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Review

O&G, Geothermal Systems, and Natural Hydrogen Well Drilling: Market Analysis and Review

by
Andreas Nascimento
1,2,3,*,
Diunay Zuliani Mantegazini
1,*,
Mauro Hugo Mathias
1,
Matthias Reich
3 and
Julian David Hunt
4
1
School of Engineering and Sciences, São Paulo State University (UNESP), Guaratinguetá 12516-410, Brazil
2
Institute of Mechanical Engineering, Federal University of Itajubá (UNIFEI), Itajubá 37500-903, Brazil
3
Institute of Drilling Engineering and Fluid Mining, Technische Universität Bergakademie Freiberg, 09599 Freiberg, Germany
4
Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
*
Authors to whom correspondence should be addressed.
Energies 2025, 18(7), 1608; https://doi.org/10.3390/en18071608
Submission received: 20 January 2025 / Revised: 9 February 2025 / Accepted: 11 February 2025 / Published: 24 March 2025
(This article belongs to the Section H: Geo-Energy)
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Abstract

:
Developing clean and renewable energy instead of the ones related to hydrocarbon resources has been known as one of the different ways to guarantee reduced greenhouse gas emissions. Geothermal systems and native hydrogen exploration could represent an opportunity to diversify the global energy matrix and lower carbon-related emissions. All of these natural energy sources require a well to be drilled for its access and/or extractions, similar to the petroleum industry. The main focuses of this technical–scientific contribution and research are (i) to evaluate the global energy matrix; (ii) to show the context over the years and future perspectives on geothermal systems and natural hydrogen exploration; and (iii) to present and analyze the importance of developing technologies on drilling process optimization aiming at accessing these natural energy resources. In 2022, the global energy matrix was composed mainly of nonrenewable sources such as oil, natural gas, and coal, where the combustion of fossil fuels produced approximately 37.15 billion tons of CO2 in the same year. In 2023, USD 1740 billion was invested globally in renewable energy to reduce CO2 emissions and combat greenhouse gas emissions. In this context, currently, about 353 geothermal power units are in operation worldwide with a capacity of 16,335 MW. In addition, globally, there are 35 geothermal power units under pre-construction (project phase), 93 already being constructed, and recently, 45 announced. Concerning hydrogen, the industry announced 680 large-scale project proposals, valued at USD 240 billion in direct investment by 2030. In Brazil, the energy company Petroleo Brasileiro SA (Petrobras, Rio de Janeiro, Brazil) will invest in the coming years nearly USD 4 million in research involving natural hydrogen generation, and since the exploration and access to natural energy resources (oil and gas, natural hydrogen, and geothermal systems, among others) are achieved through the drilling of wells, this document presents a technical–scientific contextualization of social interest.

