Sustainability: Meeting new drilling demands with smarter power management

LANCE ELLINGTON, HELGE KJEVIK and ALEKSANDER TAANEVIG, NOV 

In today’s climate of rising fuel prices and stricter environmental regulations, drilling operations are tasked with maximizing rig efficiencies while minimizing greenhouse gas emissions. Achieving these goals drives a need to optimize power generation through smarter, more efficient operation of the combustion engines that make up a drilling operation’s grid.   

Conventional methods to curb emissions from combustion engines often limit the power capability of the rig’s generators and increase the risk of power outages, which can lead to costly downtime and reduced drilling efficiency. To mitigate these risks and maintain peak performance on the rig, the industry requires drilling rig controls and processes that optimize power usage for the various pieces of rig machinery while ensuring that the rig’s power grid meets its emission targets.  

This article reviews some recent power control and optimization solutions that NOV has developed to help drillers meet their dual objectives of peak drilling performance and lower carbon emissions.  

OPTIMIZING ENERGY USAGE WITH INTEGRATED CONTROL 

To minimize the risk of a power disruption that impacts rig performance and lowers overall drilling efficiency, rig control systems must incorporate fully integrated power management, engine management and real-time measurement of drilling tool power consumption.   

Power management is a broad term that defines the necessary steps to prevent engine overloads while ensuring that the various rig operations receive adequate power, particularly during times of peak demand. An effective power management system must have the capability to perform power limiting. 

Effective engine management comes from software and hardware solutions, such as load-dependent stop/start, which automatically adds or removes power-generating units from the system, depending on power requirements at any given time.  

Drilling tool power consumption systems are an often overlooked, but critical, class of solutions that focuses on achieving acceptable drilling tool performance while limiting any actions that lead to a spike in carbon emissions. Having the ability to limit kilowatt-scale ramp rates applied to the engines and smoothing out peak energy spikes to the power grid is crucial. 

While many systems are available to ensure effective power management and control the power consumption of each tool, they must be effectively integrated to maximize drilling performance with minimal emissions. NOV designed the Maestro management system to deliver on these goals.  

As an add-on product for NOV drilling control systems, the Maestro system helps reduce fuel consumption across the rig while maintaining safe drilling operations. The configurable system monitors drilling equipment while calculating and determining the appropriate, safe levels of required power generation. Unlike reactionary systems, it functions in real time and in tandem with rig operations. With built-in overrides, the system makes full power available when rig operations demand it.  

Maestro also affords greater power plant control with load shed monitoring that measures the difference between capacity and the loads on each generator. The drilling operator uses this information in combination with preset or user-adjustable set points to take an engine generator set offline or bring an additional set online, as power needs dictate.  

Its load shed profiling also allows the power system to be configured to operate under a number of preset, pre-approved, and optimized scenarios. The system will shed power on individual tools, based on the preconfigured arrangements for the drawworks, top drive and mud pumps. A Drilling Profile will prioritize power to the top drive and mud pumps over the drawworks, but it will ensure that the drawworks does not lose control of the load. A Tripping Profile will give priority to the drawworks over the mud pumps and top drive.  

Maestro helps fully automate engine controls with upgrades that completely avoid the need to replace existing control electronics. This system’s automation package upgrades existing drilling system controls to allow the operator to manage and monitor a rig’s drilling applications and power efficiency in real time. Moreover, this automation upgrade can be completed in just a few days and in tandem with a rig move to minimize downtime. Because the system retains up to 90% of the original control components, upgrade costs are minimized.  

CAPTURING LOST ENERGY TO REDUCE EMISSIONS 

A drill floor contains several large pieces of machinery that require significant power. The main power consumer is the drawworks, which can pull approximately 1.2 MW per motor installed. During hoisting operations, the drawworks demands peak power within just a few seconds, which puts significant stress on the generators.  

Multiple generators are often used to simultaneously provide more power to the drawworks and other equipment on the drilling rig during brief, peak demand periods. These situations, which are quite common during drilling, require the generators to operate at different speeds for various periods of time, leading to uneven electric load generation, increased fuel consumption and higher carbon emissions. 

When a load is lowered, braking resistors on the drawworks engage to slow down the motion, generating energy that is typically burned off as heat. NOV created the PowerBlade kinetic energy recovery system to recover this braking energy and ease the power demands and CO₂ emissions of a rig’s generator systems, Fig. 1. The system harnesses energy from the braking resistors and stores it in a flywheel, a battery or a combination of the two. This stored reserve of energy is then dynamically returned to the rig’s energy grid to shave off the peak power demand during the next hoisting cycle.  

Fig. 1. The PowerBlade kinetic energy recovery system installed at the NOV test site.

The energy recovery system’s electric load-leveling capabilities replace a fluctuating power current with a stable power supply that reduces spinning reserves while maintaining sufficient power for the generators. In the event of a power loss, rig machinery has access to a stable reserve of backup power without incurring downtime or drilling delays.  

By enabling peak shaving, the system helps improve the energy efficiency of the rig’s grid. Fewer generators are required to supply power to the drawworks and other rig equipment, which helps reduce fuel consumption by up to 20% or more. The generators also operate at an optimal rpm level, which eases wear and tear, lowers maintenance costs, minimizes the risk of a generator tripping off and reduces generator cycle duty. 

The energy recovery system helps reduce CO₂ and NO_x emissions during drilling by enabling more efficient energy usage. It also adds greater flexibility to the grid’s power distribution and load profile, which helps improve equipment performance and operational speed. Simulations show that the system enables up to 20% faster tripping speeds from the drawworks.  

