Hydrogeochemistry and water management in a Venezuelan heavy oil reservoir: Evidence from the Carabobo field

To understand the origin and evolution of formation waters in the Carabobo oil reservoirs, a hydrogeochemical characterization was conducted on 73 water samples collected from production boreholes, rivers, aquifers, and drilling mud. Since the oil boreholes were active, the local effects on them were considered beforehand, to diagnose water-related problems. The primary objective of this study was to demonstrate how data from a regional investigation can be used to improve the understanding of local water-related issues and optimize oil production management, while simultaneously refining the outcomes of the regional assessment. At the local scale, chemical and isotopic analyses revealed water intrusion from an upper stratum in one borehole, pipe corrosion in another, and methanogenesis in most boreholes. Notably, a deuterium enrichment in water (exceeding +10‰ δD relative to the meteoric water line) resulting from methanogenic activity under isolated conditions was documented. This study demonstrates the potential of hydrogeochemistry as a tool for systematically characterizing oilfield waters. It reveals how water interacts with porous media, organic matter, and microorganisms, as evidenced by their chemical and isotope compositions. This information is useful for optimizing oil reservoir management and promoting the oil production.