Flexibility and modularity enable tailored solutions for challenging shale plays

BRETT SCHELLENBERG, Nabors Industries  

The pursuit of solutions that make operations faster, more efficient and more affordable is unending. As operational environments become more complex, and expectations for drilling performance continue to rise, drilling contractors and other service providers are developing innovative solutions to meet those challenges.  

This process is not new.  

Since the first wooden rigs were introduced, the industry has looked for better ways to work, from using steam engines and the first rudimentary casing to introducing top drives, installing catwalks, moving from DC to AC power, designing rigs that can walk, and adding higher pressure pumps.   

Higher performing assets are helping to address economic challenges, and new rig innovations are proving that the right rig capabilities combined with a dedicated, experienced field team is the critical ingredient for drilling success.   

UNDERSTANDING THE CHALLENGES 

The shift to unconventional drilling, which constitutes the majority of drilling operations in the United States, has introduced new challenges for drilling contractors and for the rigs that must perform much more exacting functions in complex unconventional environments while still delivering the reliable performance operators have come to expect.  

Unconventional drilling almost exclusively involves drilling long-reach horizontal laterals from a single pad, which puts extreme stress on the rig and equipment. Technology advancements took the industry from 2-mi laterals in 2018 to 4-mi laterals by 2024, and new well designs continue to push the limits of the equipment, with U-turn (or horseshoe) wells introducing a 180^o turn that creates enormous friction and localized stress. Technical challenges are compounded, as wells get longer and more complex.  

Because drilling horizontally for thousands of feet creates immense friction, managing drill string torque and drag is fundamental to executing an effective drilling program. To contend with the challenges introduced by friction, a rig must have sufficient power, torque, and reliable advanced downhole equipment to rotate the drill pipe without getting stuck, twisting-off or losing control of the well path.   

The relentless pursuit of better performance has resulted in greater demand for high-specification equipment that enables a rig to manage heavy loads while executing precise and efficient drilling performance over multiple, complex deep, long wells. Recently introduced technologies are delivering results, but true automation can only deliver optimal performance, if it is seamlessly integrated in the rig design.  

RAISING THE BAR FOR PERFORMANCE 

In some instances, operators are working directly with drilling contractors to improve rig capacity, so a standard rig can deliver the required cutting-edge performance. In fact, some of the best solutions have come from collaborative discussions that brought operators, service providers, and drilling contractors together to address persistent operational challenges.  

One such collaboration between Nabors Industries and Caturus Energy LLC led to a rig designed specifically for the operator’s drilling program in the South Texas Eagle Ford and Austin Chalk formations. The goal of the advanced rig design was to enable longer and faster drilling that meets the needs for this particular drilling program—where the operator is drilling to 14,000 ft, vertical depth, and laterals that are four miles long — and has the flexibility to be reconfigured for deployment in other environments.   

Fig. 1. The advanced capability of the new rig improves on the design specifications of the original unit, enabling drilling efficiencies that deliver superior performance and better project economics in much more challenging environments.

The operator wanted a rig designed with advanced capabilities that would shave off two days from the time historically required to drill a well, delivering a savings of about $200,000 per well. In simple terms, that meant that if Caturus executed a 25-well program over 12 months, the $5 million in savings equated to a “free well” at the end of the year.   

The companies recognized the need to incorporate multiple capabilities to allow the rig to achieve consistent performance in exacting conditions and designed the PACE-X Ultra^™ rig from a design introduced by Nabors more than a decade ago, Fig. 1. It is based on modularity and allows upgrades to be carried out in the field. With this approach, replacement equipment is readied in the yard, and installation is carried out on site over the course of a slightly longer-than-average rig move. The ability to upgrade setback capacity, mud pumps, engines, and high-pressure piping in the field instead of requiring a rig to return to the yard while upgrades are being made dramatically reduce rig flat time. 

The PACE-X Ultra^™ rig design has been upgraded, so that the rig floor can accommodate 35,000 ft of 5 7/8-in drill pipe, considerably more than a standard rig, and the design enables the rig to rack and walk between wells with 1 million-lb setback. The high-torque top drive can push up to 65,000 ft lb of drilling torque to enable longer laterals, and an upgraded mud system that incorporates three 2,000-hp mud pumps and a 10,000-psi mud circulating system allows more gallons/minute throughput at high pressure via piping that has been upgraded for high flowrate and fewer losses. To provide adequate power for this high-end equipment, the engines had to be upgraded to deliver the necessary horsepower to run this equipment. That meant replacing a standard 4-MW engine package, with a 6-MW engine package.  

IMPROVING ECONOMICS AND SAFETY 

Upgrading the rig to include Cat^® Dynamic Gas Blending™ (DGB) Gen 2 engines delivers both performance and economic gains. DGB engines, which operate on a mixture of diesel fuel and natural gas, save money by introducing gas into the energy mix and displacing diesel, which is more expensive. The DGB Gen 2 engines on the PACE-X Ultra™ X33 rig can run on a fuel mix that is 70% natural gas on average.   

Another advantage of employing these engines is that they are controlled by the Cat^® smart engine management system (EMS), which continuously monitors power demand fluctuations and automatically starts and stops the engines to provide the appropriate power level. By optimally loading the engines, the system ensures the active engines operate at a higher, more efficient load (80% to 90% of capacity) instead of having more engines running at a lighter, less efficient load. Because the smart EMS operates engines more efficiently), it not only reduces fuel consumption, but also lowers maintenance costs by significantly decreasing the total engine run time. 

Fig. 2. A unique rig design allows the unit to be configured for specific field conditions simply by replacing or adding components. (Photo courtesy of Nabors Industries).

