Decarbonizing drilling operations using more efficient electrical utility power

INTRODUCTION

Conventional oil and gas drilling rigs need electricity to operate equipment from top drives and drawworks to control systems. The industry today relies heavily on diesel generators for rig site power supply, in great part because of generator portability. Although powering a rig using electrical power from the utility grid has been possible for many years, this solution has not been implemented widely. This is due to the lack of reliable electric infrastructure; operating costs; the complicated logistics of moving substations from drilling pad to drilling pad; and the complexity of connecting rigs to a power source in a way that provides consistent, reliable power.  

Historically, highline electrical power was employed to minimize noise pollution in urban drilling areas, but increasing environmental consciousness, driven by initiatives like the Paris Climate Accords and the growing public desire to reduce emissions and improve air quality, has helped electrification of drilling operations gain traction. The environmental impact of diesel generators—marked by high operating costs and significant CO2 emissions—can be mitigated by transitioning to highline electrical power, which offers a more cost-effective and environmentally friendly approach to rig electrification; The integration of renewable energy sources further enhances the environmental benefits of electrification.  

The recent shift to using utility grid power for drilling sites reflects not only the objective of economically improving drilling operations but aligns with environmental and decarbonization goals in the pursuit of net-zero operations. 

A drilling rig typically requires anywhere from 6 MWh to 50 MWh of energy per day, with an average rig using approximately 20 MWh per day. Using diesel to meet that energy demand emits a considerable amount of CO2e, which normally averages 20 metric tonnes of CO₂e per day on location. The emissions intensity when powering a rig with diesel fuel is roughly 1.0 metric tonnes of CO₂e/MWh. Powering the same rig from the grid, with its ability to utilize larger and more efficient generators and clean sources of energy, emits roughly 0.39 metric tonnes of CO₂e/MWh, which is slightly less than half the emissions intensity of using diesel-powered generators.  

The introduction of a simple system that connects a rig to the utility grid has changed the status quo, and now, there is increasing interest in highline power on drilling sites. A substation transformer is employed to act as a safe and reliable “power conductor” between the grid and the rig. It steps down the incoming highline voltage to the required rig voltage and frequency, serving as an interface between the utility grid and the rig’s powerhouse. 

Rig electrification is agnostic to the power being received. Switching to line power is simple and straightforward, which means more rigs can be connected easily to the grid, as infrastructure changes and grids become more efficient. If a grid is particularly efficient—like the ERCOT grid in Texas, which primarily relies on wind power and natural gas—the net CO2e reduction can be dramatic. But, even grids with a higher emissions intensity deliver significant emissions reduction over power generation from diesel-fueled generators.  

A good illustration is a comparison between drilling operations in North Dakota and Texas. In North Dakota, power generation is more dependent on coal as a share of its energy production. According to the 2022 NEI State Electricity Fuel Shares, 57% of power generation in North Dakota uses coal vs 18% in Texas. Emissions intensity on a North Dakota rig tied to the utility grid is higher than that of an electrified rig working in Texas, but it is still notably lower than the intensity of an average drilling rig powered by a diesel generator, which is approximately 1.0 metric tonnes of CO2e/MWh. 

Regardless of the fuel used to generate electricity, electrification significantly reduces the carbon footprint of drilling operations. In regions where an abundance of field gas surpasses local consumption, excess gas is being used to generate electricity. As a cleaner-burning fossil fuel, gas can be used to produce electricity more cleanly than coal or other hydrocarbons. Using produced gas for power has the added benefit of eliminating the need for flaring. 

INTEGRATION AND OPERATIONS

Successful implementation of highline power on rig sites requires a thorough engineering evaluation of grid capacity, power output, incoming frequency, voltage output and power requirements. Key components, such as transformers, harmonic filters, switchgear, plug panels, cable reels, and metering systems, must be assessed well in advance for proper integration. But the key in delivering and employing a fit-for-purpose solution relies on the portability, robustness and safety of the interface system between the local grid and the rig, Fig. 1.  

Fig. 1. Operational units, showing the connection between the highline power module (left) and the utility grid (right).

