Eliminating exposure to naturally occurring radioactive materials (NORM) with closed-loop dual cyclone desanders
Bergen, Norway, November - 2024
Energy operators have made significant strides over the last decade to reduce health, safety, and environmental (HSE) risk by leveraging advancements in automation and digitalisation. However, there are still many hydrocarbon production-related activities whose safety can be drastically improved by upgrading legacy technologies and workflows.
By Olof Nilsson, Marketing Manager, FourPhase
In the context of sand management, worker exposure to naturally occurring radioactive material (NORM) and other hazardous chemicals (e.g., H2S gas, Benzene, etc.) has broadly been accepted by the industry as an unavoidable part of operation.
Traditional methods of sand removal typically rely on the manual transfer of sand from the production separator vessel to skips, where it is stored and disposed of from the platform. This can potentially expose offshore operators to hazardous substances across multiple sand-handling scenarios.
Using automated desanders that flush both to and from closed tanks offers a solution to this longstanding problem. In such systems, NORM and any other hazardous chemicals can be produced to the surface without exposure to workers, enabling 100% hands-free solids removal.
By Olof Nilsson, Marketing Manager, FourPhase
In the context of sand management, worker exposure to naturally occurring radioactive material (NORM) and other hazardous chemicals (e.g., H2S gas, Benzene, etc.) has broadly been accepted by the industry as an unavoidable part of operation.
Traditional methods of sand removal typically rely on the manual transfer of sand from the production separator vessel to skips, where it is stored and disposed of from the platform. This can potentially expose offshore operators to hazardous substances across multiple sand-handling scenarios.
Using automated desanders that flush both to and from closed tanks offers a solution to this longstanding problem. In such systems, NORM and any other hazardous chemicals can be produced to the surface without exposure to workers, enabling 100% hands-free solids removal.
What is NORM in the context of oil and gas?
NORM originates from the natural decay of radioactive elements, such as uranium and thorium, which are common in varying concentrations in subsurface geological formations. The hazardous elements found in NORM include radium 226, 228 and radon 222, as well as daughter products from these radionuclides.
During oil and gas production, solids containing NORM are brought to the surface and can accumulate in equipment and/or produced sands.
NORM levels are dependent on numerous variables and can vary greatly from well to well. The radioactive isotopes build and radiate differently depending on the reservoir rock and salinity. Because salinity tends to increase with age, older wells frequently carry a greater risk of NORM than younger wells. With less greenfield developments and an increasing base of brownfield assets the industry needs better solutions for managing NORM.
Converting the concentrations of NORM into operator exposure levels also depends on several factors. For reference, the Norwegian limit for NORM exposure is set to 7.5 mSv/h. If exposure exceeds this level, it is recommended that the work area be closed off to limit access.¹
H2S gas, benzene, and other volatile organic compounds (VOCs) can also be present in high concentrations during sand removal activities. It is incumbent on operators to test for the presence of these compounds and, where possible, to implement measures that limit (or ideally eliminate) any human exposure risk.
During oil and gas production, solids containing NORM are brought to the surface and can accumulate in equipment and/or produced sands.
NORM levels are dependent on numerous variables and can vary greatly from well to well. The radioactive isotopes build and radiate differently depending on the reservoir rock and salinity. Because salinity tends to increase with age, older wells frequently carry a greater risk of NORM than younger wells. With less greenfield developments and an increasing base of brownfield assets the industry needs better solutions for managing NORM.
Converting the concentrations of NORM into operator exposure levels also depends on several factors. For reference, the Norwegian limit for NORM exposure is set to 7.5 mSv/h. If exposure exceeds this level, it is recommended that the work area be closed off to limit access.¹
H2S gas, benzene, and other volatile organic compounds (VOCs) can also be present in high concentrations during sand removal activities. It is incumbent on operators to test for the presence of these compounds and, where possible, to implement measures that limit (or ideally eliminate) any human exposure risk.