1. Introduction

Reducing greenhouse gas emissions has been the common global goal in terms of energy strategies for years, gaining more importance recently [1]. Signed in 2015, the Paris Agreement has set a target, limiting the global mean temperature increase below 2 °C over the pre-industrial period and pursuing an effort to limit the temperature rise to 1.5 °C [2,3,4,5,6]. In addition, it aims to reach net zero greenhouse gas emissions in the second half of the 21st century [2,4]. To reach this goal, countries race to develop new technologies to secure the incorporation of renewable energy sources into the grid and enhance the adaptability of energy systems [7].
Developing clean and renewable energy, alongside a guarantee of less utilization of fossil fuels, is the main way to compile to the energy transition and mitigate climate change [1]. The International Energy Agency (IEA) has established a forecast for renewable energy sources, indicating it may represent approximately 40% of the worldwide electricity supply by 2030 [8,9]. The search for low-emission technologies and the requirements of complying with climate change needs has created the potential for geothermal and natural hydrogen energy as a considerably important supplying source
The drilling industry is essential to the exploration and production of several energy sources, such as oil and gas, geothermal energy, and natural hydrogen. The oil and gas sector remains the primary global energy source, driven by demand for fossil fuels and petrochemicals, although it faces challenges related to the energy transition. Geothermal energy is a clean and renewable energy source and can be used for different purposes, such as space heating, water heating, and electricity generation, among others [1]. It is a mature and commercially proven energy resource with considerable potential to become more competitive in the next few years, besides being a stable source, enabling uninterrupted electricity production independent of weather conditions [10,11]. Meanwhile, natural hydrogen is emerging as a promising alternative in the context of decarbonization, with in-progress research aiming to enable its commercial exploration [12]. In this scenario, advancements in drilling techniques are essential to optimize operational efficiency and reduce costs, making the exploration of these resources more viable and sustainable.
In oil and gas, geothermal, and natural hydrogen exploration/exploitation, it is necessary to have drilling wells connecting the surface to the subsurface/reservoir, i.e., a pathway to access the natural resources [1,13]. Rotary drilling is the predominant method employed for drilling in oil and gas fields worldwide [14]. The extraction of these natural resources (geothermal and natural hydrogen) faces challenges similar to those found in the oil and gas industry. One main issue is wellhead stability, as changes in temperature and pressure can compromise the integrity of the well structure. Additionally, geomechanical factors affect both hydrogen and oil drilling, with risks such as lost circulation, wellbore instability, and unwanted fractures that may compromise well integrity. Operational parameters and pressure control are also critical, since drilling fluid management is necessary to prevent formation collapse and avoid unexpected fluid influxes [15,16,17].
The rate of penetration (ROP) and mechanical specific energy (MSE) are key factors in measuring the efficiency of the drilling process [18,19,20]. Experimental results indicate that ROP and MSE are influenced by the physical characteristics of the rock, as well as drilling parameters. To overcome these challenges, pre-operational tests and multi-objective analyses must be performed. The pre-operational test is a practical procedure for measuring the relationship between the ROP and key drilling parameters, such as WOB and RPM, while multi-objective optimization searches for the ideal combination of high ROP and low MSE for a given lithology.
Due to the challenges presented, drilling activities have become one of the main and most expensive phases of energy resource exploration/exploitation [21]. The drilling operations are responsible for approximately 50% to 70% of the total expense of enhanced geothermal system (EGS) projects. The drilling operation alone, excluding casing and cementing phases, is responsible for 25% to 40% of the total drilling costs and over 40% of the total well construction time [22]. In this sense, the costs associated with the drilling and completion phases are often the decisive factors in determining if these energy resources are a technical and economically feasible energy source [23] when considering a wide and commercial scale.
In a general perspective, access and exploration to many energy-related natural resources, such as the ones emphasized in this paper, namely O&G, geothermal, and natural hydrogen, are drilling-dependent. In this context, the goals of this research are to evaluate the global energy matrix, highlighting the production and forecasts over the years and for the future, respectively, combining the relevance of the drilling engineering discipline.

