--> Abstract: Effects of Sandstone Composition and Diagenesis on Reservoir Quality, Tertiary-Pleistocene, Gulf Coast Region, by David K. Davies, William R. Almon; #90967 (1977).

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Abstract: Effects of Sandstone Composition and Diagenesis on Reservoir Quality, Tertiary-Pleistocene, Gulf Coast Region

David K. Davies, William R. Almon

The quality of sandstone reservoirs in the Tertiary-Pleistocene sequence of the Gulf Coast is affected by both original composition and diagenesis. Porosity and permeability are controlled by (1) original depositional matrix, (2) grain crushing, (3) solution and reprecipitation of carbonate shells, (4) authigenic clay pore linings, (5) authigenic clay and carbonate pore fills, and (6) development of secondary porosity. Factors 1 through 4 act as important controls on reservoir quality in Pliocene-Pleistocene offshore reservoirs. All six factors combine to control reservoir quality in pre-Pliocene sandstones.

The presence of diagenetic minerals in a sandstone can totally alter the electric-log response. A log may indicate that a sandstone is water saturated, and yet the well may produce water-free oil. This is commonly a result of the presence of authigenic clay pore linings which bind water to the framework grains. Thus, hydrocarbons may be underestimated when a sandstone contains only a few percent authigenic clays. The acid or freshwater sensitivity of a sandstone also may be controlled by the diagenetic minerals. Diagenetic pore linings receive the greatest exposure to drilling, treatment, and completion fluids, and greatly affect reservoir quality. A knowledge of both sandstone composition and diagenesis is essential in defining optimum exploration strategies, as well as for drilling nd stimulation treatments.

AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas