APPLICATION OF PGS SALT-SATURATED MUD IN DRILLING OPERATION

The Pregelatinized Starch (PGS) is of good property of reducing the loss of water. Muds made of clay, salt-saturated water and PGS can form a thin and dense mud cover upon the well wall during drilling. Further, the PGS salt-saturated mud can restrain the clay within the well wall from absorbing water and swelling. So that it can prevent the well wall from collapsing. The field tests show that this kind of muds especially suits to drilling the high salt and high calcium strata, such as salt, gypsum and glauberite formations. The important matters for the PGS muds are to keep the salt saturated, to restrict the useless solid content and to maintain the pH of 9 to 11. The PGS salt-saturated mud is of low cost, easy to prepare and to use in drilling operation.