Self-neutralizing well acidizing

Claim 2

A SELF-NEUTRALIZING AND BUFFERING ACID FOR BEING FLOWED INTO CONTACT WITH MATERIAL IN A RELATIVELY REMOTE LOCATION AND SUBSEQUENTLY BECOMING A SUBSTANTIALLY NEUTRAL SOLUTION, CONSISTING ESSENTIALLY OF: AN AQUEOUS SOLUTION CONTAINING FROM ABOUT 7.5 TO 15 PERCENT HYDROCHLORIC ACID, FROM ABOUT 0 TO 2 PERCENT HYDROFLUORIC ACID, AND MIXTURE OF UREA AND AT LEAST ONE AMIDE OF THE GROUP CONSISTING OF FORMAMIDE, DIMETHYLFORMAMIDE AND ACETAMIDE; AND A CORRELATION BETWEEN THE COMPOSITION AND CONCENTRATION OF THE COMPONENTS OF THE AQUEOUS SOLUTION RELATIVE TO THE TEMPERATURE AND TRAVEL TIME OF A SOLUTION RELATIVE TO THE RELATIVELY REMOTE LOCATION SUCH THAT THE SELF-NEUTRALIZATION IS DELAYED UNTIL THE ACID HAS REACHED SAID LOCATION AND SUCH THAT THE PH OF THE AQUEOUS SOLUTION IS SUBSEQUENTLY INCREASED TO FROM ABOUT 4 TO 6, EVEN THOUGH NONE OF THE ACID IS NEUTRALIZED BY THE MATERIAL CONTACTED IN SAID LOCATION.

Claim 3

A process for making a self-neutralizing acid that can be flowed into contact with a material in a relatively remote location and subsequently becomes a substantially neutral solution, which process comprises: compounding an aqueous acid solution consisting essentially of water, from about 7.5 to 15 percent hydrochloric acid, from about 0 to 2 percent hydrofluoric acid, and a mixture of urea and at least one amide of the group consisting of formamide, dimethylformamide and acetamide; and correlating the composition and concentration of the components of the aqueous solution relative to the temperature and travel time of a solution flowed into the relatively remote location so that the self-neutralization is delayed until the fluid reaches said location and the pH of the solution is increased to from about 4 to 6, even though none of the acid is neutralized by the material contacted in said location.

Claim 4

A process for making a self-neutralizing acid that can be flowed into contact with a material in a relatively remote location and subsequently becomes a substantially neutral solution, which process comprises: compounding an aqueous acid solution consisting essentially of water, from about 7.5 to 15 percent hydrochloric acid, from about 0 to 2 percent hydrofluoric acid, and a mixture of urea and at least one amide of the group consisting of formamide, dimethylformamide and acetamide; and correlating the composition and concentration of the components of the aqueous solution relative to the temperature and travel time of a solution flowed into the relatively remote location so that the self-neutralization is delayed until the fluid reaches said location and the pH of the solution is increased to from about 4 to 6, even though none of the acid is neutralized by the material contacted in said location.