Operators have established best practices to minimize the risk of contaminating freshwater and hydrocarbons during the wellbore construction process. One such practice involves rotating the casing string while cementing to improve cement bond quality. While this procedure is proven to substantially improve cement integrity on a primary cementing job, the adoption rate among operators remains at about 10%. The limitations to broader adoption are likely equipment-related; therefore, operators should expect the latest cementation tools to incorporate decades of lessons learned.

A primary consideration when introducing new equipment and processes is the need to minimize safety-related risks. Early equipment proved to be bulky and labor-intensive to convey and rig up. A future solution will need to address these operator concerns:

  • Does it reduce the need for human interaction and eliminate personnel from the red zone?
  • Does it work with established best practices such as the ability to rotate and reciprocate casing during cementation?
  • Does it reduce the flat time that conventional methods and legacy equipment have not been able to overcome?
  • Will it work on existing rigs and the new breed of rigs currently being developed?

First-generation launchers

The execution of early cementing operations used a cement head with manually loaded plugs and the manipulation of multiple valves. The transition from running casing to rigging up of cementing equipment often required one to two hours of flat time.

Tesco’s first solution to combat flat time used the Casing Drive System (CDS) in conjunction with a cement swivel and plug assembly to reduce transition time by up to 75%. While this configuration reduced transition time, it could not accommodate the increasingly diverse array of plug arrangements the market was offering. To mitigate safety concerns and uncertainty while applying best practices, manufacturers developed cement heads with integrated chambers to house plugs and simplify the launching procedure. These new cement heads had an alternate flow path but still required manual launching of plugs. Depending on the height of the cement head assembly, a technician would need to be lifted in a basket or harness to initiate the release.

Early systems often exceeded 12.2 m (40 ft) in length, limiting use to only the largest land or offshore rigs. Operator feedback led to further enhancements such as viewing ports, launch indicators, and mechanical or automated launching systems. Few attempts, however, were made to reduce the overall size.

One feature often requested was the need for visual indication that a plug was launched. Incorporating a “tattle-tale” indicator on the plug chamber enables visual confirmation that the plug was released, but there was still the possibility of plugs getting stuck before entering the casing. Multiple “tattle tales” were requested to show that a plug not only left its starting position but that it did not become lodged at the bottom of the launch mechanism before entering the casing. There also needed to be a fail-safe way to enable manual launching if the automated or mechanical release mechanism failed.

Another issue with initial designs was the inability to load plugs onsite without the need for a bucking unit or breakout vise. This posed a risk to operators because they could not verify that the correct plugs were loaded in the precise orientation if assembled offsite. If there were last-minute changes to the scope of the cement job, the tool could not be easily serviced onsite. Sending the equipment back to the shop would be cost-prohibitive, especially in remote locations.

As plug technology continued to advance, containers that housed them needed to follow suit. Plug designs began to get longer, yet operators wanted a more compact launching system that could be used on smaller land rigs.

Modular design

In response to operator feedback, the Multi-Plug Launching System (MPLS) was developed and brought to market by Tesco to address the concerns regarding current plug launchers. The standard MPLS configuration measures less than 92 in. and is capable of launching two plugs up to 20 in. each or a single plug up to 38 in. This design enables a more cost-efficient operation and faster rigup times while reducing safety concerns when compared to a conventional cement head or larger plug launchers.

The system’s modular design enables adaptation for future plug design and cementation programs when more than two plugs are requested. Additional plugs can be accommodated by adding chambers to the unit. Plug loading is completed in the shop prior to being sent to the location, yet the design allows quick disassembly onsite without the need for a bucking unit.

The MPLS has wireless launch capabilities, enabling personnel to use the system from a safe distance outside of the red zone. Levers at each plug-release port double as a visual indicator and as a manual override. An indicator sub below the MPLS confirms the plug has exited the tool and entered the casing. Most importantly, when the system is combined with a cement swivel, the rotation and reciprocation of the casing while cementing is possible.

Field successes

The system is about 4.6 m (15 ft) shorter than other multiple-plug systems available, even with the cement swivel and optional safety valves. During testing, the shorter length enabled a major operator in the Marcellus Shale to reciprocate its production casing 4.6 m while performing cementing operations. Operators that use trailer-mounted super-single rigs with masts of 23 m (75 ft) can reciprocate about 3 m (10 ft), enabling improved primary cementing quality and reducing the nonproductive time (NPT) associated with remedial cementation or squeeze jobs. This is an important benefit provided by the MPLS because taller equipment stack-ups cannot fit within the mast or lose the ability to reciprocate.

A major operator in East Texas was cementing the production string in a horizontal section of its well and used Tesco’s TesTORK in conjunction with the MPLS to calculate the precise torque profile during rotation. By monitoring the torque throughout the process, the operator ensured no added stress was placed on the connections.

The MPLS is designed to work as a standalone system, with an additional value realized when used with the CDS for casing running operations.

What kind of real-world value can operators expect to receive from a 15% increase in cement jobs that incorporates rotation and reciprocation? The Freedonia Group estimated in April that 4,255 wells would be drilled in the Permian Basin in 2017. There are three assumptions made regarding wells in this area. One is that three casing strings will require cementation. Another is that operators will spend 1.5 hours transitioning from casing running to cementation using conventional equipment. The third is that the rig’s day rate is $14,600, according to a Platt’s report from April. If 25% of these wells utilize rotation and reciprocation, operators can save as much as 133.625 days of NPT or $1.9 million per year. These significant savings arise solely out of reductions in rigup time and do not include the time that would have been used for remedial cement jobs.

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