Aspects of Acid Additive Selection in Sandstone Acidizing
Authors: Sutton Gary D. , Lasater R.M. 
Published: December 2007

This paper was prepared for the 47th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in San, Antonio, Tex., Oct. 8–11, 1972 Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
This investigation includes a study of stabilization of South Louisiana crude oil-acid emulsions by fine solids, and the influence of corrosion inhibitors and surfactants. The wettability of silica surfaces also was investigated. Wettability of the solids was found to have little effect on crude oil emulsion stability in the presence of non-emulsifying surfactants, but would be important when subsequently contacted by formation fluids. The apparent sand wettability is a function of the combined corrosion inhibitor-surfactant properties. Reduced adsorption of corrosion properties. Reduced adsorption of corrosion inhibitor was observed when acid solutions contained a mutual solvent.

Introduction
Treatment of sandstone formations with acid solutions, particularly mixtures of hydrochloric-hydrofluoric acids, has received considerable attention in recent years. Most concern has been in describing the acid-rock reaction presenting theoretical predictions of pore development and acid penetration, and determining the effects of acid flow through cores.
Only Gidley has reported any recent work emphasizing the part that acid additives may play in successful sandstone acidizing. Even play in successful sandstone acidizing. Even though the use of acid additives is certainly not new, their complex interactions and adsorption properties on sand and clay are not fully understood.
Our investigations are concerned with two aspects of maintaining compatibility between the treating fluid and formation components:the role of formation fines on the emulsification tendencies of acid solutions with crude oil andthe influence of corrosion inhibitor-surfactant interactions on formation wettability both in acid solutions and in brine.

SPENT HF ACID/CRUDE OIL EMULSIFICATION

Crude Oils Selected for Testing
The crude oils used for the emulsion studies were gathered by random selection from the Gulf Coast area in Louisiana. These crudes include samples from both onshore and offshore wells producing from sandstone formations. An exception to this was Morrow formation oil from the Texas Panhandle. The crudes are listed in Table 1 by common name.
Comparison of the physical properties of these oils shows that this list contains a broad spectrum of crudes. Physically, these crudes ranged from viscous, black oils (White Castle, (GED and Morrow) to a thin, amber oil (Gibson).