Hydrogeologic Description of Pressure Chambers and Application to Enhanced Oil and Gas Recovery - Final Technical Report

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Dutton, Alan R.

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This study aimed to identify geologic and hydrologic characteristics that delineate compartmentalized reservoirs in oil and gas fields, thereby enhancing our understanding of the hydrocarbon resource potential and facilitating improved recovery methods from such reservoirs. Compartmentalized reservoirs represent significant phenomena as they constitute major hydrocarbon reservoirs. The investigation focused on the Chocolate Bayou field in eastern Brazoria County on the upper Texas Gulf Coast. The methodology comprised three primary steps: (1) describing reservoir architecture using geologic data (structural and stratigraphic features, facies description), (2) characterizing hydrology (pressure distribution, reservoir depletion with production), and (3) assessing produced and unproduced reserves and undrained sections.

The concept of compartmentalized reservoirs in sedimentary basins was introduced by Amoco Oil Company in the 1970s. These reservoirs are hydrocarbon-bearing and are bounded by pressure seals, which are low-permeability envelopes surrounding the reservoirs. They can be conceptualized as "pressure chambers" with well-defined boundaries, typically exhibiting abnormally high pressures. Lateral seals, separating the abnormally pressured compartments from adjacent normally pressured ones, are characterized by vertical seals. Three types of seals are identified: basal, lateral, and top. Basal seals define the bottom of abnormally pressured compartments and usually follow a stratigraphic horizon, while lateral seals are typically associated with faults. Top planar seals may parallel or cut across time-stratigraphic boundaries and can develop in any lithology. Sedimentological, mechanical, and chemical factors contribute to compartmentalization.


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