With rig day rates only increasing, operators are now placing more importance on finding alternative methods to decommission ageing assets to drive efficiency savings. Rigless abandonments are nothing new, in fact, Claxton performed the world’s first rigless platform well abandonment campaign on the Esmond, Forbes and Gordon field over 20 years ago. However, in recent years we have seen an increased demand for combined platform and jack-up lift barge (JULB) operations. This blog, which is part of our new decommissioning series, explains how a jack-up lift barge can be utilised to realise time and cost savings whilst increasing efficiency.
HOW DOES A JACK-UP LIFT BARGE WORK?
A jack-up lift barge, much like a traditional rig, has long support legs that can be raised or lowered. The barge self-propels with its legs up and its hull floating on the water, and once on location, the legs are jacked down onto the seafloor. JULBs offer great flexibility and are generally used for construction, maintenance, accommodation and well services including well abandonment.
JULBs are designed to withstand harsh offshore environmental conditions and can operate in water depths of up to 60 meters all year round. Available in a wide variety of sizes and capabilities, you can expect deck areas greater than 900m2, cranes approaching 400Te and places on board exceeding 100. These features combined make JULBs the cost effective mobile platform for well intervention.
CONVENTIONAL JACK-UP RIG VS. JACK-UP LIFT BARGE
A jack-up rig and JULB are both mobile offshore units which share the same jack-up methodology, with the main aesthetical difference being that a jack-up rig has a cantilever and derrick, although some JULBs are now able to deploy a cantilever. Both are usually highly robust self-elevating units which raise and lower above the water level on jacking legs. They can be manoeuvred over water into a working position to provide a stable, safe working platform, however there are some water depth limitations, more so with the JULB. A JULB is best suited to shallow water operations, up to 60 meters, whereas a jack-up will withstand up to 120 meters.
Generally, conventional jack-up rigs are not self-propelled and rely on tugs or heavy lift ships for transportation, adding to the costs of the project. Towing a rig over long distances is slow so, for long trips, jack-ups can be loaded onto a heavy-lift ship. The JULB has the advantage of being self-propelled, meaning that mobilisation can happen, and operations can begin before a jack-up rig would even arrive at the location. The JULB has the added advantage of being able to move from platform to platform, performing multiple well abandonments in an efficient and cost-effective manner.
Due to well conditions, some projects will naturally need a conventional rig, however, where time, money and deck space are at a premium, a jack-up lift barge has the upper hand because it can be rapidly mobilised at a lower cost to support a wide selection of cranes and other plant to meet project specific requirements.
Both JULBs and jack-up rigs have high pulling/lifting capacity provided by cranes or the derrick, with the main crane on a typical JULB having approximately 200-400 tonne capacity and the port and starboard cranes can lift in the region of 45 tonnes.
Deck load capacities can vary from rig to rig but as an example, the typical JULB will take up to 5,000 tonnes, with the equivalent jack-up rig only having a slightly higher capacity. There are some jack-up rigs available for North Sea use, which do have a variable deck load up to 10,000 tonnes, however, this type of unit can only be commercially competitive in the North Sea and in very special situations. These types of rigs are geared towards deeper waters, whereas JULBs are best utilised in shallow water where a lower capacity is required. This makes a JULB ideal for some of the smaller platforms, particularly in Southern North Sea waters.
HOW A JACK-UP LIFT BARGE CAN HELP OVERCOME DECK SPACE CHALLENGES
When platform deck space on a decommissioning project is at a premium or the structural integrity of the asset is in question, a joint platform and JULB based recovery operation may be required. In this scenario the JULB acts as the mothership, housing all the necessary equipment, only running services and the required tooling to the platform deck. It is also worth noting that the speed of transit and ease of setup on location means that using a JULB opens the opportunity for innovative multi-operator campaigns, which when combined with bespoke tooling can achieve a highly efficient solution.
