Woodbine Regional Study

The Woodbine of upper Cretaceous Age has been one of the most prolific oil and gas targets in the East Texas Basin. Exploration for Woodbine production in east Texas has been intensive since the first discovery was made at Mexia in October of 1920. The majority of Woodbine exploration and production has been confined to an area north of the Angelina-Caldwell flexure and the Edwards reef trend. Production from the Woodbine interval in this area has been from depths of between 3,000 to 6,000 feet. Recent discoveries of Woodbine gas, however, south of the Angelina-Caldwell flexure have extended the area of exploration. The Woodbine in this area is encountered at depths of 10,000 to greater than 15,000 feet. For purposes of this study, these two areas are referred to as the shallow and deep Woodbine of East Texas. The Late Cretaceous continental shelf and the beginning of the continental slope in east Texas are marked by the Angelina-Caldwell flexure and Edwards reef trend. The shallow Woodbine, therefore, represents deposition north of the shelf edge and the deep Woodbine represents deposition south of the shelf edge. This regional geologic study encompasses both areas of Woodbine deposition.

Exploring for Woodbine production within the East Texas Basin is complex. Depositionally, the formation is complex. The sand bodies that form reservoirs are erratically distributed in the section and represent various environments from fluvial to marine. No single, simple, depositional model can be used for exploring for Woodbine traps. A regional study of the depositional environment for Woodbine clastics within the East Texas Basin provides valuable information to the petroleum explorationists.

Core Laboratories strongly feels that oil companies will benefit in both an exploration and production sense by acquiring the Reservoir Evaluation of the Woodbine Formation Study. A study which geologically and petrophysically characterizes conventional cores and cuttings from forty-four (44) wells will enable members to:

• Select drilling fluids which are compatible with the reservoir conditions and minimize formation damage
• Define reservoirs units within the Woodbine based on depositional patterns, reservoir geometries, and reservoir continuity
• Define the regional distribution of various types of sandstone mineral, textural, and pore space properties in Woodbine reservoir rocks, particularly those associated with diagenetic clay phases
• Properly locate development wells within a Woodbine field
• Effectively interpret hydrocarbon-bearing Woodbine sandstones which appear “wet” on electric logs due to the presence of diagenetic clays in the pore network
• Design proper well stimulation and/or fracturing treatments to efficiently produce hydrocarbons from Woodbine reservoirs
• Aid in lease acquisition and in overall exploration and exploitation efforts for Woodbine wells.
• Assist in the selection of the number and location of injectors, composition of enhanced recovery fluids, and the treatment of injection and production wells for Enhanced Recovery programs within Woodbine fields

The study contains individual well reports from all forty-four (44) wells and a final report which summarizes the study results.

• Forty-four (44) wells
• Conventional core and drill cuttings