LUO, MING, MARK R. BAKER and DIANE I. DOSER, Department of Geological Sciences, University of Texas at El Paso, El Paso, TX

ABSTRACT: A Quantitative Modeling of the Overpressure System in the Eastern Delaware Basin, West Texas and Southern New Mexico.

An overpressure system occurs in the eastern Delaware basin, covering at least six Texas and New Mexico counties. Quantitative modeling of overpressure in one-dimension has been conducted in the War-Wink gas field where pressure variations are well documented. Compared with previous overpressure models, this study reconstructs the paleopressure history of the sedimentary basin by integrating vertical principal stress, geothermal temperature, geological time, heat transfer, variation of sedimentation, porosity evolution, clay dehydration, and hydrocarbon generation. This overpressure simulation predicts the time and depth of overpressuring based on the regional geology and mechanism of overpressure generation and development. The modeling suggests that significant overpressuring in the eastern Delaware basin did not occur until the end of Permian time and that the full development of the overpressure system was during Mesozoic and Cenozoic time. Contributions to overpressuring from different causes are simulated in the modeling process. The present overpressure system seems to be a product of disequilibrium compaction, clay dehydration, hydrocarbon maturation, and thermal expansion. The permeability simulation indicates that the seals of the overpressure system are controlled by a sharp decrease in permeability to an extremely low level both above and below the system. On the other hand, permeability within the overpressure system is abnormally high, possibly due to an increase of secondary porosity and the occurrence of fractures. The simulated geothermal temperature nd conductivity appear to support the idea that a decrease of thermal conductivity of overpressured sequences may reinforce overpressuring.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.