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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 288

Last Page: 289

Title: Reservoir Description Applied to Iatan East Howard Field, Mitchell County, Texas: ABSTRACT

Author(s): Stephen M. Mitchell

Article Type: Meeting abstract


A reservoir description has been completed to help improve recovery over Mobil Producing Texas and New Mexico's leases in the Iatan East Howard field in Mitchell County, Texas. The following 5 phases of study have been used: core description, log analysis, stratigraphy, mapping, and follow-up.

Two 850-ft cores were used to study depositional environment and diagenetic history. Clear Fork (Permian Leonardian) pay is characterized by thin, discontinuous porosity zones cut by vertical fractures. Porosity development is controlled by facies zonation from a tidal flat similar to that on Andros Island today. Porosity developed in carbonate-sand accumulations along tidal channels that meander and bifurcate across the flat. Thickness and continuity increase northwestward toward the basin. Six major zones of transgressive channel belt sediments separated by regressive supratidal marsh sediments were identified in the upper Clear Fork.

Digitized logs were analyzed and log analysis was accepted where porosity matched whole-core porosity measurements. Histograms of log response were used to normalize uncored wells to cored wells for equivalent results.

Stratigraphy was studied by cross sections of each zone. Facies-biased contouring was used to map reservoir parameters. Pay thickness was mapped using 2 porosity cutoffs with the higher identifying the best reservoir. Maps were digitized and used to calculate the original oil in place. The fracture orientation was recognized as N60°E from injection-water breakthrough, water sampling, and water-oil ratio mapping. Injectors will be placed along this trend perpendicular to porosity trends. Follow-up with reservoir engineering will continue with comparisons of mapped

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volume versus production histories and will influence pattern alignment and well spacing.

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Copyright 1997 American Association of Petroleum Geologists