Performing operations in offshore oilfields will typically be sensitive to weather conditions. Even more so for operations on floating vessels. Wind, waves and ocean currents will impose motions on the vessel, like heave, sway, surge, pitch, roll and yaw.
Floating vessels are designed to withstand and reduce the effect of these motions, but they cannot be avoided. Even newer vessels may have insufficient design and equipment for the weather conditions it should safely operate in. The result is significant operational downtime, Waiting on Weather (WOW), or unacceptable safety levels.
A high spec floating drilling rig today can demand a day rate in the range of USD 500.000, with supporting service vessels and crew coming in at double that. Increasing the operational weather window, in which safe operations can be performed, is a key objective for a drilling contractor, service company and their clients.
In this article we will explore solutions for controlling lateral movements during material handling in demanding offshore environments and what it takes to minimize non-productive time (NPT) in rig and vessel-based offshore operations.
Increasing the operational weather window
Waiting for Weather (WOW) translates directly to NPT, an unwanted expense for the drilling contractor operating the rig, and/or for the oil company ultimately footing the bill.
The operational window impacts performance of work processes onboard the rig. One of these operations are material handling operations. These operations are an important element in a variety of offshore operations on a drilling rig. Such operations involve moving heavy equipment, materials, components and supplies between locations on the rig.
Such operations are also identified as key areas of focus for preventing injuries to personnel, and damage to equipment and facilities. In a worst-case scenario, it can even lead to fatalities.
From a safety, operational and commercial perspective, managing material handling in various weather conditions is imperative.
An improved weather window means more efficient operations, less downtime and therefore less time on location. This translates directly into reduced emissions to the environment.
Suggested reading: How Can Tailormade XMT Handling Systems Improve your NPT
Various ways to influence the operating weather window exist. The rig design, vessel size, thruster capacity can be designed and constructed at the yard. However, most key parameters related to the rig-design are very expensive to modify after it’s delivered.
Fortunately, there are guiding and fastening technologies available to increase the operational weather window, and its productivity, for an existing vessel. These can be retrofitted to your rig or vessel without altering any of its fundamental architecture.
It can be implemented incrementally, with limited to no interruption to your operation. Furthermore, when considering the cost of downtime and WOW, the return on investment is high.
Preventing lateral movement – safe material handling
Arresting lateral movements while equipment is in a parked position or being relocated from one position to another, will enable safe operations in adverse weather and hence increase the operational weather window.
Below the drill floor, where BOPs, Christmas trees (XMTs) and other equipment are moved in and out of the open moon pool, is a good example of an area with numerous, critical material handling processes.
The guiding and fastening technologies that can be applied, are also supported by various degrees of mechanization/automation.
Suggested reading: How Tailored Moonpool Handling Systems Can Improve Safety (HSE)
Efficient guiding systems – some examples
The moon pool area should be carefully considered when evaluating safe material handling and rig movement in adverse weather conditions. There is a significant potential to optimize safety and operational efficiency by implementing proper guiding systems.
Below is a non-exhaustive list of some of these technologies/products;
- Riser handling systems
- Safe and efficient handling of Risers between shuttle and well center
- XMT/BOP handling systems with lateral guiding
- Overhull (OHG) and underhull (UHG) guiding.
- Remote operated, always secured and handled from storage position to sea (below UHG) and back.
- See our article How Can Tailored Fitted Xmt Handling Systems Improve Your Npt for illustrations and more information!
- BOP Test pipe handler Systems
- Remote operated (guided) handling and parking of test pipes
- Eliminates use of rig crane
- Increases weather window for BOP testing.
The upper and lower arms are telescopic and can raise/lower the pipe into the BOP located below.
- N-Line / DAT Riser tension handling and parking systems – STR Arms
- Remote operated handsfree handling and safe parking of riser tension cylinders.
- Mechanized connection to riser.
- No manriding operations required.
- Moon pool Multi-purpose cranes
- Remote operated. Running along rails in the moon pool.
- Rotation, tilting and telescoping, removes manual work and improves efficiency.
- Covering large areas of the moon pool.
Increasing safety and extending the operational weather window remains a priority in the offshore industry. However, surprisingly many vessels are equipped with inferior systems to arrest lateral movements during critical operations, Even on modern floating drilling rigs. This results in unnecessary WOW and subsequent loss of/reduced day rate.
Arresting lateral movements should be a focus area to secure equipment in parked position and while being moved between locations. Technology, with varying degree of mechanization and automation, is available to resolve these issues and will increase safety, efficiency, and your operational weather window.
Based on the day rates for drilling rigs being in the USD 500.00 region and that the cost for supporting vessels/services are two times that, the return on investment on such technology can be significant.
Increasing the operational weather window will also reduce the time required to complete the drilling operations on location, meaning less emissions to the environment.