Tying in rig floor automation improves both efficiency and safety, allowing high-risk tasks to be performed consistently and removing personnel from the most hazardous work areas. Hands-free pipe handling is fast and more precise and eliminates worker exposure to crush and pinch point injuries. Derrick automation allows pipe to be moved to and from the racking system without the need for worker intervention.  

DELIVERING VALUE WITH MODULARITY 

What makes this rig design unique is that it can be configured for specific field conditions simply by replacing or adding components, Fig. 2. With this “a la carte” approach, rigs can be configured with a range of capabilities that can significantly improve performance.  

For example, employing RigCLOUD^®, an open platform that increases performance by converting drilling data into drilling guidance, streamlines workflows and optimizes rig performance. And incorporating the equipment-agnostic SmartROS^® rig operating system allows the best workflows to be duplicated to enable consistency and increase effectiveness via an intelligent rig operating system that makes it possible to digitize and automate drilling processes.  

Another option is to add RZR Lite rig automation, which employs computer vision, a field of AI that enables computers to interpret, analyze and understand visual information. This capability removes the challenges of working in extreme light conditions, inclement weather conditions, and in environments with mud-covered pipe, to improve visibility into operations and decrease overall connection time. Automated tubular running services are another add-on option for handling tubulars to ensure efficiency and reliability in every part of the well. 

When well control is a concern, particularly in high-pressure environments, integrating a standpipe bleed-off system that works seamlessly with the rig operating system improves valve control and streamlines drilling connection. And in managed pressure drilling operations, an advanced drilling technique can be added to precisely manage the balance between wellbore pressure and formation pressure to mitigate drilling challenges and ensure control throughout the drilling process.  

PERFORMANCE PROVES VALUE  

Nabors put the rig to the test in the Eagle Ford shale on a drilling program for Caturus.   

When discussions began about designing an ultra-high-spec rig, the expectation was that it would be deployed in a region with more technically challenging drilling programs that stood to gain the most from efficiency improvements. Caturus, however, saw a different opportunity. Confident that the new technology could elevate output even in already strong-performing areas, the company chose to deploy the rig in one of its Eagle Ford drilling programs to test its true efficiency potential.   

For the initial drilling program, Nabors installed the required equipment in the yard and tested it before moving the PACE-X Ultra™ X33 rig to the site, where installation followed the standard process and protocols. This approach was taken for the first prototype to thoroughly test and proactively work through any kinks to enable a seamless performance when drilling began. Future upgrades and installations are likely to be performed on site rather than in the yard.   

Fig. 3. The PACE-X Ultra™ X33 established a new benchmark for performance in Webb County, reaching TD at 30,258 ft, and set a new bottomhole assembly footage record for Caturus at 20,387 ft. (Photo courtesy of Caturus)

Caturus wanted the rig to drill some of its most challenging high-pressure/high-temperature wells, reaching 14,000-ft vertical depths and laterals as long as four miles. The objectives of this program were to improve key performance indicators, improve safety and reduce the footprint of operations to help the company meet its goal to grow net zero production to 1 Bcfed by 2029.  

In executing this program, the rig established a new benchmark for performance, reaching TD at 30,258 ft, a new depth record for Webb County, Fig. 3. This achievement was among multiple milestones realized on this drilling program. The rig set a new bottomhole assembly footage record for Caturus at 20,387 ft and reached a TD of 2,570 ft per day from spud in 11.77 days. On the first pad, the rig delivered 25% improvement over Eagle Ford wells YTD, drilling 1,619 ft/day vs the previous rate of 1,305 ft/day. On the intermediate section of the well, the rig demonstrated best-in-class performance, with a 23% ROP improvement over the prior record. 

In general terms, the performance of the PACE-X Ultra™ X33 in the Eagle Ford showed that the ability to configure a rig for specific conditions and drilling objectives can produce significant drilling efficiencies. For Caturus, this project proved the value of Nabors’ advanced rig to deliver faster, more efficient wells, and demonstrated the potential for improving production across the company’s 200,000 Tier 1 net acres across Texas.   

Modularity and innovation have enormous capacity to change the face of onshore drilling. In the end, however, it is important to bear in mind that the critical advances that move drilling to the next level are not determined solely by new capabilities. Technology is undeniably foundational, but experienced people and established processes were essential to the execution of Caturus’ Eagle Ford drilling program and will be integral to future drilling advances.  

PAVING THE WAY TO THE FUTURE 

As drilling environments become more complex and demanding, the industry will continue to change and adapt to meet speed and efficiency requirements. The next iterative improvements will likely be better bits and motors and rotary steerable systems that can handle the friction, heat and pressure that will characterize new drilling environments. But as each inefficiency is addressed, the technology that resolves the challenge invariably introduces a new technical limit.   

When bit performance is restricting the rate of penetration (ROP), a new bit design that improves ROP could function so well that the mud pump is not able to circulate the cuttings out of the hole fast enough. So, the limiting factor is no longer bit performance but a pump that cannot return cuttings to the surface. The continuing need to address the new limiting factor is the driver for ongoing innovation.  

 As technologically advanced as the industry is today, it is possible that five years from now, the cutting-edge equipment that is being introduced today will be considered antiquated, and new rig designs will be demonstrating how automation, more horsepower, and higher-pressure performance can deliver results that are inconceivable today. 

BRETT SCHELLENBERG is the vice president of Global Sales for Nabors. His expertise in the oil and gas sector spans nearly two decades, beginning with hands-on experience as a floor hand. He has served in various capacities at Nabors, including Digital Technologies, Automation, and Operational Management. Brett is a proud graduate of Texas Tech University.