EVALUATING DIAGENETIC CHANGES AFFECTING CARBON DIOXIDE STORAGE POTENTIAL IN THE CHERRY CANYON FORMATION OF THE FORD GERALDINE FIELD, TEXAS

The 4,500 ft thick (1,375 m) Delaware Mountain Group is an important reservoir in the Permian Basin for potential geologic storage of carbon dioxide. These Guadalupian age (~270 Ma) deep-water deposits contain a mixture of arkosic sand, silt, and detrital skeletal debris deposited during sea level lowstands in the Delaware sub-basin. The Cherry Canyon Formation of the Delaware Mountain Group has porosities up to 30% and permeability between 0.04 mD to 73 mD. Intragranular porosity in the Cherry Canyon sandstone is largely filled with silica cements or with authigenic clay cements. There are also irregular spaced zones tightly cemented with calcite, ranging from less than an inch (1.5 cm) up to several inches (~ 27cm) thick. Calcite cements appear to be linked to the development of secondary porosity from the alteration of skeletal-rich debris flows and are markedly different from the surrounding silica and clay cemented sand and silt reservoir intervals. Understanding the distribution of the calcite cemented non-reservoir intervals is important for our ability to characterize the storage capacity of the Cherry Canyon Formation, because the distribution of cements influences fluid flow paths, reduces reservoir porosity, and causes reservoir compartmentalization.

Here, two cores through the lower Cherry Canyon Formation in the Ford Geraldine Field along the Reeves/Culberson County line, Texas, the 6 Ramsey #26 and Continental TXL 31-3, are used to evaluate the mineral distribution, textural relationships, and cementing phases in these sands. Specifically, the distribution and composition of silica, authigenic clays, and carbonate cements is evaluated with traditional petrographic techniques, cathodoluminescence petrography, and scanning election microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). Preliminary observations show the earliest cements were quartz overgrowths and that calcite cements and authigenic clays were likely formed by alteration of skeletal debris and feldspar hydrolysis. This work will provide key constraints on the mineralogy and distribution of cementing phases in the Cherry Canyon Formation in the Ford Geraldine field that can be used to inform reservoir models for potential geologic sequestration of carbon dioxide.