ABSTRACT

Alcohol when added to stimulation fluids will reduce or eliminate waterblocking following these treatments. Although waterblocking can occur in clean, well consolidated sandstone, it is more likely to occur with other forms of damage such as particle blocks or rock wettability changes. Waterblocking is most severe in heterogeneous formations particularly where high permeability variations are in series such as in crossbedded sediments. Alcohol has been successfully used in waterblock removal, matrix acidizing, and hydraulic fracturing. Properties of alcoholic fluids and detection of heterogeneity are discussed. Guidelines for selecting the best alcoholic treatment are presented.

INTRODUCTION

Aqueous stimulation fluids containing alcohol have proven to be highly successful in stimulating gas production from problem wells in sandstone formations. The primary advantage of alcohol is to obtain better and more rapid clean up. It is most useful in gas producing formations, particularly those with a high clay content.

Many stimulation treatments in sandstone which would otherwise be quite successful are spoiled by a very slow water clean-up. This clean-up problem is often a result of water block in the critical matrix surrounding the wellbore. In a gas well, about one-half the total pressure drop in the formation takes place within 15 ft surrounding the wellbore. The addition of alcohol to the aqueous fluid can often prevent this water blocking problem.

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