Understanding the applications and limitations of time-lapse gravity for reservoir monitoring

Abstract

There is a strong need in our industry for advancing the understanding and applications of multiple geophysical techniques for time-lapse problems, such as for [Formula: see text]S sequestration and enhanced oil recovery (EOR) projects. Currently, monitoring efforts for such activities are dominated largely by 4D seismic, and there are numerous developments and successful applications throughout the geophysical literature to justify this state of affair (e.g., Lumley, 2010). The primary advantage of 4D seismic for these endeavors is that it can provide a high-resolution imaging tool that allows better reservoir management decisions and improved production efficiency.

Higher Resolution Subsurface Imaging

“…This technique was meticulously applied over Prudhoe Bay, Alaska, for a period from 2003 to 2007 to confirm a microgravity signal to enable water flood sur-veillance in the giant field (Ferguson et al, 2008). Modeling work to track CO 2 injection for sequestration and enhanced oil recovery shows a time-lapse microgravity signal when oil and water are displaced, consistent with an independent analysis with seismic data (Krahenbuhl et al, 2011). Modeling work to track CO 2 injection for sequestration and enhanced oil recovery shows a time-lapse microgravity signal when oil and water are displaced, consistent with an independent analysis with seismic data (Krahenbuhl et al, 2011).…”

“…Time-lapse microgravity technology shows promise as a low-cost alternative to 4D seismic for shallow reservoirs as instrumentation and modeling capabilities improve (Krahenbuhl et al, 2011). This technique was meticulously applied over Prudhoe Bay, Alaska, for a period from 2003 to 2007 to confirm a microgravity signal to enable water flood sur-veillance in the giant field (Ferguson et al, 2008).…”

Using surface and borehole time‐lapse gravity to monitor CO2 in saline aquifers: a numerical feasibility study

“…Also, note that the density contrast within the plume varies smoothly and spans a wide range of values due to the smoothly varying CO 2 saturation profile considered in this study (Fig. ), which precludes the use of focussing or binary inversions, which are well‐suited to invert for density distributions having sharp density transitions between the studied object and the surrounding media.…”

“…leakage through a leakage pathway). Therefore, the gravity method cannot be considered as a ’stand‐alone’ technique and should be conducted in tandem with other techniques . For instance, this method could be conducted between two successive seismic surveys in order to monitor, at a moderate cost, the spatial evolution of the main bulk of the CO 2 plume over time, i.e., the main central portion of the plume as depicted in Fig.…”

“…Spatially correlated noise sources originating from hydrology and surface displacements are not included in the present study, and these would further add to the inversion error if not accounted for. 30 For instance, this method could be conducted between two successive seismic surveys in order to monitor, at a moderate cost, the spatial evolution of the main bulk of the CO 2 plume over time, i.e., the main central portion of the plume as depicted in Fig. 2 .…”