ThinJackGAP is a recently released technology for supplying real-time (flange) gap data, whatever the method of flange separation, to minimize the likelihood of jamming the bolts on a bolt hole.

The company completed a platform christmas tree separation offshore West Africa where the previous method was taking in excess of three days while 14 adjacent wells were shut in. The process took less than 24 hours of critical path production time, bringing forward millions of dollars of production from high-producing wells.

Previously, conventional cylinder jacks were placed underneath the ends of a crucifix shape of “I” beams. However, the cylinder jacks started to bend the platform’s structural beams, so the method was abandoned after 70 tonnes of force.

The common element of most of the seized flanges that ThinJack separates is rust in the bolt hole annuli. This needs significant force to overcome, sometimes up to 500 tonnes, with the capability for more force than this depending on the area between the outside of the bolt holes and the flange circumference.

Technical challenges

In the U.S. Gulf of Mexico ThinJack separated well flanges to allow bolt replacement over a 27-month period. Bolts were internally corroded due to the combination of salt atmosphere and high wellbore temperatures from a deep gas reservoir. The platform decks were not strong enough to take bespoke manufactured jacking systems or conventional casing jacks, and alternative methods meant high engineering and installation costs for structural strengthening of the platforms’ main support beams.

While the company works with drillstring and drawworks to add a powerful push to the rig’s pulling power, ThinJack also separates seized well flanges when there is no platform or jackup rig. The ThinJack technology is standalone and immediately available. This is the context of the company’s recent frame agreement in Egypt that followed the successful completion of emergency work to assist with restoring water injection.

ThinJack also works in combination with platform-based rigs and cranes, which typically have a lifting capability of between 5 tonnes and 30 tonnes. However, they are used for loading and unloading supply ships and moving personnel baskets and unavailable for well flange separations.

In West Africa ThinJack was contracted to assist with a backlog of christmas tree valve replacements before a jackup rig moored up alongside a production platform. There are limited methods for safe and effective sideways or angular pulls to remove valve covers or bonnets. Servicing these internal christmas tree valves or well annuli is possible once these bonnets are removed with ThinJack services.

On this well deck pipes, shut-off valves, flanges, gauges and support beams obstruct personnel movement and line of site to the well flange. This is the ideal site for ThinJackGAP, with flange gaps displayed at the system operator, and avoids a long work shift to unstick an unnecessarily tilted and jammed flange. Even on less crowded well decks repeatedly climbing just one access ladder adds significantly to the flange separation time. (Source: ThinJack Ltd.)

Comparison with alternative methods

ThinJacks are both an order of magnitude thinner and more powerful than other flange spreading methods. They can be made to fit in gaps as small as 1 mm and deliver hundreds of tonnes of force safely and precisely to the right place. The most effective of the conventional flange spreaders needs a minimum 6-mm gap and delivers tens of tonnes of force.

Some traditional well flange separation uses platform or rig crews wielding hammers and crowbars and delivering several tonnes of force. Conversely, the ThinJack method minimizes the likelihood of injury to people and damage to well jewelry such as small-bore piping and pressure gauges from these various ad hoc methods.

Where there is sufficient flange gap, many operators cut flange bolts during well abandonment. Where the gap is a few millimeters, ThinJack increases the gap first. Removing cut bolts from the block before a new flange is installed might take several long shifts in addition to the bolt-cutting time. Once the bolts or studs are cut, they cannot be tightened up partway through the flange separation process. Also, bolts and studs might need to be refastened quickly when well barriers are less effective than anticipated.

Per well flange ThinJacks generally take between 2 hours and 15 hours online critical path time depending on the extent to which a flange is stuck together. While this might not seem especially fast, it is time-effective when the ThinJack method is used before other often futile techniques. In general terms the order of cost-resultant savings to the customer can vary between $100,000 per day up to tens of millions of dollars depending on the number of wells, the oil and gas production value, and the cost of an attendant drill crew and rig.

New technology

In October 2016 ThinJack delivered ThinJackGAP, giving real-time gap data for all flange separation methods including ThinJack services, conventional spreaders, cranes, drillstrings and drawworks.

Flange gaps are measured when pulling rusty bolts through rusty bolt holes, and this minimizes the likelihood of jamming the bolts or studs inside the bolt holes. Once the flange tilts and jams, the powerful flange separation technique from a drillstring and drawworks becomes an effective flange jamming system. Note that EOR well operations might replace an old christmas tree, tubing or casing spool on a 30-yearold well conductor that is no longer vertical, but the upward pull is vertical and the small difference in angle increases the likelihood of a flange jam.

Other gap measuring systems such as a handheld vernier mean the measurer needs to clamber around pipework and obstructions on a crowded well deck to measure the gap. There is limited, if any, line of sight to see conventional gap measuring tools from a distance.

This slows down the flange separation and, because of the near inevitable jam, increases uncertainty and frustration just at the point when a drill crew thinks that the flange is about to come free.

ThinJackGAP displays the gap at several points on the flange circumference next to the separation system operator, who might be several meters away from the flange. Where the difference in gap is more than several millimeters, the flange separation should stop and a remedial plan agreed upon so that no one is blindly jamming the flange and unsticking it during the long shifts that follow.

Offshore