Browsing by Subject "Fort Worth Basin"
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Item Geologic setting and reservoir characterization of Barnett Formation in southeast Fort Worth Basin, central Texas(2014-08) Liu, Xufeng; Fisher, W. L. (William Lawrence), 1932-; Loucks, R. G.The Mississippian Barnett Formation is a prolific shale-gas reservoir that was deposited in the Fort Worth Basin, Texas. Many previous studies of the Barnett Formation have been conducted in the main production area; few studies have been made of the Barnett Formation in the southern part of the basin, which is a less productive area. In the present research, several cores from the Barnett Formation in Hamilton County, southeast Fort Worth Basin, are studied in detail. Two vertical, continuous cores from Hamilton County, Texas, were studied to delineate the depositional setting, lithofacies, pore types, and reservoir quality of the Barnett Formation in the area. Five lithofacies were defined by analysis of the two cores: (1) laminated clay-rich silty and skeletal peloidal siliceous mudstone; 2) laminated skeletal silty peloidal siliceous mudstone; 3) nonlaminated silty peloidal calcareous mudstone; 4) laminated and nonlaminated skeletal calcareous mudstone; and 5) skeletal phosphatic packstone to grainstone. As indicated from this study, the dominant organic matter type is a mixture of Type II (major) and Type III (minor) kerogen having a mean TOC content of approximately 4%. Analysis of Rock Eval data shows that most of the interval is within the oil window; calculated Ro is approximately 0.9%. Organic geochemistry shows that the hydrocarbon generation potential of the abundant oil-prone kerogen was excellent. Mineralogical analysis reveals that the two types of siliceous mudstone, which are similar in composition to the siliceous mudstone in the main producing area in the northern Fort Worth Basin, are good for hydraulic fracturing and production, but they are also limited by their marginal thickness. Organic matter pores, which are the dominant pore types in these two cores, are consistent with pore types found in currently producing wells in the Newark East Field. This research also suggests that the deposition of Barnett Formation was controlled largely by basinal geometry, suspension settling, and slope-originated gravity-flow events. Skeletal deposits and carbonate-silt starved ripples suggest gravity-flow deposits and bottom-current reworking during deposition. Redox-sensitive elements and degree of pyritization both indicate anoxic/euxinic conditions during the deposition of the Barnett Formation.Item Lithofacies, depositional systems, and depositional models of the Mississippian Barnett Formation in the southern Fort Worth Basin(2016-08) Redmond, Lauren Patricia; Loucks, R. G.; Rowe, Harry; Kerans, Charles; Fisher, WilliamThe Barnett Formation in the Llano Uplift region of the southern Fort Worth Basin of north-central Texas is an Osagean-Chesterian age siliciclastic mudrock whose deposition was influenced by the structurally stable Llano Uplift, topographic variabilities, and a long-term, second-order sea-level rise. Pervious work has mostly focused on the producing northern portion of the basin. The present study uses a group of 29 cores to: (1) characterize the Barnett lithofacies, (2) define the depositional setting of each lithofacies and develop a coherent depositional model, (3) identify stacking patterns and correlative surfaces, and (4) establish a viable sequence stratigraphic framework for the succession. On the basis of core data, the Barnett strata are interpreted to have been deposited in a basinal setting, below storm-weather wave-base, under predominantly anoxic bottom waters. The analysis of core and thin sections revealed four dominant lithofacies: (1) laminated siliceous mudstone, (2) laminated calcareous siliceous mudstone, (3) skeletal packstone, and (4) phosphatic packstone and grainstone. Facies stacking patterns were correlated using phosphatic packstone facies as regional marker beds. These beds coincide with changes in clay-mineral abundances, revealed by chemostratigraphic data, and their occurrences were used to subdivide the Barnett strata into lower, middle, and upper units. The lower Barnett is characterized by cyclic sedimentation of extrabasinal clays and has the greatest thickness variability related to accumulation of the calcareous siliceous mudstone facies in graben structures. The middle Barnett is characterized by an increase in extrabasinal clay abundance compared to the lower Barnett, and the upper Barnett is characterized by a decrease in the extrabasinal clay abundance compared to the lower and middle Barnett. The phosphatic packstone facies is sourced from the outer shelf/upper slope of the adjacent Chappel Shelf and is interpreted to represent cycle tops within the aggradational stacking pattern that characterized sediment accumulation style during the second-order sea-level rise that occurred throughout Barnett deposition. The findings contribute to the understanding of the stratal architecture and depositional history of the Barnett deep-water mudrocks and are used to refine the lithofacies variability of the Barnett Formation.