This paper presents the design of a polymer flood pilot in a very heterogeneous, sour Heavy Oil reservoir (referred to as HO Reservoir in this paper), which has three times the salinty of sea water with a high mineral content. In addition, the paper illustrates the methodology for the pilot design, location selection, modelling, water source selection, data acquisition plan, and polymer selection and testing.
The purpose of the polymer flood pilot is to derisk a full field development plan, which aims at improving recovery by flooding processes in a shallow Heavy Oil Field with only two years of production data. The aim is to demonstrate polymer flood technical feasibility in the field and to provide data to evaluate economic viability for further expansion to full field. Therefore, the pilot had to be designed in such a way that it leads to representative results and data for the full field development and enables identification of potential risks and reduction of uncertainties. The multi-well pilot is preceded by polymer lab tests and by single-well injection testing.
By a thorough field analysis including static and dynamic modelling, a pilot pattern shape and size were selected and the pilot wells were drilled last year. An extensive data acquisition plan has been made to optimize learnings from the pilot execution phase. Pressure gradients and vertical interference tests measured in open hole on the injector wells show the presence of short scale heterogeneity. This provided also learnings for the variable water cut development observed in other parts of the field. Since produced water was selected as water source for chemical EOR, another challenge that was successfully overcome was the qualification of a HPAM polymer tthat performed stably under highly saline water conditions and high dissolved H2S concentration. This was the result of a comprehensive polymer formulation laboratory program and subsequently followed by a single well chemical tracer test.
Polymer flood in a highly saline, sour reservoir is unprecedented worldwide and needs careful derisking by a pilot. Using produced water instead of seawater will reduce disposal and treatment costs as well as follow KOC's environmental strategy.