may have predicted this early water-cut at this site, thus providing additional valuable information to better optimize reservoir management.