When Maersk Oil relegated the Kola Superdeep Borehole to second position in the longest well ranking, by reaching a drilling depth of 12 280 m

(40 300 ft) back in 2008, the first downhole swivel dedicated for string deployment operations had been commercialised for less than 2 years and barely counted a 15 runs history.

Running further than

beforeNicolas Sluys, Rubicon Oilfield

International, UK, explains how swivel tools are aiding the completion of longer

extended-reach drilling operations.

| Oilfield Technology Reprinted from June 2019

In April 2015, a new record was set at 13 500 m (44 290 ft) on Sakhalin Island, Russia, which marked the 305th run of the SwivelMASTER suite of tools. That number has since grown exponentially and the tools contributed to the successful completion of the current longest extended-reach well on the same field, which measures at a depth of 15 000 m (49 210 ft).

This rapid increase in downhole swivel runs can be explained by ever-improving drilling practices and technologies, which allow the achievement of longer step-outs. The expansion of drilling boundaries comes with the inherent requirement for specialty deployment tools, which allows efficiently run liners and lower completions to target depth, thus maximising the return on investment.

Deployment challenges in extended-reach drillingIt is well understood that conventional deployment of liners and lower completion strings quickly show their limits in extended-reach drilling (ERD) wells, as the encountered drag leads to buckling and surface weight issues, not to mention the inability to smoothly transfer weight through the landing string. Rotation is key in these applications, as the addition of another source of energy in the system splits the downhole friction between torque and drag (the ratio between the tripping in hole and rotational speeds dictates how much of the friction is converted from drag to torque). The result of tripping in hole with rotation is a better controlled weight transfer and a substantial drag reduction ability which reduces the likelihood of buckling.

However, the downside is that the torque required to rotate the long string in extended-reach applications often reaches the system’s limitation, whether it is driven by the pipe connections or the top drive output. Several factors, such as premium connection cost, fatigue concern, and sensitive lower completion equipment, have caused most operators to stay away from full string rotation. As a result, the drill pipe deployed SwivelMASTER was developed to decouple landing string rotation from the lower string, providing drag reduction benefits while preventing any torque being transferred to the lower sensitive equipment.

Some could argue that rotation does predispose the string to helical buckling but modelling and field experience both show

that the reduced axial load applied on the string from the drag reduction mostly overcomes this risk. In addition, the substantial drag reduction gained through rotation allows for stiffer pipes to be run at locations within the landing string where the expected compressive loads are the highest. This has enabled a complete redesign of the landing string configuration on some applications, moving away from the historical tapered string setup used when deploying non-rotatable lower strings.

Deployment downhole swivelThe SwivelMASTER tool features heavy-duty bearings that are capable of pushing and pulling high loads for extended periods, at rotational speeds of up to 80 – 100 rpm. A hydraulic clutch, triggered through pressure differential, can permanently lock the tool at total depth (TD) to allow for the contingency mechanical release of the service tool if required. The swivel conversion pressure is simply set by adding or removing shear pins while the string is pressurised using the liner hanger/packer setting ball, meaning that no time is lost converting the tool.

The dual bearing system has shown its added value when string reciprocation is required to help work the string past ledges and to allow higher overpull in differentially sticking-prone environments. The bespoke clutch is designed to exceed the drill pipe high torque connections and allow for enough torque transfer through the lower string for contingency situations. Furthermore, the simple and robust design moves the weak point in the string away from the swivel.

Engineering developmentsThe swivel tool is still often considered by operators as insurance, with wells designed to allow for conventional pipe deployment, but keeping the landing string rotationability as a contingency allows for options should the downhole condition be more challenging than expected. Thus, the SwivelMASTER is increasingly being considered as an integral part of the deployment strategy by operators in an attempt to consistently access longer and previously unreachable pay zones. This has led Rubicon to work with many engineering projects to increase their operating envelopes, and provide fit-for-purpose variations as well as developing new swivel-based systems.

Figure 1. The SwivelMASTER provided 109 000 lbs of additional weight in a challenging pre-perforated liner deployment.

Reprinted from June 2019 Oilfield Technology |

Successive bearing upgrades have been performed over the years with the latest target being to reach a 220 000 lbs load on bearing for 24 hr at 80 rpm. This will enable longer and heavier lower strings to be run in hole.

Product tiering has seen two new tools being successfully field tested in the last 6 months, the first one being a clutch-free design with a lower wall thickness that has been designed for clean-up and logging operations. The tool allows the landing string to spin, which improves the fluid and cutting displacement without damaging the clean-up tools. When used on logging applications, the landing string reduces the axial stick slip and improves the logging quality.

