The second step of solids handling in the upstream oil & gas industry is Collection. This step may also be called accumulation or concentration. The purpose is to gather all the separated solids into one (or few) central location and isolate from the process pressure and flow.

• Gather: minimize pressure letdown points and simplify handling locations
• Isolate: remove from process pressure & flow for further handling without interrupting production
• This is normally a batch process

It is very important to remove the sand from production while minimizing the amount of process fluids or contaminants with the solids. Multiphase and produced water desanders often use an externa/secondary accumulator with a clean water bath to minimize hydrocarbon ingress. Jetting systems are a poor design that lose large amounts of associated process fluids.

Valve selection is important for high pressure slurry purge and pressure letdown (see B-FSM-30).

Unit Processes for Collection

1. Simple static vessel or chamber that can be isolated, vented, and flushed (batch process)

• Wellhead desander accumulator
• Produced water desander accumulator
• Process tank that is not part of continuous production

2. It is helpful to fill the vessel/chamber with clean water (any source) in which to deposit the sand slurry

• Aids cleaning (oil removal)
• Important to introduce slurry into a water bath to prevent plugging

Separation Examples

Three unit-process examples below show collection equipment employed in the upstream oil & gas industry – these are 1500#, 600 liter wellhead desander accumulator, 900#, 108 liter wellstream desander accumulator, and accumulation section of a 150# produced water (liner) desander.