TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe first publication on the use of slag as a material capable of substituting the traditional Portland cement in well cementing appeared in 1991, when it was seen that it could be added to drilling fluid and solidify it with some advantages over traditional methods.As a result, only recently, the use of this emerging technology has been suggested for situations where difficulty in removing the drilling fluid mud cake has been expected, as in HP/HT wells, for example. In this case, the practical rules for a successful cementing operation cannot always be implemented.As these high temperature wells are fundamental to the exploitation of important Brazilian fields, it was decided, as one of the strategies for overcoming the difficulties in obtaining good cementing results, to invest in evaluating the performance of the slag-mix technology.An extensive research project has therefore been conducted in a large-scale wellbore physical simulator, with the principal objectives of investigating the ease or difficulty of mixing the slag-mix and to evaluate the bond quality obtained after cementing and acidizing the well. Thus, the object of the present paper is to investigate the performance of slag-mix slurries under three distinct scenarios: cementing surface casing; cementing production casing at medium temperatures; and cementing production strings at high temperatures. The resistance of the set slurry to the attack of HCl / HF is measured in a physical simulator under static and dynamic conditions.