Browsing by Subject "Woodbine Group"

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Reservoir characterization of the Upper Cretaceous Woodbine Group in Northeast East Texas Field, Texas
(2012-05) Dokur, Merve; Fisher, W. L. (William Lawrence), 1932-; Hentz, Tucker F.; Steel, Ronald J.
East Texas field, a giant U.S. oil-field, produced 5.42 billion stock-tank barrels from discovery in 1930 through mid-2007. The lower part of the siliciclastic Upper Cretaceous Woodbine Group is reservoir rock, and almost all production comes from the upper unit, the operator-termed Main sand. The field could produce 70 million stock-tank barrels (MMSTB) using current strategies, whereas 410 MMSTB of remaining reserves from the Stringer zone (lower unit), along with bypassed pay in both units and unswept oil, is possible. These favorable statistics have increased interest in reservoir characterization of the Woodbine, especially the Stringer zone. This study delineates sandstone geometry and interprets reservoir facies and heterogeneity of the Stringer zone and Main sand in northeast East Texas field. Additional objectives are to define key chronostratigraphic surfaces, such as flooding surfaces and unconformities, and to establish a realistic depositional model for the reservoir succession. To achieve these objectives, well log analysis, core description, and net-sandstone mapping of the Stringer zone and Main sand were conducted. According to sequence-stratigraphic and depositional-system analysis, the Woodbine Group is divided into two genetically unrelated units: (1) the highstand deltaic Stringer zone and (2) the lowstand incised-valley-fill Main sand. Principal reservoir units are Stringer 1 and Stringer 2 sands within the Stringer zone and the Main sand. Stringer 2, best developed in the southwest study area, is the most promising reservoir unit for new production. Well deepening and water-flooding in this more continuous and thicker sand are proposed to increase production in East Texas field.
Sequence stratigraphy and depositional systems in the Upper Cretaceous (Cenomanian) Woodbine Group, Anderson and Cherokee Counties, Texas
(2016-08) Krueworramunee, Kullamard; Fisher, W. L. (William Lawrence), 1932-; Ambrose, William A.; Mohrig, David
The Woodbine Group of the East Texas Basin has attracted considerable interest because of its remaining petroleum resource in the deeper Woodbine pay. Recent estimate of the remaining petroleum resources in the East Texas field is approximately 1.58 billion stock tank barrels (BSTB) (Wang et al., 2008). However, expected ultimate recovery is limited by reservoir compartmentalization controlled by a complex stratigraphic framework. The purpose of this study is to define depositional systems and construct the stratigraphic framework of the Woodbine Group in Anderson and Cherokee Counties to provide the geologic context for characterizing remaining reserves. This study integrates core data and log data from closely spaced wireline logs (~1000 wells), using a chronostratigraphic method, to define sequence stratigraphic units. The stratigraphic framework of the Woodbine succession in the study area is composed of a maximum of 14 cycles in the basin axis, decreasing to a minimum of 3 cycles eastward to the Sabine Uplift and a minimum of 6 cycles westward to the out crop belt. The Woodbine succession is overlain by impermeable deposits of the Eagle Ford Shale and the Austin chalk as hydrocarbon seals. The complexity and heterogeneity of sandstone bodies in the Woodbine Group are largely controlled by depositional origin. Woodbine highstand and lowstand sequences display great variations in the depositional systems. The highstand deposits are composed mostly of fluvial dominated delta deposits that consist of distributary-channel, crevasse-splay, and delta-front deposits. Gamma-ray and spontaneous potential responses for these highstand deposits are upward-coarsening and serrate. In contrast, Woodbine lowstand deposits are mainly composed of coarse-grained sandstones of incised valley fills, reflecting relative base-level fall. These lowstand deposits, truncate older highstand deposits and are inferred from planar-based and blocky serrate log responses. Furthermore, highstand and lowstand deposits are overlain by transgressive deposits. These transgressive deposits are characterized by upward-fining log response, reflecting relative base-level rise. Correlation of sequence stratigraphic surfaces, sandstone-body stacking patterns and reservoir complexity inferred from gross-sandstone maps can lead to new exploration targets in the Woodbine Group in the southern part of the East Texas Basin.