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Abstract

Recent advances in biotechnology have led to the identification and isolation of polymer-specific enzymes. This new technology has been incorporated in the development of improved damage removal systems. The polymer specific reactivity of the new systems provides environmentally safe polymer degradation without causing damage to the formation or tubular goods.

Polymer specific systems have been developed for removal of damage caused by polymers such as cellulose, guar, and starch. The treatments can be applied over a wide range of downhole conditions to polymeric damage resulting from fracturing, gravel packing, or workover operations.

Fracture conductivity and core flow evaluations have shown that multi-fold improvements in permeability are achieved with the new systems. Damaged wells treated with the new systems have experienced up to three-fold improvement in well productivity. A detailed study and analysis of laboratory and field data are presented.

Introduction

Polymeric damage to proppant pack and formation permeability can significantly decrease well production. The damage, in many cases, is due to insufficient degradation of drilling, completion, or stimulation fluids and the dynamically formed filter cake on the formation face. A filter cake is a dense, practically insoluble concentration of polymer deposited on the fracture face. The presence of filter cake may impede flow, dramatically reducing the productivity of the well. Several studies have shown that the concentration of polysaccharides within a filter cake can range from about 10 to greater than 25 times the surface polysaccharide concentration of the stimulation treatment. For instance, if a fracture treatment fluid contained an original polymer concentration of 40 pounds per thousand pounds (ppt), the filter-cake concentration could easily be 500 ppt. The obvious goal, therefore, exists to reduce or remove the polymeric damage in order to obtain the optimum productivity the stimulation treatment was intended to provide.

STATEMENT OF THE PROBLEM

Various methods have been used to remove damage in an effort to increase well productivity. Several previous studies describe the application of conventional cleanup treatments.

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