Anomalous Brine Maps Yield Rapid Prospect Leads

ABSTRACT Sediments in predominantly sand-shale basins have abnormally high salinity at faulting and in the edgewater surrounding hydro-carbons. Anomalies can readily be seen when county-wide maps are prepared on brine concentration at the top of the hydrocarbon-bearing zone. Faulting tends to yield a linear zonation of strong brines, whereas hydrocarbon anomalies appear similar to structural contours. About 80% of Gulf Coast fields have anomalous salinity waters in edge wells which are no more than 2000 meters from commercial production. Productive wells have Redox Potential which reduces SP and prevents accurate analysis. Water composition is just one of the major variables which is used to evaluate a subsurface system. When combined with pressure gradients, temperature gradients, and Redox Potential data, the hydrocarbon environment may be located within 2000 meters and classified with a rough production probability index. Temperature gradients are strongly influenced by faulting and geopressure; whereas pressure anomalies correlate with the occurrence of gas and condensate production. For example, some counties in the Wilcox trend have most productive fields located over geopressure anomalies. The brine anomalies occur on the edge of the abnormal pressure gradient anomaly, which is opposite to the source of migration. End_of_Record - Last_Page 231-------