low shear rate viscosity increase method for drilling fluids and well maintenance containing calcined magnesia bridging solids, fluids and methods of use

摘要

"low shear rate viscosity increase method for drilling fluids and well maintenance containing calcined magnesia bridging solids, fluids and methods of use". The present invention relates to well drilling and maintenance fluids, and methods of drilling, completing or working over a well with them. Preferred fluids comprise an aqueous liquid, a water soluble polymer viscosifier (preferably gum). xanthan), a polymeric fluid loss control additive (preferably a partially cross-linked partially depolymerized hydroxyalkyl ether derivative or a partially cross-linked and partially depolymerized starch hydroxyalkyl ether derivative), a bridging agent comprising a particulate calcined magnesia having an activity index of greater than about 800 seconds, and an additive selected from the group consisting of citric acid, alkali metal salts of citric acid, ammonium citrate, and mixtures thereof in an amount sufficient to increase the low shear rate viscosity of the fluids, preferably from about 0.05-5 ppb, more preferably from about 0.15-3 ppb. The present invention further relates to a method of increasing the low shear rate viscosity of fluids containing a water soluble polymer and a calcined magnesia bridging agent having an activity index of greater than about 800 seconds