Enabling hands-free solids processing with closed-loop cyclonic desanders
A common sand removal system offshore for well services equipment entails a rudimentary desander that periodically unloads sand into a vessel by means of manual valve manipulation (the vessel is commonly referred to as a “Thunder box”). When the Thunder box fills up, the crew then manually dig-out sand into skips and weigh it to determine the quantity of sand recovered. This introduces a “confined space” work environment, which potentially exposes personnel to NORM and other hazardous substances for extended periods of time beyond safe levels.
Fully closed-loop dual cyclone desanders, like FourPhase’s DualFlow system, solve this problem by ensuring that separated solids are automatically transferred from the desander into a closed skip or sand wash system. At no point is any manual handling of sand required by onsite personnel.
DualFlow is highly digitalised and leverages real-time sand data to enable tuning the well flow. By maintaining optimal flow rates, production can be sustained at a consistent level, avoiding drops in production from choking back the well. This maximises solids-free production, lowering the cost per barrel and enhancing production performance.
With the DualFlow, when the solids settle to the bottom of the closed vessel it is flushed to an external tank or skip. With sand in the tank, the excess flush water can be skimmed off the top and re-used. Skimming off in closed skips provides the added benefit of increasing the percentage of solids. This improves logistics and CO2 footprint by potentially lowering the number of skips shipped to shore, adding to the overall ESG score of the operation.
Additionally, on some platforms there is a possibility to use a cuttings re-injection (CRI) well for disposing of solids in a hands-free manner. CRI has been applied for solids management on some North Sea platforms with success. It has many advantages and should be considered when initially planning for solids management handling.
FourPhase has deployed several closed-loop desanding systems for customers across the globe, including in the North Sea and the Middle East.
Fully closed-loop dual cyclone desanders, like FourPhase’s DualFlow system, solve this problem by ensuring that separated solids are automatically transferred from the desander into a closed skip or sand wash system. At no point is any manual handling of sand required by onsite personnel.
DualFlow is highly digitalised and leverages real-time sand data to enable tuning the well flow. By maintaining optimal flow rates, production can be sustained at a consistent level, avoiding drops in production from choking back the well. This maximises solids-free production, lowering the cost per barrel and enhancing production performance.
With the DualFlow, when the solids settle to the bottom of the closed vessel it is flushed to an external tank or skip. With sand in the tank, the excess flush water can be skimmed off the top and re-used. Skimming off in closed skips provides the added benefit of increasing the percentage of solids. This improves logistics and CO2 footprint by potentially lowering the number of skips shipped to shore, adding to the overall ESG score of the operation.
Additionally, on some platforms there is a possibility to use a cuttings re-injection (CRI) well for disposing of solids in a hands-free manner. CRI has been applied for solids management on some North Sea platforms with success. It has many advantages and should be considered when initially planning for solids management handling.
FourPhase has deployed several closed-loop desanding systems for customers across the globe, including in the North Sea and the Middle East.
Conclusion: changing the status quo
Historically, the oil and gas industry has been very slow to introduce new technologies. Very often there is a reluctance to change old methods because the existing approach is familiar and part of the normal workflow. Sand management has not been immune to this trend. The use of decades-old technology, poor system designs and manual activities are still prevalent across the offshore sector.
Closed-loop dual cyclone desanders represent a step-change improvement from legacy technologies from both an efficiency and HSE perspective. Particularly in cases where there is a high risk of NORM or other hazardous substances in the produced sand, a closed-loop system should be considered to preserve the health, safety, and well-being of workers.
References:
¹ Offshore Norge
Closed-loop dual cyclone desanders represent a step-change improvement from legacy technologies from both an efficiency and HSE perspective. Particularly in cases where there is a high risk of NORM or other hazardous substances in the produced sand, a closed-loop system should be considered to preserve the health, safety, and well-being of workers.
References:
¹ Offshore Norge