--> Abstract: Geologic Heterogeneities of Interbedded Permian Siltstones, East Ford Field, West Texas, by Anierobi Louis Ekweogwu; #90089 (2009)

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Geologic Heterogeneities of Interbedded Permian Siltstones, East Ford Field, West Texas

Anierobi Louis Ekweogwu
Sul Ross State University, Alpine, Texas

To better support an exploration effort, assessment results should fully represent the internal variations within the play. The East Ford field in Reeves County, Texas produces from Ramsey sandstone in the Upper Bell Canyon Formation. Field production has increased from 30 to more than 185 BOPD. This recovery has been improved by the CO2 flood, but not as much as expected.

The goal of the East Ford Field project is to (1) Study key reservoir characteristics from the subsurface cores with the aim of understanding, evaluating and possibly outsmart any suspected geologic heterogeneities. (2) Create readily accessible digital format information that can be widely disseminated for future studies. The ultimate aim of reservoir description is the characterization of reservoir heterogeneities in accordance with the building of a proper geological model. The depositional model approach was from the Bell Canyon outcrops and subsurface data of four wells from the East Ford field. The cores from the wells are from the core library at CEED, Midland, Texas. Core data provides positive evidence of hydrocarbon presence, storage capacity for reservoir fluids (porosity), and flow capacity (permeability). Accurate measuring of the permeability and porosity as well as the specific storage from core samples is especially important to explore the fluid percolation process. Because of low permeability of siltstones, limited cross flow of fluids will occur between sandstones separated by siltstone. And heavily calcite cemented sandstones typically have moderate to poor connectivity.

At its basic level, reservoir properties such as the permeability and porosity are the controlling factor in the production history for this field. The recognition of pay zones and the usefulness of using current technology on older core samples is the desired end result. As reservoir characterization efforts increase with the ever-changing needs of the world oil market, the need for multidisciplinary approach to reservoir description that emphasizes more quantifiable results increases.

This project is being designed to provide basis for planning new costeffective data acquisition strategies, and integration of programs to systematically reduce exploration risk for optimum production.

The cores are interpreted as having been deposited in basin-floor setting by a system of leveed channels having attached lobes and overbank splays. Interbedded siltstones are probably the most important cause of heterogeneity in the Ramsey reservoir. Because of the low permeability and porosity values of siltstones for some weakly cemented siltstone, limited crossflow of fluids occurs between siltstones and sandstones. Current technology applied for the assessment of these heterogeneities is surface laboratory measurement for high resolution and routine core analysis studies.

AAPG Search and Discovery Article #90089©2009 AAPG Southwest Section Meeting, Midland, Texas, April 26-29, 2009