A Contribution to Hydrocarbons Exploration: Integration of the Gravity Method To Reduce Seismic Uncertainty in the Southern Desert Karst Region, Iraq

The study area is the Southern Desert (SD) of Iraq, known for its intensive karst features that are notoriously difficult to image subsurface using reflection seismic survey. Determining the subsurface karst terranes is of extreme importance in the exploration program and mitigation of the associated hazards. This contribution presents the gravity method as an auxiliary method with seismic reflection in detecting subsurface karst forms and determining their precise locations. Appropriate processing and interpretation of gravity data may be extremely helpful in resolving this issue and reducing seismic uncertainty, which is the principal goal of this work. The gravity field of the SD is decomposed into local and regional fields utilizing an upward continuation filter. The residual gravity maps are presented that might be used as an integrated tool in seismic data processing and interpretation, and in mitigating the hazards of the upcoming seismic survey. The near-surface negative anomalies in the SD are mostly linked with karst forms and near-surface density deficiencies. The decomposition is followed by estimating depths to the tops of geological structures using 1D radially averaged power spectrum analyses. A strong relationship between pre-existing exploration wells and positive residual gravity anomalies is found in the study area, indicating that these wells were drilled on structural highs of hydrocarbon interest. The available information on the total drilling depths for three wells shows encouraging results with the estimated depths utilizing the 1D radially averaged power spectrum method. Further, the results show that some wells have been drilled off the crest of the structures of interest. Therefore, this study provides a geophysical means of reconsidering the existing borehole results over relatively shallow structures.