Feasibility of time-lapse gravity gradiometry for reservoir monitoring.

摘要

Monitoring fluid movement within a reservoir is essential to ensuring efficient reservoir development. To date, time-lapse monitoring has been dominated by seismic technology, but there is a desire to find additional technologies that can supplement seismic data and potentially lower the overall monitoring cost. Potential field methods, such as gravity and gravity gradiometry, may be suitable for time-lapse monitoring due to their ability to track fluid through density changes within the reservoir. While gravity has been previously studied, there has been very little work done in the field of time-lapse gravity gradiometry. In this thesis, I present a series of feasibility studies designed to determine whether or not gravity gradiometry is capable of detecting the small density contrasts associated with various reservoir monitoring problems. Here, considering both the current and predicted next generation of gravity gradiometry technology, I evaluate the signals from a variety of conventional and unconventional reservoirs to understand the potential value at these different sites. I likewise analyze the ability of gravity gradiometry to recover fluid movement by inversion for a set of specific reservoir sites that contain detailed site geometries developed from seismic data and prior site studies. The results of this work indicate that gravity gradiometry may provide a powerful tool for reservoir monitoring in the near future. However, as with all geophysical methods, the true application is site dependent as the final signal will vary based on the reservoir's fluid densities, saturations, depths, thicknesses and other parameters.