Ensuring secure and safe energy pathways, medium-voltage connections and visual indicators is critical to creating an optimal design. Appropriate operations and maintenance procedures are necessary to ensure proper installation and safe, reliable operation in the field. 

Technical overview. examining the 32-ft by 10-ft portable skid for U.S. operations provides valuable insight into highline power technology. The transformer, a central component, steps down the source voltage to match the rig’s voltage requirements. The module’s primary coil (with ten voltage settings) ensures adaptability to different grid and operational voltages. Harmonic filters, switchgear, plug panels, cable reels, and metering systems play pivotal roles in maintaining stable power supply and facilitating the connection between the rig and the grid.  

To expand the reach of the technology to international markets, where gird frequencies are lower than those in the United States, a new unit was designed in 2021 and manufactured in 2022. It takes system development a step further and allows connection to drilling rigs operating on 50-Hz highline power grids. This new unit, built for a project in Argentina, uses the same equipment as a rig in the U.S., with the addition of a VFD component to ramp up the incoming frequency to meet the rig’s 60-Hz requirements.  

Transformer details (24.9kv U.S. and 33kV International). The highline power module unit’s transformer, a key component, steps down the source voltage to the required voltage of the rig with a standard configuration of a 24.9-kV primary and 600-V secondary transformer. This configuration suits most U.S. operations, and specifications can be adapted for different regions with varying voltage requirements. The international version has a standard configuration of 33-kV primary and 600-V secondary. 

Harmonic filter. The integrated active harmonic filter in the highline power unit addresses varying loads and offsets harmonics caused by rig operations. This helps to ensure the requirements of IEEE 519-2022 Standard for Harmonic Control in Electric Power Systems are met as well as the standards of the utility company.  

Switchgear. Rig electrification incorporates three transfer switches for a seamless transition between utility power and generator power, ensuring continuous power supply with interlocked switches to prevent simultaneous energization from both sources.  

Plug panel & integration. The plug panel facilitates the connections among the transformer, powerhouse, and generator sets, supporting three-phase power via a customized cable kit.  

Cable reel. A cable reel with 1,000 ft of medium-voltage, 3-conductor cable simplifies rig-up, providing flexibility in connecting to the utility grid while accommodating rig moves.  

Frequency conversion. While utilizing the 50-Hz highline power, the proprietary built-in frequency conversion system enables operation of all non-VFD equipment to be powered with the correct frequency. 

Voltage regulation. Using optional voltage regulation equipment, it is possible to regulate the incoming highline power to eliminate inconsistent voltage outputs. 

Data collection and monitoring. The highline power module is equipped with a power meter that measures the electric usage of the rig, as well as other useful power quality data. Figure 2 shows a schematic that illustrates how the highline power module connects to the utility grid. Engineers designed and tested a means to collect these data from the meter remotely to allow operators to understand their electricity usage. This feature is in the process of being implemented in the field. 

Fig. 2. Schematic showing the connection between the highline power module and the utility grid.

Because some international power grids have different specifications from those in the United States, engineers developed a way to adapt the existing module to deliver the same functionality for grids supplying different levels of voltage, Table 1.  

Environmental benefits. Highline power and highline power technology offer a substantial reduction in on-site emissions compared to traditional diesel-electric power generation, making a compelling case for achieving zero rig-site emissions.  

• Zero rig site emissions for power generation. An analysis comparing daily fuel consumption and emissions from diesel-powered rigs to highline power-connected rigs in West Texas highlights substantial emissions savings and the elimination of on-site CO2 emissions. The adoption of highline power contributes to cleaner and safer work environments, enabling operations in markets with emissions restrictions. 
• Area technical review. By leveraging the available power demand data obtained from the rig, it becomes possible to compute the CO2 emissions associated with diesel power generation activities. These emissions data can then be applied to estimate the CO2 emissions generated by highline grid power in the same operations. Figure 3 illustrates the percentage reduction in CO2 emissions achievable through the adoption of highline power. This breakdown specifically focuses on two regions: North America and Latin America. 

Fig. 3. Percentage decrease in CO2 emissions generated, using highline power instead of Caterpillar generators on drilling rigs working in different regions of North America and Latin America.

