How Important is the Impact of Burial Corrosion on Carbonate Reservoirs? Learning's from Case Studies
Burial corrosion has been put forward since the early 90's, as a relevant diagenetic process controlling reservoir properties. However, more recently, the occurrence and/or relevance of burial corrosion has been questioned. Certainly, simple mass balance calculations may suggest that maintaining corrosion on a carbonate system can be difficult: (1) assuming closed chemical conditions, (2) using simple reactions and (3) not reproducing the actual physico-chemical conditions prevailing in the deep burial realm. The petrographic observations and geochemical data obtained in a large number of studied carbonate reservoirs suggest that burial corrosion plays a relevant role in modifying the rock properties, including enhancement and/or redistribution of porosity, and more importantly, increasing permeability. This contribution will summarize petrographic and geochemical information from several carbonate reservoirs where late burial corrosion has been important in the generation and distribution of present-day reservoir properties. Geochemical markers and fluid inclusion information confirm that corrosion occurred in the burial realm for the studied cases and provide indirect information about the chemistry of the corrosive fluids. Burial corrosion in the studied cases was caused by: mixing of formation brines with deep-seated brines with different pressure, temperature and chemistry than those of the formation fluids, mixing of formation brines with charge-related fluids, and/or directly by TSR (e.g. anhydrite dissolution) or indirectly by the corrosive fluids generated by TSR. Although in all these cases corrosion clearly occurred during burial, the extent and impact on (i) the actual rock properties and (ii) their distribution varies on a case by case basis.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013