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Sand Cleaning – Cyclonic Cleaning System Overview (post B-FSM-141)

The cyclonic cleaning system consists of a skid package designed around three process loops;

  • Slurry Receiving & Dewatering
  • Sand Cleaning
  • Cleaned Slurry Disposal

Each of these loops will be detailed in subsequent posts – and are introduced below.

Slurry Receiving & Dewatering Loop (Green Loop)

This loop receives the oily sand. Sources can be from a multiphase or produced water desander (accumulator), jetting system, drains/blowdown, or any other oily sand source. The slurry is received and the bulk associated water is removed and return to drains or collection. Initial cleaning of free oil takes place in this loop. The dewatered sand reports to the accumulator vessel.

Sand Cleaning Loop (Red Loop)

The accumulated dewatered sand is recirculated in a closed-loop via jetting device, pump or eductor, cleaning cyclone, and back into the accumulator. Slurry is pumped around this loop until the sand is cleaned.

Cleaned Slurry Disposal Loop (Blue Loop)

The cleaned sand is removed from the accumulator via the jetting device and eductor/pump. This sand reports directly to overboard discharge – often via a caisson – or to a dewatering/bagging station for transport to shore.

References:

  1. Rawlins, C.H. and Wang, I. 2001. “Design and Installation of a Sand-Separation and -Handling System for a Gulf of Mexico Oil Production Facility”. SPE Production and Facilities, August, pp. 134-140. https://doi.org/10.2118/72999-PA
  2. Rawlins, C.H. 2019. “Enhanced Production Through Surface Facilities Sand Management.” SPE Distinguished Lecturer presentation. Link here

Next week I will continue discussion on cyclonic sand cleaning system component selection.

Sand Cleaning – Mechanisms of Mechanical Scrubbing (B-FSM-140)

The cleaning system we will detail in this module is designed around mechanical scrubbing. It is a compact package specifically targeting offshore oil & gas facilities.

Mechanical scrubbing to remove adsorbed oil from sand particles takes place through three concurrent mechanisms.

Shear – High velocity water interacting with particles to physically shear oil from the sand particle

Abrasion – Impact of the oil coated sand with the cleaning equipment (i.e. pipe wall, valve components, pump parts, and cyclone internals).

Attrition – High concentration of sand particles in a slurry interacting with each other, where the interaction physically scrubs oil from the surface of the sand particles

References:

  1. Rawlins, C.H. and Wang, I. 2001. “Design and Installation of a Sand-Separation and -Handling System for a Gulf of Mexico Oil Production Facility”. SPE Production and Facilities, August, pp. 134-140. https://doi.org/10.2118/72999-PA
  2. Rawlins, C.H. 2019. “Enhanced Production Through Surface Facilities Sand Management.” SPE Distinguished Lecturer presentation. Link here

Next week I will continue discussion on cyclonic sand cleaning system design.

Sand Cleaning – Oil-on-Sand Analysis (B-FSM-139)

SiteLab® kit uses UVF method (www.site-lab.com)

  • TPH, GRO, DRO, and PAH
  • Comparable to EPA SW-846
  • 05-0.5 ppm or to 50,000 ppm
  • MDL of TPH in soil = 0.54 mg/Kg

Procedure:

  • Extract soil sample in solvent
  • Methanol or Turner OIW surfactant
  • Filter to remove particles
  • Dilute and measure in UVF device
  • Five minutes per sample

Or, use on-site produced water OIW methods and equipment

  • Will need on-site analysis to tune and monitor sand cleaning system

References:

  1. Rawlins, C.H. and Wang, I. 2001. “Design and Installation of a Sand-Separation and -Handling System for a Gulf of Mexico Oil Production Facility”. SPE Production and Facilities, August, pp. 134-140. https://doi.org/10.2118/72999-PA
  2. Rawlins, C.H. 2019. “Enhanced Production Through Surface Facilities Sand Management.” SPE Distinguished Lecturer presentation. Link here

Next week I will start discussion on cyclonic sand cleaning system design.

Sand Cleaning – Oil-on-Sand Calculations (B-FSM-138)

What is thickness of oil layer on “cleaned” sand?

  • OSPAR regulation of 1 weight percent oil on dry sand (10,000 mg/kg)
  • Basis: ρs=2650 kg/m³, ρo=904 kg/m³ (API 25)

Step 1: Convert 99 wt.% sand to volume fraction (c):

Step 2: Calculate aggregate density:

Step 3: Calculations for 100 µm sand particle:

  • Oil Thickness Layer = 52 µm on 100 µm sand particle, or 0.26 µm on 50 µm sand, or 0.05 µm on 10 µm sand
  • Volume of oil in layer = 5 µm droplet

References:

  1. Rawlins, C.H. and Wang, I. 2001. “Design and Installation of a Sand-Separation and -Handling System for a Gulf of Mexico Oil Production Facility”. SPE Production and Facilities, August, pp. 134-140. https://doi.org/10.2118/72999-PA
  2. Rawlins, C.H. 2019. “Enhanced Production Through Surface Facilities Sand Management.” SPE Distinguished Lecturer presentation. Link here

Next week I will cover oil-on-sand analysis.

Sand Cleaning – Oil & Gas Sand Cleaning Defined (B-FSM-137)

Definition: Remove adsorbed oil layer from produced solids using mechanical scrubbing in a compact system primarily for offshore use.

  • Minimal footprint and weight (cyclonic technology)
  • No or minimal chemical use (solvents or surfactants)
  • Minimal energy use (e.g. heat addition)

Uses combination of mechanical forces:

  • Shear: liquid-particle interaction
  • Abrasion: particle-wall interaction
  • Attrition: particle-particle interaction

Oil attachment to sand particle

  • Oil can attach to sand particle in many different ways as illustrated in graphic above

References:

  1. Rawlins, C.H. and Wang, I. 2001. “Design and Installation of a Sand-Separation and -Handling System for a Gulf of Mexico Oil Production Facility”. SPE Production and Facilities, August, pp. 134-140. https://doi.org/10.2118/72999-PA
  2. Rawlins, C.H. 2019. “Enhanced Production Through Surface Facilities Sand Management.” SPE Distinguished Lecturer presentation. Link here

Next week I will cover oil-on-sand calculations.

 
 
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