Characterization and Oil Recovery Observations on a Series of Synthetic Petroleum Sulfonates

Synthetic sulfonates for application in enhanced oilrecovery are of increasing interest. Because of the needto explore the range of candidates potentially available atvarious costs from the petrochemical industry, a series ofnine samples was prepared for distribution with financial suppose of the U.S. DOE. This paper briefly describesthe samples and, in more detail, the characterization ofthe samples for oil recovery. The characterization included determination of optimal salinity, stability ofaqueous dispersions in brines containing sodium chlorideand calcium ion, and oil recovery and loss of sulfonate in1-ft (0.305-m) Berea cores. Introduction Most current work in surfactant systems for enhanced oilrecovery is based on sulfonates, either petroleum(natural) or synthetic. The synthetic sulfonates discussedin this paper are those made by alkylation of an aromatic hydrocarbon with a selected olefin, followed by sulfonationof this alkylate. Interest in these synthetic sulfonatesis evident from numerous patents and publications fromseveral laboratories. The major published work in this area, by Reed andHealy, stems from earlier studies that generated seriousquestions as to the effect of fractionation of petroleumsulfonates when used in reservoirs. Interest in andwork with synthetic sulfonates has increased steadily inthe Sun Co. laboratories over the past years because offavorable experimental results. However, availablesamples of synthetic sulfonates have been limited; theydid not include agents that probably would be thelowest cost materials available from current petrochemicaloperations. With the question of cost effectiveness inmind and with the expressed interest of a number of oilrecovery laboratories, Sun approached the Energy R and DAdmin. with the following proposal:Sun wouldprepare large samples of a representative set of syntheticsulfonates,the New Mexico Petroleum RecoveryResearch Center would distribute the samples tointerested laboratories and would receive and distributeinformation from these groups, andthis informationwould include characterization studies on the sampleswith preliminary studies by the New Mexico and Sun laboratories. This work has now been completed. The Sun Applied R and D group in Marcus Hook, PA, did the preparative work. The samples are describedbriefly in a following section; complete description isavailable in Ref. 5. This paper describes characterization of the synthetic sulfonates by optimal salinityexperiments, studies of aqueous dispersions in selectedsodium chloride and calcium chloride concentrations, and oil-recovery experiments in 1-ft (0.305-m) Bereacores. Plans for this work required a decision on the levelof concentration of sulfonate to use. One philosophyexemplified in published work is that the level should below so that, for an acceptable total amount of sulfonate, the %PV of the slug could be as large as possible. Thisapproach is an advantage in efforts to improve theoverall conformance of the recovery system in areservoir. Some interesting results have been obtained with synthetic sulfonates at the level of 2% active concentration.In studies of the stability of aqueous dispersions asin the salinity grids, 1.5% sulfonate was used. Thisvalue is expressed in terms of the aqueous phase; nosignificant oil phase was present. SPEJ P. 226^