Study On High Temperature Resistant Xanthan Gum Based Thickener For Oil Well Cement Slurry

Reliable cementing quality is an important guarantee for oil and gas production.With the exploration of deep well, the temperature in the well bottom is higher. Thiswill put high demand of cement slurry. Under high temperature, the cement particlesmove faster and adhesion force is destroyed. In addition, segment flexibility ofconventional polymeric additives becomes better. These factors accelerate thesettlement of cement particles under the gravity. Serious settlement will cause theoccurrence of gas channeling. This will affect the quality of cementing. Then we needto add some thermo-stabilizers. There may be two solutions to this problem, one isadding ultrafine materials, and the other is adding high temperature resistantthickener.In this paper, we try to use the way of adding high temperature resistant thickenerto solve this problem. Xanthan with helical structure was used as base material forthis thickener. In aqueous solution, using chemical free radical grafting method,resistant monomers2-acrylamide-2-methyl propane sulfonic acid, N-vinylpyrrolidone and dimethyl diallyl ammonium chloride were introduced into the naturalmacromolecule xanhan gum. After purification, heat-resistant salt-tolerant copolymerswere prepared. The infrared and SEM-EDS results indicated that thermal monomerswere successfully grafted onto xanthan gum.After reviewing graft reactions, we found the best initiation system and thesuitable monomer and xanthan quality ratio. Among the initiators used in this article,oxidation reduction-cerium ammonium nitrate initiation system can get themaximum grafting rate. Considering both grafting ratio and grafting efficiency, thesuitable quality ratio between monomer and xanthan is between2and3. Modifiedxanthan gum possesses better solubility and alkali resistance. The viscosity of XG andXG-grafted both increase with the salinity，while， salinity effect is stronger to XG.Under90℃, the settlement stability of slurry with XG-grafted thickener is good. Afterstanding, the amount of free liquid on the surface of slurry can be neglected. Under140℃, during shutdown experiment, the viscosity of slurry with XG-grafted is stable.After curing, the slurry has good uniformity and has no wrapped heart problem.Under high temperature and pressure curing, slurry with XG-grafted thickener has a better liner and right angle shaped consistency curve. The slurry with XG-grafted hashigher viscosity than slurry with XG.