2. Oil and Gas

Despite the progress over the years in terms of drilling methods, techniques, and technology, the process continues to be complex, challenging, and expensive. The parameters that affect the drilling process are divided in three categories as follows: (i) parameters related to machinery, equipment, and cutting tools; (ii) parameters related to the rock properties; and (iii) parameters related to the drilling activities itself, such as adjustable operational and technical parameters [21].
Currently, the focus of global O&G companies is exploring offshore deep and ultra-deep locations [24], mainly due to their potential, the continuous depletion of shallow resources, and continuous increase in global energy demands [25]. Offshore ultra-deep well drilling is a complex process which often involves challenges, high risk and costs, and in some unconventional locations, it reveals low rock-breaking efficiency (due to abrasiveness and high rock strength) and a low rate of penetration (ROP) [20,24,25,26,27].
The exploration and development of oil fields in deepwater and ultra-deepwater offshore regions have increased the risks associated with the drilling process [28]. One of the challenges facing pre-salt reservoirs is related to the creep in salt rocks, a phenomenon in which salt gradually deforms over time due to temperature fluctuations, viscosity, mechanical stresses, and microstructural properties [29]. During drilling, salt creep can lead to borehole closure and the drilling BHA becoming stuck, which significantly inflates the operational time and costs. In the same context, uncontrolled borehole enlargement caused by the dissolution of salt in non-saturated water-based drilling fluids can hinder casing installation and cementing [30]. Even though it is challenging, salt drilling has already been controlled by the industry so that know-how and technologies are already in place for such pre-salt operations. Still regarding this environment, carbonate rocks (pre-salt reservoir) are, to date, garnering a lot of attention given the high tendency of drilling fluid loss, a narrow mud window, low penetration speed (historically approximately from 0.5 to 8 m/h), and difficulties in maintaining a consistent drilling efficiency. In this context, MSE is extensively used to measure the effectiveness of the drilling process [20,31]. Mantegazini et al. (2024, 2025) [19,20] applied the MSE concept to analyze field datasets from a real pre-salt operation, where rooms for drilling efficiency improvements could be drawn from pre-operational drilling tests with a multi-objective focus.
In addition, there are costs related to the rent and operation of drilling platforms, drilling rigs, and/or drill ships. The daily rent of offshore drilling platforms in the South China Sea ranges from USD 294,000 to USD 515,000 depending on the platform’s characteristics [32], while the platform’s operating costs range from USD 300,000 (shallow water) to USD 500,000 per day (deep water) [24]. According to [33], the average cost to drill the pre-salt layers ranges from 641,985.00 to 1,374,755.00 [USD/day] depending on the type of the drilling platform in use and unexpected occurrences. It is estimated, in a general sense, that during the drilling operations, 48% of the time is spent effectively penetrating the rock (drilling the hole), 27% in round trips (e.g., drill bit replacement), and 25% for well measurements and formation evaluation (offset and not in real time) [14].
These facts show that exploring subsurface resources can be risky and requires a lot of capital. However, the O&G industry has acquired extensive know-how and advanced techniques/technologies in areas such as digital well monitoring, hydraulic fracturing, directional drilling, and analysis [34]. These advancements can offer inestimable support and lessons learned applicable to the exploration and exploitation of natural hydrogen and geothermal energy-related resources.
Currently, directional drilling and related operations combine the most advanced technologies used for accessing hydrocarbon reservoirs [35]. This technology allows for the effective control of the well trajectory, making the drill bit reach a designated target along a defined path [36,37]. Directional drilling presents some advantages, including enhanced production efficiency and reduced total drilling costs. Additionally, this technique also provides improved task execution when exposed to ground environment limitations due to complex formations like mountains and urban areas [35,38].