Combined tubing recovery operations, based on a dual recovery operation between the platform and a jack-up lift barge, is one approach which has been proven by Claxton on projects with limited deck space. If there is a requirement to skid across numerous well slots, there is scope for bespoke equipment to be developed. For one project Claxton worked on, a light weight recovery deck was designed to provide a work platform and load bearing structure to span and react against the platform deck beams during recovery operations. During the recovery process, the JULB crane provided the means of lifting with the light weight recovery deck acting as a false rotary. What’s more, Claxton have also provided an engineered solution to speed up the tubing recovery by utilising an innovative tubing lay down system.
During well recovery processes on small platforms, the Xmas tree can be lifted clear of the well using the JULB crane and transferred into a container on the JULB main deck ready for back loading. Once the conductor/multi-string casing has been elevated to the required height and drilling and pinning has taken place, bandsaws can cut the casings to manageable lengths prior to transfer to the deck of the JULB ready for backloading. This is an example of how Claxton’s decommissioning platform package works in harmony and adapts to whatever assets are available to the client.
CLAXTON PROJECTS WHICH HAVE OPTIMISED JACK-UP LIFT BARGES
Claxton’s subsea abrasive cutting system (SABRE™) has been proven to run off a JULB. Three project examples can be found below:
- When Tullow Oil approached Claxton about the well abandonment of the Horne and Wren Platform in the Southern North Sea the technical challenges arising from the absence of a rig, limited crane facilities on the platform, the small 8m x 8m weather deck, and the use of a JULB were quite unique. The size of the platform is one of the smallest of its kind in the sector so the scope of work to mitigate the challenges faced is not something many can help with. Completed within 18 operational days, Claxton was responsible for the 5.1/2” tubing cut verification, tubing recovery, sub-mudline abrasive conductor severance, conductor cut verification and the subsequent multi-string recovery from the two wells. Read more.
- An operator wanted a safe and cost-effective way to decommission a well in Morecambe Bay in the Irish Sea. Traditionally, this work scope, which included cleaning and dredging the well, placing cement barriers in the bore and cutting and recovering the casing, would require the use of a rig. However, the client wanted a safe and efficient solution that could be deployed from its existing JULB. Critically, Claxton’s specialist tools and deployment equipment enabled the use of the relatively small JULB . Read more.
- As part of their wider decommissioning programme in the Southern North Sea, a client called on Claxton to abandon seven platform wells, plus one abandoned tieback well, across their two platforms. The client agreed that combined tubing recovery operations, based on a dual recovery operation between the platforms and a jack-up lift barge, would be the best approach due to limited deck space. This removed the need for a drilling rig. Claxton’s experience has proven that this is a great way to decommission the smaller aging platforms in the North Sea. Over the years Claxton have built up a large array of relevant tooling that sets us apart from our competitors in this method of decommissioning. Read more.
THE RIGHT SOLUTION FOR YOUR PROJECT
The main takeaway from this blog is to ask yourself ‘is a rig required or can you utilise more cost-effective assets?’ Yes, jack-up rigs have advanced and refurbishments are seeing them become more robust, but if there is not a requirement for deeper water capacity or more complex P&A scopes, why pay for assets which are not required?
Here at Claxton we provide rig-based, rigless and JULB end to end recommendations and execution for decommissioning projects, along with bespoke tooling. All our projects tend to be unique so ultimately it is the client’s choice as to which route they go down based on the advice we provide. The decision is often based on what equipment the client already has available, the budget at their disposal to invest in other equipment, efficiencies they can make by using different techniques, and the timescales in which they need to complete the project in.
We have recently adapted our decommissioning offer at Claxton, which is supported by a new technology and people strategy. Claxton understands that every job and offering has a large bespoke aspect, so solutions can be unique. We can’t stand still in what is a changing market and aim to continue to define rigless and rig-based decommissioning moving forward. Find out more about our re-energised decommissioning team on our recent blog.
Look out for the next in our series of decommissioning blogs, and if there is a particular subject you would like us to cover, please leave your thoughts and feedback below…