WELL TREATMENT TECHNIQUES FOR RESTORING YIELD AND REDUCING SAND PUMPING*

INTRODUCTION

Many wells in Colorado and elsewhere experience continuing reduction in yield throughout their service life. Sand pumping often creates expensive operation and maintenance problems. In the past, loss of well yield and/or sand pumping was tolerated until continued operation of the well was no longer economical, and the well was then redrilled.

Recent advances in well treatment and rehabilitation technologies offer an alternative to redrilling problem wells. These technologies include Sonar-Jetting, treatment using specialized tools for placing and removing chemicals, and installation of Aquastream units within the existing well.

This paper will discuss the factors which contribute to well failure, identify alternative methods for well treatment and rehabilitation, and present several case histories where innovative methods have been used in Colorado to restore well yields and reduce sand pumping.

TYPES OF WELL PROBLEMS

The performance of a well often declines during the life of the well. The decline may be due to one or more of the following factors:

1. Lowering of the static water level.
2. Inefficient pumping caused by worn, corroded, or plugged pumps;
3. Blockage of the well screen and gravel pack by mud, sand, and silt;
4. Deposits of encrustation, corrosion products, and microorganism growths at the well screen, at the aquifer face, and/or in the pump; and,
5. Failure of the well casing and/or screen resulting in s and pumpage.