Abstract
Polymer flood process has the potential to significantly improve sweep efficiency in the fields with viscous oil, due to unfavorable water-flood oil-water mobility ratio resulting in a relatively inefficient water-flood. A successful field implementation would lead to extended production plateau and increased ultimate recovery (EUR). Cairn India Ltd is engaged in Oil and Gas exploration and production in RJ-ON onshore block in India. Mangala oil field is the largest discovered field with significant oil production potential (Total estimated water flood recovery of around 37 %). The field which contains moderately viscous but waxy oil with high pour point is currently under hot water flood to provide pressure support, sweep and prevent any in-situ wax drop-out. Post success of a polymer pilot trial, the full field polymer flood project is being implemented in the field with the concept of a Central polymer preparation plant distributing the concentrated polymer mother solution to the injection wells which are scattered across the field. The mother solution is diluted with the injection water to required polymer concentration before final injection into the well. Full field Polymer Injection it is expected to yield additional recovery of 5–7% of the STOIIP over base water flood.
This paper discusses the challenges faced during the execution of the polymer injection in the full scale with respect to,
Supply chain management of polymer w.r.t framing the polymer supply contracts, screening of multiple vendors in different geographical location and the logistics management of large volumes of polymer,
Laboratory techniques in screening the polymer, challenges faced in laboratory measurements including viscosity measurement in aerobic/anaerobic conditions, low shear high pressure sampling, and compatibility of oil field chemical additives with Polymer,
Operational challenges including viscosity with available water quality & higher oil in water, TSS, Fe content and impact of temperature variation on viscosity of mother solution and diluted polymer solution,
Produced fluid handling challenges with Polymer breakthrough with respect to adequacy of oil-water-gas treatment facility to handle emulsion, scaling/gelling issues in heat exchangers and the capacity limitations caused by viscosity and hydraulics.
To summarize, for the full field polymer injection, the challenges discussed with respect to unwieldy logistics of polymer procurement, mother and dilute polymer solution preparation at low shear and high pressure environment followed by polymer breakthrough resulting in tighter emulsion, etc need to be addressed proactively in order to achieve the targeted recovery from the Project. The focused efforts on these areas of concern are the drives for the success of all the stakeholders.
