ASP Formulation Development Journey, Optimisation, Validation and Quality Control for Mangala Field

Mangala 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 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 (lower IFT), very low residual oil saturation, good thermal and aqueous stability, low adsorption, low chemical concentration and number of components among many other parameters. Initial formulation basis IFT was selected and tested under coreflood (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 and the formulation consisted of 0.3% surfactant and 3% alkali and 0.25% polymer in soft water which was used during very successful pilot (SPE 179700). The formulation has been further optimized to reduce the overall chemical quantity during full field (SPE 200445) with 0.25% surfactant and 2.5% alkali. Additionally, formulation has been further 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 involving more than 30 long linear corefloods under reservoir dead and live oil condition, 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.