Cutting operations are performed for a variety of reasons, such as plug and abandonment, pipe recovery, or as in this case for a tubing cut in preparation for a sidetrack operation.

In some cutting operations an explosive method can be utilized whereby a charge is placed downhole and detonated to create the desired cut. However, this method is not without its drawbacks, as the explosion cannot provide pinpoint accuracy and could damage outside tubing/casing beyond the desired cut. Additional logistical issues related to the transport of explosives can also make the method less desirable.

In this case, a large International Oil Company (IOC) needed to perform a tubing cut in preparation for a sidetrack operation. A mechanical non-explosive cutter was the desired option due to the abovementioned risks and need for a high-level of accuracy.

A 358 Well Cutter® was selected due to its ability to provide a controlled and precise cut, with no risk of damage to the outside tubing. Additional modifications made to the tool also enabled an increase of the cutting pressure to a level capable of cutting an incredibly tough 5 ½” 17 PPF 25CR-125ksi tubing.

Preparation

A Systems Integration Test (SIT) was performed to assess the initial capability of a 358 Well Cutter against the 5 ½” 17 PPF 25CR-125ks tubing.

As a result, the Well Cutter was modified to increase cutting pressure, and subsequent testing confirmed that it would be able to perform the tubing cut.

Despite the cutter being non-explosive, and with the ability to control cutting depth, the IOC expressed some concerns over the possibility of damage occurring to the casing following the tubing cut. To alleviate those fears, Welltec proposed restricting the opening of the machining arms to only 5.86”, which would prevent any further extension and remove any risk of even a scratch to the casing.

In operation

The 358 Well Cutter was run in hole and reached target depth without any hold up, and the engineer on board performed the correlation along with the wireline engineer.

Once the depth was confirmed and agreed by all parties, the Well Cutter was activated at 5,564 ft. With a clear indication of contact, the cut was carried out and within 15 minutes surface read-outs indicated a successful cut – the tool was powered down and pulled out of hole.

At surface, the engineers on board checked and confirmed the maximum cutter opening at 5.86”, thus providing a further confirmation of success.

The operation was performed at the first attempt without issue, and enabled the client to secure the well prior to sidetracking without risking any damage to the well casing (normally associated with explosive cutters) – which could have led to scenario where plugging the well was not possible.

The tubing cut was performed with pinpoint accuracy and to a predetermined size. The ability to precisely control the Well Cutter meant that Welltec was able to fully address the IOC’s operational concerns. In addition to providing a non-explosive mechanical solution, Welltec further safeguarded the operation by limiting the cutter opening.

Following the success of this operation, Welltec was designated as the primary provider of mechanical cutting solutions for the remainder of the campaign’s second phase, which would involve a total of six wells.

The IOC was extremely pleased with the end result of “A seamless and safe execution of a Christmas tree tubing cut and completion string removal.”