Inversion of surface and borehole gravity with thresholding and density constraints

Minimum-structure inversion has been widely used in both hydrocarbon and mineral exploration for decades. However, models obtained with this method typically exhibit smooth variation of physical properties and smeared-out boundaries, and may not give detailed information about the target being investigated. In this paper we present a constrained joint inversion of surface and borehole gravity to increase the resolution of gravity inversion. We show that inversion of surface and borehole gravity with thresholding can help estimate the dip of the density anomalies to well. We then incorporate this dip information, as well as density constraints based on measurements of drilhole samples, into the inversion. We demonstrate that such a joint inversion approach can significangly improve the resolution of density inversion.