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