Static, settled solids in production separators, free water knock out vessels, and gravity devices are harder to remove as time increases. This is due to mechanical consolidation and chemical binding.

Mechanical Effect – Consolidation

• Rearrangement of particles to more compact state by removal of liquid between grains
• This does not occur from clays/silt/fines located between sand grains as these small particles do not settle in water phase, but pass to oil and water streams
• Consolidation occurs from gravity, lubrication, and vibrations (platform/equipment) – and increases with time

Chemical Effect – Binding

• Occurs by bridging between grains or cementation
• Caused by wax, asphaltene, precipitates, bitumen, tar balls, corrosion products, bacteria, scale formation, iron sulfide, or viscous chemicals
• Onset from decrease in pressure and temperature in production separator compared to tubular and wellhead, plus chemical additions

Consolidated or cemented sand requires chemical, thermal, and/or mechanical action to unbind.

Keep sand fluidized – move or remove frequently!

The example in the header graphic shows a mixture of reservoir chalk and proppant sand settled into a production separator offshore Denmark. These solids have a gravel appearance which is due to the fine chalk particles cemented by scale to form gravel size “particles”. A close-up of the created particles is shown below. These chunks bridged over the sand pan slots and could only be removed by manual intervention after shutting down the separator.