The formation of sulfate scales arising from the injection of seawater into hydrocarbon-bearing formations for pressure maintenance and secondary oil recovery has been a significant problem in many onshore/offshore operations. To address this, batch scale inhibitor squeeze treatments, scale removal, and modification of the injection brine (sulfate removal, produced water injection, aquifer water injection) have been applied with varying degrees of success. The development of deepwater projects, where conventional scale control technology may be uneconomic for the control of mineral scale, has required a re-evaluation of the methods of scale inhibitor deployment.

For the past five years, BP Exploration has been developing a novel approach to the application of scale inhibitors with the objective of eliminating the requirement for both active scale inhibitor squeezing and scale removal operations. This has been achieved by the development of nano-sized, controlled release, solid scale inhibitor particles that can be added to the injection water such that the particles pass through the formation and release the scale inhibitor into the fluids near the production wells.

The principle of solid particle transport in porous media is demonstrated using core flooding tests and reservoir modelling. This confirms that solid particle transport is possible and that minimum retardation relative to the injected brine can be achieved. Static and dynamic release characteristics of the scale inhibitor formulations evaluated to date will be presented. The factors to be considered in the commercial manufacture and initial field trial results will also be presented together with the economic justification for this type of scale control process.

This technology offers a revolutionary scale control process that could eliminate the need for sulfate-reduction plants whilst still providing effective scale control within the reservoir and near-wellbore region for deep water developments.

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