THE FUNCTION EFFECT OF HYDROCHLORIC ACID DURING ACIDIZATION OF SANDSTONE FORMATION USING MUD ACID

Acidization of sandstone formation is generally performed using acid(mixture of HCl with HF).Many reasearch results show that the effectiveness of acidization not only depend on the HF in mud acid,but also on the HCl.So far the function mechanisms of hydrofluoric acid(HF) have been elaborated,but that of hydrochloric acid(HCl) hardly yet.For this reason,the four aspects influencing on the results of HCl in mud acid during sandstone stimulation are discussed in this paper:(1) the distribution of the attacking species of aqueous hydrofluoric acid;(2) the stoichiometric coefficient of the reaction of acid with rock;(3) the etchling ability of hydrofluoric acid;(4) the re-precipitation of reaction products.