First Polymer Injection In Deep Offshore Field Angola: Recent Advances on Dalia/Camelia Field Case

Abstract

Abstract The Polymer Injection Project on the Dalia field, one of the main fields of Block 17 in deep offshore Angola, is a world first for both surface and subsurface aspects. In depth integrated geosciences and architecture study culminated, in January 2009, in the start of polymer injection in one of the Dalia water injection wells. Dalia field is a high permeability sandstone reservoir (> 1 D on average) and contains a medium viscosity oil (1 to 11 cP under reservoir conditions). The key challenges of the project were to start polymer injection: – Very early in the field development since first oil was in Dec. 2006 – With much wider well spacing than in any other project, – Under high salinity conditions (>25g/l) – With the specific logistics of a remote deep offshore area. After a very positive single well injectivity test early in 2009, additional single well injectivity tests were performed end 2009 on three Dalia wells in various configurations. They demonstrated an injectivity of the polymer solution that satisfies the Field Development requirements in term of voidage replacement, as defined in the water injection base case. During this testing period, the capacity of the logistics and surface facilities (capacity of 7 t/day) to successfully prepare the polymer solution on board the FPSO have been demonstrated after specific difficulties and issues were identified and fixed. Based on these positive results, a Phase 1 project was sanctioned and started on 8th February 2010 on the Camelia complex. Viscosified water is injected in one of the four injection lines of Dalia field (average BSW of 20% on the associated producers at beginning of Phase 1 polymer injection). By mid June 2010, more than 3 MM bbls of cumulative of polymer solution have been injected in the Camelia reservoir. The specificities of the Dalia field (large well spacing and low BSW at polymer injection start up) mean a late response if the usual EOR monitoring techniques are applied. Various monitoring options were considered to verify the injected polymer solution properties in-situ, and accelerate the sanction for a fullfield development. The studies concluded on a recommendation to drill a well to sample in-situ the injected viscosified water. Locations of the sampler well at a distance of 100m from an injector, and best timing to drill the well were based on 4D seismic data history match and waterflood performance forecast.