--> Abstract: Differential Flow Rates of Petroleum and Water in Fine-Grained Sediments, by C. Clayton; #90990 (1993).

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CLAYTON, CHRIS, Kingston University, Kingston upon Thames, England

ABSTRACT: Differential Flow Rates of Petroleum and Water in Fine-Grained Sediments

During and after generation, petroleum migrates through fine-grained water-wet rocks into more permeable carrier beds. While the mechanics of this process are well established, little is known of the absolute rates of the process. In addition, it is known that in some areas (such as the deep-water Gulf of Mexico) oil is able to pass freely from the source rock through highly overpressured sediments in which the water is retained. This indicates that the apparent permeability to oil is one to two orders of magnitude greater than for water, too much to account for by the additional buoyancy of the oil or conventional relative permeability arguments. Part of the problem may be caused by the state of water in mudrocks, in which most of it is bound to clays and thus immobile. By assuming P iseuille flow of oil through the pore network of shales, it is shown that this indeed is the case. Modeled flow rates for oil are about two orders of magnitude faster than for water. This implies that only a small percentage of the water can be considered mobile, consistent with free/bound water ratios measured in the laboratory. Such calculations have important implications for estimating the time it takes for petroleum to charge distant reservoirs, and also for the longevity of oil and gas fields following seal failure.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.