Schlumberger

Case Study: Western Canada: Shaker Technology Reduces Airborne Exposure to OBM Contaminants

Challenge: Worker exposure to oil-base drilling fluid has been recognized as a major HSE concern. The base fluid and additives of an oil-based mud (OBM) typically are selected based on the wellbore stability and other performance benefits they deliver compared to water-based drilling fluids. Thus, while substituting an OBM with a water-based mud (WBM) may be impractical from an operational perspective, the use of less toxic base oils should be considered when practical. However, it’s important to keep in mind these less toxic base oils often are lighter and can result in more mist. Further, the use of engineered controls to reduce exposure should be examined as an alternative.

High exposure risks for airborne vapors and mists are near areas where the fluid is highly agitated, such as at the shale shakers. Studies have shown that OBM drilling operations in the vicinity of the shakers generate oil mist and other airborne contaminants in excess of occupational exposure limits (EL). While effective controls are available to protect workers from harmful exposure, a combination of control measures will be required to achieve this objective. The industry must commit to being diligent to select the most effective control technologies available, and to ensure the best practices are followed at drilling sites.

Solution: Respected Western Canada contractor, Stoneham Drilling, had concerns for its workers and asked M-I SWACO for ways to reduce this exposure. M-I SWACO recommended the operator pilot test the MONGOOSE shaker equipped with a vent hood for its drilling operation outside Grande Prairie, Alberta. The MONGOOSE with a vent hood was seen as the most readily available engineering control to reduce worker exposure at the shakers, which have been identified as a key area where worker exposure can occur by inhalation, skin contact or ingestion.

Result: The implementation of effective exposure controls is the result of risk assessments and evaluations. Most Occupational Health and Safety (OH&S) Regulations require employers select controls based on the following hierarchy:

  • Substitution
  • Engineering controls, such as local exhaust ventilation, barriers
  • Administrative controls, including limiting the time workers are in a potentially contaminated area and
  • Personal protective equipment (PPE), including respirators and disposable coveralls

Typically, the use of engineering controls is the most desirable and effective. Personal protective controls should be considered only when engineering controls and/or administrative controls are either not practical or ineffective on their own. For the targeted operation, an independent party conducted occupational air sampling at Stoneham Rig 19 drilling near Grande Prairie, Alberta. Sampling was conducted to compare exposure to benzene, toluene, ethyl benzene, xylene (BTEX), total hydrocarbons (THC), and oil mist with the vent hood off and on the shaker.

Test results with the hood on the shaker were significantly less than those with the hood removed. With the vent hood on, the oil mist concentration at the four sample points ranged from 0.00-0.22 mg/m3. The MONGOOSE shaker equipped with the vent hood reduced exposure by 50 percent and fell below the AB 8-hour OEL.


Download: Western Canada: Shaker Technology Reduces Airborne Exposure to OBM Contaminants (0.62 MB PDF)

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Overall I feel the vent hoods greatly reduce the exposure to hydrocarbons for the men working around the mud tanks and as an added benefit, the mud tanks and the rig stay a lot cleaner as there is hardly any invert mist floating in the air.
Darin Ramsell
Operations Superintendent
Stoneham Drilling