U.S. FIELD VALIDATION AND ONSITE IMPLEMENTATION

Throughout the initial phases of implementation and the final development of the highline power module, the engineering team conducted thorough testing and validation during manufacturing and field deployment to ensure seamless integration with rig systems. As part of this approach, engineers devised a comprehensive multi-step testing process to assess the effectiveness of the power transformer module, ensuring its simplicity and reliability. 

At a Magnolia, Texas, manufacturing facility, prototypes were connected to a voltage source, with the unit's performance closely monitored and measured according to standard quality control (QC) processes and procedures. Following testing under various operating conditions, the unit was shipped to the rig site for installation on a Nabors drilling rig. 

Designed with compatibility in mind for alternating current (AC) rigs, the inaugural installation of the highline power module took place on a Nabors rig in March 2022. The unit’s successful performance laid the groundwork for subsequent integrations by other drilling contractors, commencing in August 2022.  

Field implementations have generated compelling data that illustrate the impact of electrification on reducing fuel consumption, emissions, and operating costs.  

A noteworthy installation was carried out on a Nabors rig in West Texas that was consuming 20 MWh/day to 25 MWh/day of electricity. A typical configuration for rigs relying exclusively on onsite generators is to fit the rig with four diesel generators, because operations often require, on average, 3.5 generators online over a well cycle. 

Using the equation 22,500 kWh × 0.063 gals of diesel fuel/kWh + 3.5 generators using 7 gals/hr of diesel, running 24 hr/day, the estimated average daily fuel consumption for a rig is approximately 2,005 gals, resulting in 20.5 metric tonnes of CO2e emitted daily (2,005 gals of diesel fuel × 0.01021 metric tonnes of CO₂e/gal diesel). 

The average daily CO₂e produced, using a highline power unit, depends on the efficiency of the utility grid. Taking the West Texas rig as an example, where the grid is 53% more efficient at producing energy than diesel power generators (comparing CAT 3512C generator sets to the Texas ERCOT electrical grid), this technology can deliver an average emissions savings of roughly 10.3 metric tonnes of CO₂e and eliminate the use of approximately 2,005 gals/day of diesel. 

ARGENTINA'S FIRST RIG ELECTRIFICATION DEVELOPMENT 

Rig electrification has established a foothold in the U.S., and successful installations of highline power systems have led to interest in other areas, including Latin America, particularly Argentina. There, energy companies are working to improve the carbon footprint of operations. 

Argentina is a leader in greenhouse gas (GHG) emissions reduction in Latin America. The only country in the region that is a member of the G20, Argentina is investing in renewable energy and has set ambitious goals, launching the Plan de Desarrollo Productivo Verde (DPE), a roadmap for green industrial development, in July 2021 and setting 2050 as a net-zero emissions goal. According to the 2022 Argentina Climate Transparency Report, decarbonization is underway, and progress has been made to incorporate more renewables in the electricity generation plan.  

This effort is already achieving positive results. Between 2016 and 2021, Argentina’s emissions intensity dropped 24%, compared with the 8% average reduction for the G20 countries. In 2021, the country produced 64% of its electricity from fossil fuels, but that percentage is slowly dropping with the incorporation of cleaner sources, including solar, wind, biomass and small hydro (under 50 MW). For each kilowatt hour of electricity, the country emits 288 g of CO₂ (Climate Transparency – Argentina, 2022). 

Argentinean energy company Vista is changing its approach to exploration activities, making decarbonization a top priority in alignment with the country’s carbon reduction objectives. In 2012, the company published its own goal of being net zero by 2026, even as it accelerates development and increases production. 

For several years, the company has explored innovative approaches to electricity generation and identified the use of compressed gas combustion as a promising solution. This method involves harnessing the energy stored in compressed gas to drive turbines and produce electricity. In Argentina, where natural gas reserves are abundant, leveraging compressed gas combustion provides an efficient and cleaner alternative to traditional fossil fuel-based power generation. 

This technology capitalizes on Argentina’s abundant natural gas reserves, offering a cleaner and more efficient alternative to using traditional fuels, helping to diversify the energy mix as it dovetails with global efforts to transition towards more sustainable and environmentally friendly energy sources. Implementing CGC diversifies the energy mix, aligning with global efforts to curb fossil fuel dependence and increase reliance on renewable sources, Fig. 4. Focusing on electrification as an enabler, the company is using gas compression for electricity generation and is laying plans to purchase energy from renewable sources.  

