Abstract

The West Jordan unit, in Jordan field, is located along the eastern margin of the Central Basin platform in Ector and Crane Counties, Texas, and produces from a 550-foot interval within the San Andres Formation. A reservoir characterization study of the San Andres Formation was initiated in 1997 to gain a better understanding of flow properties in the reservoir. Cross plot analysis shows no correlation between porosity to permeability for most pore types. Therefore, a permeability transform derived from a single porosity-permeability regression line would be fraught with uncertainties. Although intercrystalline and well-developed fenestral pores have a higher correlation coefficient than other pore types, the correlation within these pore types is weak at best.

The method used in this study to estimate permeability is a modification of that proposed by Lucia (1999). The model integrates the distribution of petrophysical rock-fabric into a chronostratigraphic-geological model along with engineering and production data. Lucia (1999) has demonstrated a method for linking carbonate rock types to petrophysical properties such as porosity, permeability, and water saturation and has derived a permeability transform that incorporates the flow properties characteristic of rock fabric pore types. A modification of this method was applied to cored wells within the unit in order to measure its accuracy within cycle boundaries and then applied to all wells with petrophysically derived porosity data. The method was found to be effective even with the multiple vintages of old-style neutron-count logs that make up the bulk of porosity data for the unit. The use of this permeability transform method is believed to have been successful because of its application in a well-defined, three-dimensional chronostratigraphic-geologic model where pore types have been carefully defined in facies tracts within individual cycles. The objective of this paper is to present a general overview of the methodology and application of this permeability transform within the West Jordan unit.