The design and application of a chemical EOR pilot for a complex, low-permeability waterflood will be presented. Our focus has been on developing appropriate field application options, allowing flexibility of operation against a background of reservoir complexity and uncertainty.

Australia’s Barrow Island Windalia reservoir, the nation’s largest onshore waterflood, was developed in the late 1960s. Cumulative oil production to date is over 288 MMSTBO.

Planning a chemical EOR scheme needs to address the following reservoir and production characteristics:

• highly heterogeneous, very fine grained, bioturbated argillaceous sandstone, high in glauconite;
• high porosity (0.28) but low permeability (5 mD with 20 mD+ streaks);
• production and injection necessarily stimulated by induced fractures
• highly saline and hard brine; and,
• large waterflood pattern volumes (10 MMbbl at 20 acre well spacing).

Initial screening recommended that polymers be considered for sweep improvement and conformance control, although reservoir complexity presented a challenge.

In this paper, we summarise the subsurface studies, and subsequent petroleum engineering and facilities design, which lead to the successful pilot start-up in May 2009. In particular, we discuss the implications on design and operation of a pilot in a Class A nature reserve. Results from the proposed polymer pilot flood will allow assessment of further chemical EOR applications and potential field-wide scale-up.