Abstract: The mechanism that salt affect colloid characteristic of the mud has been discussed. The components of amphoteric polymer salt tolerance mud have been introduced, and the field operation technology drilling through thick salt bed by using amphoteric polymer mud system has been summarized. The key of the salt tolerance drilling fluids is to maintain dispersity of the
bentonite particles by increasing the content of salt tolerance additives in mud. Results of applying the amphoteric polymer salt tolerance mud in Zalaloer oilfield show that the drilling fluid system has a pretty good ability to withstand salt, and the drilling fluid technology is reasonable in drilling thick salt bed.

Key words: amphoteric polymer, salt bed, plastic shale, clay, colloid characteristic