3. Geothermal Energy

Recently, the high demand for energy and the focus on low-emission technologies have made geothermal energy a promising renewable source. It is clean, renewable, potentially inexhaustible, highly reliable, and presents relatively low environmental impacts. It is fair to mention that it can be considered exempt from price volatility and can operate year-round, i.e., being weather-independent [39,40]. In this context, geothermal energy systems are an alternative support achieving the net-zero carbon emission target [41].
Deep geothermal energy, and geothermal energy in general, refers to using the heat (energy) naturally found in the subsurface of the Earth [34,42,43]. The main driver in using or not using geothermal energy in a specific location largely depends on the specific demand, available temperature, and costs [44]. Geothermal wells can be divided into three types according to the temperature, namely (i) low temperature (less than 150 °C); (ii) medium temperature (between 150 and 200 °C); and (iii) high temperature (greater than 200 °C) [45]. Geothermal energy system plants use three main technologies for converting heat into electricity, where medium- or high-temperature resources are required [42,46].
  • Dry steam: Known as the most common technology, it uses steam at high pressure and temperatures (over 235 °C) to move a turbine paired with an electrical energy generator. After transferring its energy to the turbine, the steam condenses and is re-injected back into the Earth;
  • Flash: Water tanks (above 150–170 °C) are used to supply energy to single- or double-flash systems. The water is brought to the surface through wells, and due to the sudden pressure drop from the tank to the atmosphere, it separates into steam, which is directed to the plant, and liquid, which is then reinjected into the tank (single flash). If the geothermal fluid reaches the surface at extremely high temperatures, it can undergo the process twice (double flash).
  • Binary cycle: In tanks that generate water at moderate temperatures (between 120 and 180 °C), the geothermal fluid is used to vaporize a secondary liquid (typically isobutane or isopentane) through a heat exchanger, as this secondary fluid has a lower boiling point than water. The secondary fluid then expands in the turbine, condenses, and returns to the exchanger in a closed-loop system, with no interaction with the external environment.
Although the goals of the petroleum and geothermal industries are the same, there are differences in extracting these energy sources. Table 1 shows the main differences.
As shown in Table 1, there are differences in the extraction of petroleum and geothermal energy. One of the main differences is related to lithology. The most common types of formation rock in geothermal reservoirs are granite, quartzite, granodiorite, and greywacke [48]. These rocks are widely recognized for their hardness and abrasive nature [15]. Therefore, the main challenges in the exploration of geothermal resources are low ROP [49,50], high drill bit wear [49], and consequently low drill bit life [50].
Drilling fluid systems used in geothermal wells have evolved over the past decade and have been specifically designed to address the challenges encountered [51]. In geothermal wells, the high-temperature environment demands that drilling tools, fluids, and technologies resist high (or even extreme) temperatures, including the thermal limitations of drilling muds and directional drilling tools [34,52]. Some effects of high temperatures on drilling fluid performance are the degradation of chemical materials and undesired change in the rheological properties of the drilling fluid (in special bentonite-driven muds [1,53]), among others also impacting hole cleaning, filter cake formation, and general drilling hydraulics, which ultimately have effects on drilling parameters as well as in MSE and ROP [53].
Another important point is related to the diameter of the wells. Geothermal energy demands wells with higher diameters than petroleum. In addition, it is necessary to drill two wells to extract geothermal energy, while for oil, only one well is necessary.
There are approximately 3700 production wells in operation across the 198 geothermal fields worldwide. The countries with most wells operating are the United States of America (22.2%), Indonesia (14.1%), and the Philippines (11.5%) [54]. The economic viability of geothermal projects is heavily influenced by the costs associated with drilling operations. Typical costs for geothermal power plants range from 2000 USD/kW to 6000 USD/kW [10].

