Solids Handling for Upstream Oil & Gas Industry: Step 4 - Dewatering (B-FSM038)
The fourth step of solids handling in the upstream oil & gas industry is Dewatering. This step is used to remove free liquids (mainly water) from sand slurry to minimize disposal volume (covered in detail in FSM-M9).
- Reduce the disposal volume by 90% and produce sand “cake”
- Will remove hydrocarbon liquids (aids cleaning) and other liquid contaminants
There are two types of dewatering systems – open (non-hazardous) or closed (hazardous)
- Open – liquids returned to open drain, sand/vapors open to atmosphere
- Closed – liquids captured to closed drain, vapors captured to vent system, and solids not exposed to atmosphere or personnel
Water removal using gravity drain is relatively fast (10-15 minutes)
- Dewatering rate reduced by increased liquid viscosity, clay/silt content, total particle specific surface area, and particle packing density
Unit Processes for Dewatering
- Use gravity or enhanced forces
- Gravity drain most common – simple/inexpensive
- Pressure filtration – more complex but faster
- Cyclonic – 1st stage in two-step process (followed by gravity), removes bulk liquid from dilute slurry
- Open hanging filter-bag or closed bin-bag
- Both use rapid-weep, oleophobic dewatering bag
- Dewatering bag or bin serve as transport device (combined step)
Dewatering is detailed in module M9 and will be covered further in a future post.
Three unit-process examples below show dewatering system employed in the upstream oil & gas industry. The first (left) shows a two-stage open dewatering system using desilter cyclones for bulk liquid removal and open-frame dewatering bag for final removal. The middle system shows an open system with a cabinet-trolley enclosure used to treat slurry from a produced water desander. The system on the right shows a fully enclosed dewatering bin with transport cage for hazardous environment containment.
- Rawlins, C.H., “Sand Management Methodologies for Sustained Facilities Operations,” paper 164645-MS, North Africa Technical Conference & Exhibition, Cairo, Egypt, Apr. 15-17, 2013.
- Rawlins, C.H., and Wang, I. I., “Design and Installation of a Sand Separation and Handling System for a Gulf of Mexico Oil Production Facility,” SPE Production and Facilities, paper 72999, Vol. 16, No. 3, 2001, pp. 134-140.
The next article will detail Step 4 on Dewatering.