American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Petroleum sulfonates are currently being evaluated extensively in surfactant enhanced oil recovery processes in laboratory studies, pilot field trials, and in semicommercial field tests. Consideration of surfactant manufacturing, product availability projections, product properties and laboratory oil recovery tests among available types of petroleum sulfonates establish that those produced directly and economically from abundantly available petroleum refinery feedstocks can be petroleum refinery feedstocks can be produced in volume to meet oil industry produced in volume to meet oil industry requirements. The diversity of crude oils ana reservoir constraints make it desirable to tailor surfactant systems to optimize oil recovery. Introduction Most of the many hundreds of currently existing U.S. patents directed to surfactant enhanced oil recovery processes disclose the use of petroleum sulfonates singularly or in various surfactant combinations. In spite of this plethora of petroleum sulfonate use claims, the technical literature is almost devoid of comparative information relative to the various types of available petroleum sulfonate products — those derived as low yield sulfonation "by-products" and those by direct higher yield petroleum sulfonation in which the sulfonate is the primary product — and to processes for their manufacture. Accordingly, this paper, addresses itself to filling this need, with greatest emphasis being placed on the comparison between placed on the comparison between conventional petroleum mahogany sulfonates and the newer petroleum sulfonates produced by direct petroleum sulfonation recently developed by the present authors and their associates. It is apparent that for the most part the oil industry's main technical thrust has been primarily directed towards developing the complex oil recovery process technology, whereas surfactant product and process development has been a secondary process development has been a secondary consideration, with some notable exceptions to be sure. While it has recently been reported (1) that crude oil sulfonate is now being produced by SO sulfonation, the resultant low yield sulfonate is directly converted to a dilute surfactant "slug" system and is thus beyond the scope of this study.