THERMAL-STABILITY OF DRILLING-FLUIDS PREPARED FROM SAUDI PALYGORSKITE

High temperature in geothermal and deep wells is a major reason for the instability of drilling fluids. As a result of changes in their chemical and physical properties, problems such as gellation and formation damage can occur. Formation damage may result from high API fluid losses and reaction with formation fluid salts and hydroxides. In this paper the effect of elevated temperatures on drilling fluids prepared using Saudi palygorskite is investigated. Geothermal drilling fluids have been formulated by adding palygorskite to a combination of polymers and co-polymers in sea water to reduce fluid loss and maintaining good rheology while subjected to heat. Several mixtures exhibited satisfactory physio-chemical properties, however, the best results were obtained using polyanionic cellulose polymer and bacterially produced biopolymer. Umm er Rahduma clays have proven to be suitable for drilling operations because of their thermal stability and ability to yield in high electrolytic environment.