Research and Application of Amphoteric Polymers for Drilling Fluid

Abstract As the inhibition ability is not strong enough and the tolefance ability of solid contamination is low for usual polymer drilling fluid, the amphoteric polymer drilling fluid is suggested to solve above problems after analyzing and researching interactive mechanism and components of polymer drilling fluid as well as structure character of polymer molecule. The inherent character of amphoteric polymer molecule makes it not only to have strong inhibition but also to improve rheological property of drilling fluid. The application in 15 oilfields (nearly 4000 wells) in China demonstrates that the amphoteric polymer drilling fluid has strong inhibition, can retard "mud-making" of shale formation, keeps low-solid content and wellbore stable. The amphoteric polymer drilling fluid has excellent rheological property to make full use of jet-bit drilling and achieve significant effectiveness of increasing drilling rate. The obvious results in protection of oil formation have been achieved.