Paleoenvironmental Reconstruction for Infill Drilling, White City Penn-South Carlsbad Field Areas, Eddy County, New Mexico: ABSTRACT

Abstract

The White City field and the southern part of the South Carlsbad field are located on the Northwest shelf in central Eddy County, approximately 15 mi south of Carlsbad and 4 mi east of White City, New Mexico. The field is a structural-stratigraphic reservoir producing predominately from a thick section of Pennsylvanian (Morrow, Atoka, Strawn) clastics and carbonates that were deposited on a shallow shelf edge. The older Morrowan clastics comprise most of the production in this area. Paleoenvironmental reconstruction and petrographic analyses characterize the lower half of the Morrowan as an overall prograding fluvial-deltaic sequence of channels, point bars, and channel mouth bars sourced from the northwest. This sequence trends toward the southeast, normal to depositional strike. The uppermost sand units are capped by shoal-water carbonate biograinstones. These strandling deposits are eventually overlain by a thick interval of transgressive Morrowan limestones. Although the study area involves a significant structural overprint, important stratigraphic traps are created in the sandstones by variations in cementation and depositional patterns. Because of the variable nature of deltaic deposition, the Morrow clastics were sliced into several correlatable genetic sand packages, and the lateral variability within each package was mapped using electric log signatures and assigningmore » the associated environmental interpretations. This process helped define the size, geometry, and orientation of sands at each interval, thus allowing the workers to establish reservoir limits and to understand the porosity and permeability behavior and facies changes within each slice. When these slices are vertically stacked, a three-dimensional attitude is realized for the entire reservoir, and detailed paleoenvironmental reconstruction is possible.« less