The second field validation was a mechanical clutch variant of the hydraulic SwivelMASTER. The same bearing technology is fitted in the tool, but the piston type clutch is replaced by an overrunning clutch which maintains the tool in swivel mode to the right but transfers torque to the left at all times. On its fifth run offshore in Norway, the tool allowed swivelling to be performed over the last 2540 m section of the wellbore to successfully land the screens completion to a field record of 8500 m measured depth.

Longer development projects have also taken place. The casing-based swivel was successfully qualified in 2015 and more than 30 tools have been sold to date. The purpose of the tool is to extend the portion of the rotating string to the upper section of the liner and to provide extended drag reduction without exceeding the connection’s limitations. The complexity of the tool lies in the requirement to meet the casing specifications while keeping a large enough drift. The CasingSWIVEL was involved in the longest single stage 6 5/8 in. liner deployment in UAE in 2017 (SPE-188323-MS).

The latest large-scale engineering project was the development and full tool in-house testing of a drill pipe swivel tool that – unlike the deployment type SwivelMASTER – can handle the drilling environment’s challenges. The TornadoSWIVEL was developed in response to the inability to run jars in ERD wells due to the lack of available downhole force. The tool is run in the locked mode, transferring torque to the bottomhole assembly (BHA), and should a stuck pipe event occur it is hydraulically converted into the swivel mode to allow enough force transfer for the jar to be fired. The tool can function multiple times from lock to swivel and vice versa through pressure differential using a simple J-slot system. A proprietary stackable large-bore dart sub-system has also been tested to provide the required pressure differential without interfering with other BHA equipment.

A combined approachAs Rubicon was integrating multiple companies to complete its well construction and intervention portfolio, the opportunity presented itself to combine technologies and start thinking more out-of-the-box. The RotationABILITY concept that resulted has been designed to provide the ability to initiate selective rotation to overcome current challenges throughout the well tubular deployment. The concept has been put together to understand and identify how selective rotation of the string, through the use of downhole swivels, can improve the operations efficiency from the well construction side to the well intervention and abandonment.

The foundations of the concept rely on the strong deployment enhancement background and experience obtained over the 730+ SwivelMASTER runs. Both the products’ and

applications’ engineering competencies were key in allowing Rubicon to become a reliable partner for operators on the deployment side. The field of applications, which primarily started with liner and screens deployment, was already expanding using the SwivelMASTER alone and witnessed rotationally set packers being run, ball drop efficiency increasing, TCP guns being pulled out and river crossing projects completed.

Combining the CasingSWIVEL with external casing packer (ECP) and differential valve (DV) tools opens the door to a game-changing improvement in stage cementing efficiency, as rotation of the upper section is now becoming available. With the legislation regarding sustained annular pressure becoming stricter, the requirement for proper zonal isolation is even more critical than before. Cement is now considered to be an asset and more emphasis on proper cement bonds is expected to occur as the financial incentive keeps growing. Being able to rotate the casing/liner during second stage cementing could become the standard practice in the near future.

Coupling the drilling TornadoSWIVEL with a speciality reaming tool on top of the BHA allows – once the swivel is unlocked – the landing string and reamer to be rotated at a much higher speed than they can today during back-reaming operations. The main limiting factors when back-reaming is the risk of backing off the connection, should the string stall, and the risk of damaging the expensive downhole equipment including rotary steerable system (RSS), logging while drilling (LWD) and measurement while drilling (MWD) as the loss of the contact point at the bit increases the lateral instability of the BHA. Decoupling the landing string rotation from the BHA not only increases the back-reaming operation efficiency by mitigating the connection back-off at high speed, but significant savings are also expected in downhole tools repair costs.

ConclusionThe ability to rotate the landing string when deploying liners and lower completions in high step-out wells has proven highly valuable in ensuring target depth is successfully reached on the first attempt.

While having been performed on the major ERD playfields over the years, the use of the SwivelMASTER as a deployment enhancement system is being promoted to new areas including Alaska and California with strong results. The total number of runs has significantly increased over the last 2 years, breaking many records, including the longest well completed and longest single stage 6 5/8 in. liner deployed to date.

The robust design of the tool coupled with Rubicon in-house engineering capabilities has created solid foundations for the new RotationABILITY concept. This concept promotes the use of downhole swivels throughout the entire well lifecycle in order to improve the operational efficiency through selective rotation.

The integration of the CasingSWIVEL as a selective cementation device is expected to change the stage cementing landscape in the coming months, by allowing casing and liner rotation while cementing in applications where it cannot currently be performed due to system and operational limitations.

The percentage of complex ERD wells is expected to keep increasing in order to optimise the reservoir exposure and access remote pay zones. With this in mind, there is a need to continue developing downhole swivels that allow successful completion of the wells.