ABSTRACT:

Packer fluids are used to provide hydrostatic pressure in the annulus for well control purposes or to prevent casing collapse. As such they must be capable of doing so for lengthy periods, be non-corrosive and capable of inhibiting corrosion. Completion fluids are used to permit the completion operations of a well. These may involve running completion strings, setting screens, gravel packs, downhole valves etc. To function effectively, completion fluids need to be able to provide hydrostatic pressure for well control and must be non-damaging to the reservoir to prevent loss of productivity. Historically, clear brines have been used for both functions. This is to obviate the chances of solids settling with the potential of:

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    Loss of hydrostatic pressure

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    Plugging of equipment

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    Plugging of and damage to formation permeability

However, the assumption that clean brines fulfil these objectives and fluids containing solids do not is misconstrued. At higher brine densities, corrosiveness, formation incompatibility, associated HSE issues and costs may mitigate against their use. For instance, some bromide brines are naturally corrosive and require treatment with corrosion inhibitors to be rendered non-corrosive. Such inhibitors may be damaging to the formation by altering wettability or relative permeability. There are also HSE issues attached to the use of these brines. This paper describes the formulation and application of fluids using microfine particles to produce fit-for-purpose packer and completion fluids, which minimise sag, corrosion & formation impairment, whilst maintaining hydrostatic pressure and well control. Actual field work done using the microfine weighting agents, manganese tetraoxide and a proprietary treated micronised barite with PSD's of ~1 micron D50 have been shown to provide packer & completion fluids, which meet the requirements described above

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