This system also increases safety by creating redundancy within the power grid. In addition, it helps ensure safe and even power distribution to the power splits/buses. 

IMPROVING EFFICIENCIES WITH OPTIMIZED RIG HYDRAULICS  

Today’s rig fleet is becoming increasingly automated to optimize energy usage, improve efficiencies, lower emissions and improve safety by removing more personnel from potentially unsafe operations on the rig floor.  

To capture the full speed and efficiency benefits of automated operations on the drilling rig, several machines must operate simultaneously on the rig floor. Many of these machines are hydraulically driven by a large ringline hydraulic power unit (HPU) that must accommodate rapidly changing flow requirements on the drill floor. The number of running pumps on the HPU must match the highest theoretical flow requirement, even when a peak lasts only a few seconds.  

Fig. 2. EcoBooster stabilizes ringline pressure and enables peak shaving on the HPU.

The HPU’s significant distance—50 m (164 ft) or more—away from the nearest consumer complicates meeting this requirement and leads to pressure losses. In situations of significant pressure losses (15–25 bar), machines with high flow requirements can experience a slowdown in their movement and operation. In some cases, this slowdown results in a complete stoppage of automated operations. 

With the introduction of automated pipe-handling systems, which are particularly sensitive to pressure fluctuations, it’s critical to maintain a steady, high-pressure flow and keep the system running smoothly.  

NOV’s EcoBooster ringline pressure boost system is designed to maintain high, steady pressure in all machines connected to the HPU, regardless of the flow requirements at any given moment. The hydraulic energy storage system consists of a skid-mounted bank of compact accumulators and a booster pump, Fig. 2. When ringline flow consumption is low, the booster pump charges the accumulator bank to a pressure of 240 bar, roughly 30 bar higher than the rig’s total pressure requirements at baseline conditions.  

When a flow peak event that exceeds the ringline HPU’s capacity occurs, the charged accumulators deliver the extra hydraulic energy to match the flow demands of the pump requiring it. As a result, the system helps stabilize ringline pressure (Fig. 3) to enable peak shaving on the HPU while enhancing pump performance and reducing the number of active pumps running in the HPU by more than 50%.  

Fig. 3. Log data from a tripping operation show that activating the ringline pressure boost system helped smooth out pressure fluctuations while increasing system pressure.

 This reduction in active pumps translates to reduced fuel consumption, carbon emissions, maintenance, and costs. Operating half the number of pumps on a typical drilling rig saves an estimated 800-1,000 MW of power and 400,000 liters of diesel fuel per year, as well as 1,300 tons of CO₂ and 2 tons of NO_x emissions. 

MINIMIZING GENERATORS AND EMISSIONS IN THE NORTH SEA 

(Editor’s note: The data in this section are from a business case in 2022 and may be superseded by current results.)

A drilling contractor installed the PowerBlade energy recovery system on a semisubmersible operating in the Norweigian North Sea to ease the load requirements on the rig’s generators. The system’s combination of flywheel and battery storage was installed on the rig deck and interfaced with the rig’s main DC drilling bus. Maestro also was installed to constantly balance the power needs of the rig equipment with the stored and generated power. The power management software helped effectively control the energy flows, keeping the power demand on the generators as low as possible. 

PowerBlade effectively captured up to 600 kWh of electrical energy generated from the drawworks braking power and provided up to 6 MW (3 MW from the battery and 3 MW from the flywheel) of peak-shaving power to the drawworks. As a result, the rig’s generators did not have to work as hard to provide the short burst of peak power to the drawworks. 

The combination of the energy recovery system and the DC/DC grid system reduced the number of diesel generators onboard, improving generator load utilization rates while lowering fuel consumption per kWh of electricity generated. It also reduced maintenance requirements and minimized carbon emissions during drilling operations.  

This combined solution allowed the rig to operate on just one generator for a significant period, even during drilling and tripping operations. The energy recovery system’s 6-MW peak-shaving capabilities translated to more stable power demand from the drilling equipment onto the generators. Generator sizing became more predictable, which gave the rig crew greater confidence to run fewer generators at a higher load level, reducing the rig’s fuel consumption by 25% to 30% in the process. 

CONCLUSION 

As the drilling industry strives to balance higher efficiencies with lower emissions, smarter power management systems like the ones presented above offer a viable, sustainable solution. Moreover, as the drilling landscape keeps changing and new challenges arise, operators, contractors and equipment manufacturers will have to work together to develop new technologies for the future of drilling. 

About the authors

LANCE ELLINGTON joined National Oilwell Ross Hill in 1997 after serving six years as a Fire Control technician in the U.S. Navy. He has held various roles at NOV, from field service to engineering to operations manager, and now serves as Product Line Manager, covering Power Systems, Amphion Controls and Red Zone Management.   

HELGE KJEVIK is the Global Product Line Manager for Motion Compensation and Hydraulic Power Units at NOV. He joined Hydralift in 1996, developing Heave Compensation for cranes and rigs. He joined NOV through the acquisition of Hydralift. Mr. Kjevik holds a degree in mechanical engineering from the University of Agder, Norway. 

ALEKSANDER TAANEVIG is NOV’s Product Line Manager for offshore pipe-handling equipment and PowerBlade, managing a global portfolio of machines manufactured, maintained and sold by NOV. He joined NOV’s Field Engineering group in 2018, working with aftermarket upgrades and modifications globally as a Sales Engineer. He joined NOV’s Product Line Group in January 2024 and holds a BSc in Mechatronics Engineering from the University of Agder in Grimstad, Norway.