Stylolite porosity in carbonate reservoirs
Stylolite porosity in carbonate reservoirs Despite the common presence of stylolites in carbonate reservoirs, the influence of stylolites on porosity has not been investigated systematically. Because stylolites result from pressure solution, stylolitization is inferred to have been an important source of calcite. Hence, the prevalent views are: (1) porosity decreases toward stylolites, (2) stylolites are permeability barriers, and (3) stylolites carbonate rocks are porous, and the distribution of some porosity is genetically related to stylolites. Most importantly, and contrary to prevalent views, porosity may increase toward stylolites. Examples of stylolite porosity exist in the Paradox, Delaware, and Williston basins. Several types of stylolite-associated porosity are discernible: open stylolite seams, fabric-selective megaporosity halos, vugs, microporosity halos, fractures, and crystal molds. Stylolite porosity results from post-stylolitization marginal dissolution, where stylolite seams have served as conduits for CaCO/sub 3/-undersaturated basinal fluids. This interpretation implies that stylolites may be reopened (probably by partial uplift and unloading) during mesodiagenesis. Subsequently, open stylolites provide conduits for diagenetic fluids and hydrocarbons through otherwise impermeable strata. Stylolite porosity may significantly enhance reservoir quality. The flow of CaCO/sub 3/-undersaturated fluids along stylolites and marginal stylolite dissolution have been duplicated experimentally at confining pressures simulating up to 15,000 ft of burial.
Enter terms in the toolbar above to search the full text of this document for pages containing specific keywords.