Present paper is aimed at disseminating learnings of designing and implementation of ASP flooding, a novel EOR technique, in a mature onshore field of ONGC. Scope encompasses ideation to successful field implementation including laboratory studies, pilot design & its execution and finally scaling up to full-field commercial implementation. Paper also covers monitoring strategies & methodologies used in the project which gave necessary insights for mid-course corrections resulting in around 200% improvement in production.

Pilot implemented in inverted 5-spot pattern with 4 injectors and 9 oil producers. Based on lessons learnt, field scale ASP with injection rate of 1120 m3/d through 14 patterns with 35 oil producers was implemented from July-19 with Alkali-2.5%, Surfactant-2500 ppm and Polymer-1500 ppm. Gradually, liquid withdrawal improved to ~1300m3/d from ~400 m3/d by optimizing oil wells. It resulted in oil improvement from 50 to 138 tpd. Initially, scheme could not perform. Maintaining ASP formulation and regular monitoring are crucial for success. Regular collection and analysis of ASP slug samples is done. Analysis revealed, reduction of Alkali may improve production.

It was observed, ASP slug viscosity of ~4cP is achieved with the used formulation against expected viscosity of 9.3 cP. It can happen with variation in water quality and slug parameters at field level. After detail analysis and revisiting laboratory studies it was confirmed that the lower than envisaged slug viscosity is the main reason behind sub optimal performance of the scheme. Because of low ASP slug viscosity the required mobility ratio could not be achieved which leads to poor sweep efficiency. It was also confirmed that reduction of Alkali shall improve slug viscosity.

Accordingly, ASP injection was carried out with ~1.2% Alkali along with Surfactant & Polymer of recommended concentration since Dec-21. The impact of improving sweep efficiency and regular intervention for optimizing oil wells improved oil production from 126 in Feb-22 to 250 tpd in Jun-22 with drop of water cut from 91% to 83%. Presently, it is producing 220 tpd with ~85% water cut.

Success of project is the outcome of rigorous efforts by deliberating mid-course correction to optimize quality and quantity of ASP solution, pattern balancing by tweaking withdrawal rates of producers so as to have a uniform flood movement and improve sweep efficiency.

ASP process provides synergistic benefit of three different types of chemicals to mobilize trapped oil in chemical EOR. The best way is to look back in lab to re-investigate how much tuning can be done to overcome field challenges. The side effect of alkali is studied and lowering its concentration is considered to be a better solution. Project success and its learning shall go a long way in implementation of future Chemical EOR projects.

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