Paper: An Acid-Solvent System For Removal of Downhole Skin Damage

As early as 1895, Herman Frasch recognized a need for acid additives in acid stimulation treatments. His observations and subsequent patent spelled out the need for an acid corrosion inhibitor. During the span of years from the early 1930s to the mid 196Os, much advancement was made in the field of developing additives for hydrochloric acid stimulation. Surfactants, corrosion inhibitors, buffering agents, and reaction time retarders as we know them today, had their beginnings. The one notable factor about these advances is the fact that all were truely additives for the acid. That is, the materials were added to the acid in small quantities to alter the properties of the treating fluid. Seldom were the additives used at concentrations exceeding 1%. In the mid 196Os, alcoholic acid treating solutions were introduced. This launched an era of more basic changes in the whole nature of the acidizing fluids. This was no longer an additive because a significant portion of the treating fluid might now be termed as a solvent. Later in the decade came the use of chemically stabilized dispersions of aromatic solvents in an acid external emulsion. Then in 1971, the use of mutual solvents was introduced. Each of these advancements offered new possibilities and improved the treatment results by helping the acid past physical barriers so it could perform the job it was intended to do. During the same decade, much work was directed to enhanced oil recovery through micellar flooding. From this technology came the concept of the micellar acidizing solvent. The following sections will compare the properties and use of the popular and widely used solvent systems to the newest - a micellar acidizing solvent.