An all-inclusive laboratory workflow for the development of surfactant/polymer formulations for EOR in harsh carbonates

Abstract

Carbonate reservoirs are challenging for chemical EOR, particularly in selecting fine-tuned chemical formulations which combine high performance, stable behavior, and trouble-free operations. The design of suitable formulations requires substantial laboratory work and a solid methodology. In this paper, a systematic all-inclusive laboratory workflow to design a surfactant-polymer (SP) formulation for a carbonate reservoir is presented. The experimental steps were clearly delineated including the preparation of representative oils. A key novelty of the adopted workflow is the integration of topside assessment. Beside a clear layout of the methodology, the work demonstrates that a surfactant-polymer formulation can successfully be designed for high temperature carbonate reservoirs and provide encouraging guidelines with respect to SP impact on topside facilities.In summary, the results demonstrate the potential of a binary surfactant mixture of a highly hydrophobic Olefin Sulfonate (OS) and a slightly hydrophobic Alkyl Glyceryl Ether Sulfonate (AGES). The results also illustrate couple of extended stability polymers suitable for high temperature carbonates: an associative polymer, and an AM/AMPS (acrylamide/2-acrylamido-2-methyl propane sulfonic acid) copolymer. Moreover, single-phase displacements clearly supported the SP formulation transportability across and within the porous media. More importantly, the developed SP formulation was capable of recovering around 62% of the remaining oil in core post waterflooding (ROIC). Finally, in terms of topside effects, the presence of surfactant and polymer in the brine clearly improved the separation kinetics; nevertheless, a manageable deterioration in separated water quality was observed.