Case Study: ResInject ICD Offers Potential for 1%–10% Increase in Oil Recovery

New technology increases sweep efficiency in Statoil Norwegian Sea development

Challenge: Improve pressure support and sweep efficiency on the sandface in two separate structures in the Urd field of the Norwegian Sea.

Solution: Installed ResInject injection control devices tailor-made for injection wells.

Result: Optimized pressure support and sweep efficiency for all reservoir zones.

Separate structures consist of heterogeneous pay zone

Located in the Norne area of the Norwegian Sea, the Urd field was developed in 2004–2005 as a satellite to the Norne floating production, storage, and offloading (FPSO) vessel and was operated by Statoil. Urd comprises two separate structures, Svale and Staer, which are located 4 and 9 km [2.5 and 5.6 mi], respectively, from Norne. Both the Svale and the Staer satellites consist of heterogeneous pay zones. Recoverable reserves for Urd are estimated at around 70 million bbl of oil along with some natural gas. The Urd field was originally planned to eventually include a total of five oil producers and three water injectors. Gas from the Norne FPSO was injected directly into the wells, reducing wellstream density and increasing production. Statoil wanted to improve pressure support and sweep efficiency on the sandface.

ICD injector ensures improved water distribution

Statoil evaluated the use of the ResInject inflow control device (ICD) because of its self-regulating effect, which prevents a thief zone from taking excessive injection fluid volumes. The overall result is improved water distribution and better pressure support and oil drainage in all zones.

There were three main reservoir management goals. First, the injector ICD implementation had to optimize pressure support and sweep efficiency for all reservoir zones, independent of heterogeneities. Second, if connected to the producers, the ICDs had to defer water breakthrough in high-permeability zones. Third, the ICDs had to avoid one or more fractures dominating the water distribution.

Simulations suggested two extremes of resulting productivity. If a highly permeable channel existed between the injector and the producer wells, there would be a 10% increase in cumulative oil production. If no channel existed, the injector would confer only a 1% increase.

Statoil and Schlumberger qualified and installed the devices, which had nozzle sizes designed for this particular case. The Reslink screens and ICDs that were tailor made for injection wells were gravel packed to restrict annular flow and isolate the zones, optimizing regulation of reservoir heterogeneities.

ICD benefits improve reservoir model

The project objectives were achieved. The test program verified a robust system design using raw seawater without compromising the longevity of the injector. The injector completion was successfully installed with the gravel pack, providing the necessary zonal isolation. Simulations identified the possibility of controlling injection rates into the individual zones.

Compared with a standard screen completion, the ResInject injector completion was much less influenced by permeability contrasts and fractures, meaning sweep could be improved. The available data during the first year after startup showed that the total injection was in line with the design. The data also indicated that the injector had improved sweep; however, this result was not conclusive without the injection profile’s verification by a production log. Thus, a PLT log of the ResInject installation confirmed that even at different surface injection rates, the injection profile maintained its balanced nature in the presence of heterogeneity from heel to toe.

Dynamic reservoir simulations showed a potential for a 1% to 10% increase in oil recovery with the ResInject injector solution.

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