ASP Formulation Development Journey, Optimisation and Validation for Mangala Field

Abstract

AbstractMangala is a large low salinity, high quality fluvial oil field reservoir in India with STOIIP of over one billion barrels of waxy and moderately viscous crude. Aqueous based chemical EOR has been identified as the most suitable technique to improve recovery over waterflooding. The objective of this paper is to describe the ASP formulation development journey for Mangala which involved more than 30 corefloods till date with evolution of formulation design changing over time. The final selected formulation has been successfully tested in upper layer of Mangala field during pilot and is being planned to be used in full field.Initial formulation design was done using IFT (interfacial tension) and adsorption measurements approach. Later the formulation design was done using classic phase behavior approach which allowed quick and robust evaluation of large number of chemicals in a short duration. Typically, the formulation development involves phase behavior tests, aqueous stability test, salinity gradient design, dead oil and live oil coreflood on long linear synthetic and reservoir core plugs. A successful formulation shall have low viscous microemulsion phase, solubilization ratio greater than 10 (ultralow IFT), very low residual oil saturation, good thermal and aqueous stability, low adsorption, low chemical concentration and fewer components among many other parameters.Initial formulation basis IFT measurements was selected and tested under multiple corefloods (IPTC 12636). Later, basis the phase behavior approach, another formulation consisting of 0.3% surfactant and 0.3% co-solvent was formulated (SPE 129046). For Mangala, solubilizing paraffinic waxy crude required usage of large carbon chained Alkyl Benzene Sulfonate. Formulation with hydrophobic surfactant required addition of a hydrophilic surfactant and a co-solvent. Co-solvents, though improve electrolytic strength, add significant chemical cost and are some-times unstable. Finally, a highly hydrophilic alcohol alkoxy sulfate was selected to substitute the role of co-solvent but still maintain enough electrolytic strength. The formulation consisted of 0.3% surfactant, 3% alkali and 0.25% polymer in soft water which was used during a successful pilot (SPE 179700).The formulation has been further optimized to reduce the overall chemical quantity (SPE 200445) to 0.25% surfactant and 2.5% alkali. Additionally, formulation has been validated on other layers of Mangala field under high pressure live oil phase behavior and live oil reservoir coreflood.This paper discusses ASP formulation development approach, technical requirement, development journey of formulation for successful Mangala ASP pilot, optimization efforts undertaken to reduce the chemical usage and validation of formulation for other layers of Mangala reservoir. This paper also briefly discusses lab quality control guidelines that is being developed for large scale procurement of chemicals for full-field ASP floods.