First Polymer Injection in Deep Offshore Field Angola: Recent Advances in the Dalia/Camelia Field Case
The Polymer injection project on the Dalia field, one of the main fields of Block 17 in deep offshore Angola, is a world first in both surface and subsurface aspects. An 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. The 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 (first oil was in December 2006)
- With much wider well spacing than in any other project
- Under high-salinity conditions (>25 g/L)
- With the specific logistics of a remote deep offshore area
A phased approach has been retained in order to progressively derisk the project, starting from a single-well, short-duration injectivity test, followed by a full line injection in the three injectors of one of the reservoirs, and hopefully concluding with an injection extension.
A single-well, short-duration injectivity test was successfully implemented in the first quarter of 2009. The Phase 1 project started on 8 February 2010 in the Camelia reservoir. Viscosified water was injected into one of the four injection lines of the Dalia field (average BSW) of 20% on the associated producers at beginning of Phase 1 polymer injection]. By December 2011, more than 5 million bbl of cumulative of polymer solution has been injected in the Camelia reservoir.
The specificities of the Dalia field (large well spacing and low BSW at polymer-injection startup) 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 to accelerate the sanction for a full-field development. The studies concluded with a recommendation to drill a well to sample in situ the injected viscosified water. Location of the sampler well at a distance of 100 m from an injector, and the best timing to drill the well, were based on a 4D-seismic-data history match and waterflood-performance forecast.
Changing the Mix: A New Approach to Polymers for Offshore EOR
Researchers from Chevron are looking into a new approach to understand the drivers of polymer hydration. How might this affect the design of mixing systems in the field, and could it affect offshore EOR applications?
Case Study: Design of Injection Facilities for CO2 Recovery
A pilot project demonstrates that facilities design plays an important role in providing sources of CO2 for the gas-handling process for injection into a carbonate formation as a tertiary recovery mechanism.
The Effect of CO2 Injection on Corrosion and Integrity of Facilities
The paper discusses the main factors affecting CO2 corrosion, provides an assessment of what to look for in major equipment, and details recommended material of construction and corrosion mitigation/control methods.
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