Fig. 4. Vista projections illustrate how incorporating electricity generated from renewable sources will reduce Scope 1 and Scope 2 emissions.

Vista considered multiple options for developing its Bajada del Palo Oeste (BPO) unconventional field in 2019 to meet its execution goals of reducing noise and lowering carbon emissions without compromising project economics. In pursuit of its net-zero objective, Vista made the decision to use high-line power on both its BPO and Aguada Federal (AF) developments as part of its five-year plan. In implementing this solution, the company aimed to increase the reliability of the electrical systems on its rigs to reduce production downtime. 

One of the considerations for electrifying the BPO and AF fields was grid infrastructure. The grid would need to be extended, to allow BPO to connect to the Argentine Interconnection System (SADI). The company also would need to sign a Power Purchase Agreement with SADI to formalize the agreement. This process got underway in February 2023. 

Vista spearheaded expansion of the local grid to support drilling operations as the first operator in the country to tap into the electric utility grid. This investment facilitates the company’s sustainability initiatives in the region. At the same time, it makes it easier for businesses and communities to transition away from fossil fuels. By investing in the local grid, Vista is not only taking a holistic approach to transforming its own operations but is enabling positive change within the communities where it operates.  

In Phase 1 of the project, Vista established the interconnection between SADI and the BPO electrical infrastructure. This included expanding the Loma Campana transformer by replacing the existing 15-MVA transformer with a new 45-MVA transformer to allow for greater capacity on the line.  

In Phase 2, Vista engaged with Canrig to develop an interface unit that can be used to connect the local grid and the rig. Phase 3, field installation and commissioning, was scheduled for completion in second-quarter 2024.  

LOOKING AHEAD: A PROMISING OUTLOOK FOR EMISSIONS REDUCTION

The successful installations of the highline power transformer module in diverse U.S. operating environments underscore the efficacy of leveraging utility grid power to decarbonize drilling operations. Recognized as a proven, practical, cost-effective, and reliable energy source, grid power holds the potential to revolutionize land drilling practices on a global scale.

One U.S. based energy company, Hess, has been utilizing this proprietary highline power transformer module on four of its rigs working in the Bakken Shale. Hess estimates that employing this solution on just these four units will reduce the company’s Scope 1 GHG emissions from its Bakken drilling operations by 50% over the course of five years (Pallanich, 2023). 

While the United States currently dominates the rig electrification market, other geographies and pivotal oil- and gas-producing countries and regions are swiftly following suit. Latin America and the Middle East are actively considering the integration of electrification into their resource development strategies.

To enable installations in regions where utility grids operate at different frequencies, engineers already have devised a tailored solution for Argentina that addresses the need to convert the native utility grid frequency from 50 Hz to the more commonly used 60 Hz used on drilling rigs. Using a frequency converter module in the existing highline power module enables the conversion of the standard utility power from a 50 Hz frequency to the 60 Hz frequency essential for rig operations. 

The fact that oil and gas operations contribute to 15% of global energy-related emissions has prompted leading energy companies worldwide to earnestly seek solutions for change (OECD, 2023). To progress toward net-zero operations, the industry must explore viable alternatives to traditional hydrocarbon-based fuel consumption.

The electrification of drilling rigs emerges as a key driver in expediting this transformative journey. As global markets advance their electric grids, the potential for rig electrification expands, presenting opportunities for energy companies to not only meet but exceed their operational sustainability goals. 

Notes:

†All emissions comparisons to CAT 3512 C Diesel-Electric Generators are done with electrical power production at 40% engine load (average engine load for typical drilling operations) unless otherwise noted. Grid emissions factors utilized EPA’s Electrical Power Sector Basics or EIA’s How much Carbon Dioxide is Produced Per kilowatthour for U.S. 

ACKNOWLEDGMENT 

This article is based on paper 24OPES-P-788-SPE, presented at the SPE Conference at Oman Petroleum & Energy Show, April 22–24, 2024.  

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