| Description |
Gravity and gravity gradiometry surveys have been widely used in mining and petroleum exploration. Interest in borehole gravity measurements has grown because they can help to detect deep targets for a relatively low cost. The best way to obtain a 3D density distribution is by a joint interpretation of the surface and borehole gravity data, which is a very challenging problem. The 3D inversion would be a method of choice for the quantitative interpretation of gravity and gravity gradiometry data. However, the rigorous inversion is a complicated and very time-consuming procedure, ant it is dependent on the a priori model and constraints used. In this dissertation, I show that a joint iterative migration of the surface and borehole gravity and gravity gradiometry data can be an effective instrument of imaging the subsurface density distribution. I present the results of the new development in the joint migration of the surface and borehole gravity and gravity gradiometry data. In this dissertation, I also consider an application of the developed approach to geophysical monitoring of carbon dioxide (CO2) injections in a deep reservoir, which has become an important component of carbon capture and storage (CCS) projects. Until recently, the seismic method was the dominant technique used for reservoir monitoring. The cost of seismic surveys, however, makes this method prohibitive in monitoring sequestration projects where there is not any direct profit available. Moreover, some environments present challenges for seismic acquisition, e.g., in urban areas. In this dissertation, I present a feasibility study of gravity gradiometry monitoring of CO2 iv sequestration in a deep reservoir using a novel approach involving both borehole and surface measurements. The interpretation of the observed data is based on joint iterative migration of the surface and borehole data. The advantage of this method is that the surface data provide a good estimate of the horizontal extent of the injection zone, while the borehole data control the depth of the target, which increases the sensitivity and resolution of the method. We illustrate the effectiveness of the gravity gradiometry method by computer simulating CO2 injection monitoring in the Kevin Dome sequestration site in Montana, USA. |
