Gravitational Drainage of Liquids from Unconsolidated Wilcox Sand

Abstract

A marked gravitational segregation of liquid has been observed to take placein a number of volumetric fields toward the later stages of their oil-producingperiods. This phenomenon has been pronounced in thick, highly permeable sandformations such as those of the Wilcox zone in Oklahoma City. This observationhas prompted considerable research directed toward the semiquantitativedetermination of the equilibrium saturation distribution of oil verticallythroughout a formation at final depletion. In this paper, data are alsopresented showing the transient distribution of liquid at different stages ofthe depletion period. Other experimental results show the effect of temperatureon the drainage rates of water, Wilcox crude oil, and a close-cut heptanefraction. Intermittent drainage of liquid produced saturation gradients thatmight well be expected from the flow theories involved. Yields of the variousliquids varied from 50 to 75 per cent of the original fluid content of thesand-packed (4 in. by 8 ft.) vertical tube. Introduction In certain volumetric oil fields the performance of the reservoir during thelatter part of its producing life is governed to a large extent by the downwardmovement of liquid due to the force of gravity. This is especially true offormations having thick or tilting beds of uniformly high permeability, free ofshale breaks. Leverett and Katz have presented original data and discussed thetheory relating to the capillary and gravitational forces acting on liquidscontained in a sand body. These investigators have pointed out the importanceof such studies in the estimation of future reserves as well as the originalfluid content of a reservoir. In this previous work, no data have been reported showing the history ofsaturation distributions during the drainage period. Since a knowledge of thesetransients is helpful in obtaining crude oil from such a reservoir, the authorshave obtained these data during this investigation. T.P. 1548

Improved efficiency of miscible CO2 floods and enhanced prospects for CO2 flooding heterogeneous reservoirs. Final report, April 17, 1991--May 31, 1997

“…Stahl et aZ. 252 conducted experiments to investigate behavior of free-fall gravity drainage of water and oil in an unconsolidated sand. Elkins et aLZ3 presented a simplified theory of regional drainage of oil from an upstructure to downstructure location due to gravity assuming zero capillary pressure gradient.…”

Specific yield - laboratory experiments showing the effect of time on column drainage

“…Drainage tests of unconsolidated Wilcox sand packed in pip<; columns 8 feet long and 2 or 4 inches in diameter were made by Stahl, Martin, and Huntington (1943). The columns were equipped with water jackets to maintain temperature control.…”

Utilization of Gravity Drainage Holes in Shallow Oil Recovery by Mining: Part II-A Conceptual Model for Drainage Hole Recovery

“…The mathematical theory of gravity drainage has been studied by several investigators (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Cardwell and Parsons (4) were the first to present a mathematical theory for estimating the rate of gravity drainage out of a sand column.…”

“…Cardwell and Parsons (4) were the first to present a mathematical theory for estimating the rate of gravity drainage out of a sand column. While capillary pressure gradients were excluded in their development, the 2 While capillary pressure gradients were excluded in their development, the 2 …”