Microgal gravity surveys have been used in the past for cavity detection in archeological sites such as in the Great Pyramid in Egypt, in karst topography and in mining areas. In this study we are applying this technology to an area of immediate interest to the petroleum industry. Borehole collapse in several wells in a Permian Basin field has propagated upward resulting in sinkholes that can be tens of meters deep, including several that have developed at the surface. Our study well shows signs of borehole collapse, but not a surface sinkhole. Seismic data suggest that a subsurface anomaly around the well is associated with this collapse. Gravity models indicate that borehole collapse should produce measurable gravity anomalies with amplitudes up to 1.4 mGal. A high-resolution gravity survey, °Gal level, was conducted over the area of the seismic anomaly. Gravity data along two profiles over a surface sinkhole to the north of the study well shows the expected gravity low over the sinkhole. However, the gridded gravity data over the study well and seismic anomaly does not show the expected gravity low, but rather shows an anomaly that appears to be sourced by a nearsurface density contrast. Subsurface collapse may have occurred followed by sedimentation filling the cavity.

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