The Control of Provenance from Reservoir Quality and Rock Properties of Clastic Wilcox and Frio Sediments in the Gulf of Mexico
Tobi Kosanke, Neil Braunsdorf, and Tom Taylor
Shell International E and P, Houston, TX
Provenance impacts both the mechanical properties and chemical diagenetic processes that affect porosity and permeability of reservoir rocks. We have compiled composition and textural data for Wilcox and Frio sands in the northern Gulf of Mexico to determine their provenance and its impact on reservoir quality. We determined that the reservoir quality of any particular reservoir depends on its age and location. The different positions of the sediment delivery systems in the Wilcox and Frio resulted in a marked change in sand composition between Wilcox and Frio times, with contrasting lateral compositional trends from west to east. The most prevalent diagenetic effect in the relatively quartz-rich sandstones is porosity reduction by compaction and quartz cementation. The more lithic-rich sands, however, experience reduction of reservoir quality due to compaction of ductile grains, but less quartz cementation and greater secondary porosity. These lithic sands may also contain grain-coating clay that inhibits quartz cementation. The impact of provenance on both the mechanical properties and chemical diagenetic processes of these different sand compositions may result in very different acoustic properties of these reservoirs in the subsurface.
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