Water injection, or waterflooding, is a common method for secondary recovery of hydrocarbons. It entails injecting water into the reservoir to maintain pressure, and sweeping oil to the producing wells. The implementation can significantly improve production and oil recovery, prolonging a field’s lifetime. Reservoirs produced by pressure depletion alone can benefit significantly from waterflooding implementation.
Water injection is a method applicable for both greenfield and brownfield developments alike and there are significant benefits for both applications.
Some analysts estimate that waterflooding can increase reservoir production volumes by as much as 50%. The success of water injection depends on how well each reservoir’s characteristics and needs are understood.
Waterflooding can be performed by using a variety of different water qualities—ranging from the injection of raw seawater, produced water and filtration.
These waterflooding techniques all utilize an inexpensive and sustainable resource for increased oil recovery: water. But what the methods fail to consider is the quality of the injected water and its compatibility with the reservoir fluid characteristics. Such failure could cause reservoir plugging, souring and scaling.
To be able to extend the life of the field, secondary recovery methods must be optimized and exploited to their fullest.
Subsea water treatment
Subsea water treatment enables reservoir engineers to inject as much water as they need—when and where they need it—without relying on topside infrastructure. This is made possible by National Oilwell Varco’s (NOV) subsea water treatment system Seabox.
In addition to applications in the offshore production sector the Seabox module can be combined with filtration and reverse osmosis membranes to create a system that’s capable of turning seawater into drinking water, prompting interest from several nations in Africa and the Middle East.
The Seabox system increases flexibility for water injection by moving water treatment to the seabed, thereby allowing injection to continue independently of platform shutdowns. This decreases the demand for added chemicals and power consumption while allowing for marginal asset developments with large step outs and enabling operation of unmanned platforms.
By adding a Seabox module into reservoir management strategy, operators will be free to consider water injection on marginal field developments they previously found economically impossible.
Dollars and cents
While these benefits have been well understood for some time, it’s taken many years—and significant investments in research and development—to make subsea water treatment a reliable, economically viable proposition for oil companies. But that’s no longer the case: The Seabox treatment module achieved a Technology Readiness Level 6 certification last spring.
At the end of 2017, National Oilwell Varco (NOV) made headlines when it secured a contract for Seabox subsea water treatment system. ConocoPhillips deployed the system at an offshore installation in the North Sea for an extended test they plan to complete early this summer.
Development, which first began more than 16 years ago, was made possible by a series of joint industry projects backed by the Norwegian Research Council, ConocoPhillips, Equinor and several other oil companies. These projects provided roughly NOK 150 million ($17.4 million) in funding and NOV contributed a similar amount.
You can view a video documenting the installation process below.
· Disinfection and particle settlement at the seabed
· Pretreatment functionality to existing topside processing facilities
· Enables long step-outs, making water injection a possibility for marginal field developments
· Increase sweep efficiency in the reservoir
· Reduced carbon footprint