Method for selectively plugging subterranean formations with pol

Details Method for selectively plugging subterranean formations with pol Method for selectively plugging subterranean formations with pol

1987-10-07

1988-09-27

Suchfield, George A.

Wells

Processes

Distinct, separate injection and producing wells

166271, 166281, 166292, E21B 33138, E21B 4327

Patent

active

047734833

ABSTRACT:
The relatively highly permeable zones of a subterranean oil containing formation having a neutral to alkaline pH are selectively plugged by initially injecting an aqueous acid solution into the relatively highly permeable zones that lowers the pH of these zones to about 6 or less. Thereafter, an aqueous polysulfide solution is injected into the formation that preferentially enters the relatively highly permeable zones and allowed to disproportionate under the pH conditions within the relatively highly permeable zones to form a precipitate of elemental sulfur in situ which plugs the relatively highly permeable zones in the formation. Thereafter, improved sweep efficiency is realized in displacing oil from the lesser permeable zones. If the natural pH of the relatively highly permeable zones in the formation is about 6 or less, the initial treatment with the aqueous acid solution is unnecessary.

REFERENCES:
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patent: 3004599 (1961-10-01), Goodwin et al.
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patent: 3376931 (1968-04-01), Messenger
patent: 3428129 (1969-02-01), Cook
patent: 3438439 (1969-04-01), Froning
patent: 3841405 (1974-10-01), Moote et al.
patent: 4438976 (1984-03-01), Baughman
"Polysulfide Stops FCCU Corrosion": by E. F. Ehmke, HYDROCARBON PROCESSING, Jul. 1981, pp. 149-155.

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