Mobil Oil Corporation

Eleanor R Fieler

Alfred R Jennings, Jr

James M Paul

John L Hen

A method for placement of a long life scale inhibitor into a formation where variable density scale inhibitors are utilized. A substantially low density non-reactive fluid is loaded into an interval of the formation to be treated. Afterwards, a high density first stage scale inhibitor is injected into the interval. Thereafter, a low density spacer fluid is injected into the interval being treated. Next, a second stage high density scale inhibitor having a density lower than the first stage inhibitor is injected into said interval. Subsequently, a low density spacer is injected into the interval. Volume increments are repeatedly injected with decreasing fluid densities until a desired zone has been treated. The entire treatment is then overflushed with an inert high density fluid. Use of this method allows even inhibitor distribution in intervals of a formation with permeability variations thereby preventing scale build-up.

Method for effective placement of a long life scale inhibitor

A method to improve the efficiency of scale dissolution in a formation containing multiple productive intervals where variable density liquids are utilized. Initially, a liquid composition sufficient to solubilize an alkaline-earth metal sulfate scale deposit is directed into a wellbore thereby contacting scale in one productive interval of the formation. Thereafter, a second scale solubilizing liquid having a density of about 0.1 wt % less than the first liquid is directed into the wellbore thereby contacting additional perforations and a higher interval. These scale solubilizing liquids with varying densities are allowed to remain in contact with perforations and productive intervals communicating therewith for a time sufficient to solubilize the scale deposit thereby efficiently removing said scale deposit from perforations and productive intervals at two different levels.

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Dallas, TX, United States of America

Eleanor R Fieler