4. Natural Hydrogen

Parallel to geothermal energy, hydrogen is a clean, efficient, and flexible energy source [55]. Hydrogen, in the sense of an energy vector, is considerably versatile and applicable to different industry sectors, including construction and transportation, and it is a promising fuel [56,57]. Hydrogen can be produced from various sources, and Table 2 presents the most common color classification of hydrogen production by source.
Among the types of hydrogen, green, blue, and white hydrogen are the most sustainable. Green hydrogen is obtained from the electrolysis of water powered by renewable energy sources, while blue hydrogen is obtained through the steam reforming technique in which the CO2 produced is captured. Black/brown and gray hydrogen are obtained, respectively, by gasification and from steam reforming without CO2 capturing [59,60].
Black or brown hydrogen is the hydrogen generated through coal gasification, in which the black hydrogen is produced by bituminous coal and the brown hydrogen is produced by lignite coal. Gray hydrogen is the hydrogen produced from fossil fuels, primarily through steam gas reforming or coal gasification [61]. The black or brown hydrogen process generates approximately 19 tons of CO2 per ton of H2 (tCO2/tH2), while the gray hydrogen process generates between 10 and 19 tCO2/tH2. It is important to highlight that over 95% of the world’s hydrogen consumption is gray hydrogen [61].
Natural hydrogen, also known as geological hydrogen, native hydrogen, gold hydrogen, or white hydrogen [56,62], refers to hydrogen produced deep within the Earth in most cases but also shallower hydrogen that gets confined by impermeable barriers as it moves toward the atmosphere, much like how oil and gas has been trapped and stored over time [56,63]. Natural hydrogen is found in different geological environments and rock types, such as igneous rocks (mainly), sedimentary rocks, volcanic rocks, salt rock deposits, ore bodies, coal basins, kimberlites, and ultrabasic rocks, among others [62]. The formation of natural hydrogen can occur through various geological processes, including chemical and biological processes (e.g., radiolysis, serpentinization, decomposition of organic matter, direct H2O reduction, and fermentative processes, among others) [64].
Like natural gas extraction, the drilling process continues to be the main approach for accessing and producing natural hydrogen, with natural hydrogen reservoirs being trapped by impermeable layers and accessible through well drilling [65]. In terms of hydrogen, its low density, high diffusivity, and chemical/biological reactivity present new challenges to operational integrity and wellbore integrity safety. Safety may be challenged due to issues such as tubing/casing damage, contamination of steel structures [66], cement failure potentialization, and eventual excessive annular pressure accumulation, among others [65]. From the literature, ways under study and development that may solve issues with casing and tubing structures are the usage of materials such as aluminum and nickel alloys, which have less susceptibility to hydrogen-related contamination [67].
Natural hydrogen reserves were neglected and sometimes unnoticed for decades, since exploration-phase equipment was not designed for its detection and also because it was thought that it would not be storable (due to its diffusivity) or would not even have commercial value [56]. Nowadays, however, it is common sense that there are important and commercially reserves around the globe, and it has been suggested that approximately 20 Mt per year of hydrogen (from natural reserves) is already escaping from the Earth’s surface to the atmosphere [63].
Natural hydrogen accumulations have been found in the United States of America, Russia, Canada, Finland, Philippines, Australia, Oman, Turkey, Mali, and recently in Brazil, among other places [68,69]. This implies that natural hydrogen is generated on a global scale [62]. Natural hydrogen surface emanations, also known as fairy circles, form circular depressions that are visible on satellite images [70].
The village of Bourakebougou in Mali (Africa) was the first community where natural hydrogen has been commercially used [71,72]. The drilling campaign by PETROMA (now HYDROMA, Montreal, QC, Canada) in the Taoudeni Basin, between the years of 2017 and 2018, has verified the existence of a significant commercial extensive hydrogen player extending over kilometers [70,72]. This project began in 2011 after having an old water well uncemented (drilled in 1987). Starting with a pilot hydrogen production well (Bougou-1), several more wells having been drilled since, initiating a considerable wide hydrogen exploration/exploitation campaign [72].
According to [73], natural hydrogen has also been detected in the chromite mine of Bulqizë, Albania. Bulqizë is one of the biggest chromium extraction areas worldwide, recovering over 20 million tons of high-grade ore, averaging 35% (wt) Cr2O3. The mine is located within the Bulqizë Jurassic ultramafic massif, about 40 km northeast of Tirana, encompassing an expansive area of 370 km2. At least 200 tons of H2 is released from the mine galleries, making it one of the highest recorded flow rates of H2 to date [73].

5. Energy Forecasts and Matrix Analysis

The global energy consumption in the next years will be decided by complex and interconnected dynamics across sectors, regions, and time. In all cases, energy consumption has been increasing globally, also driven by demographic and macroeconomic trends [74]. Figure 1 shows forecasts of primary energy use by source of fuel (2022–2050).
According to Figure 1, the Energy Information Administration (EIA) forecasts for 2050 that global energy consumption will have increased (2022 reference) from 638 quadrillion British thermal units (quads) to 855 quads in 2050 (34%). Following the trend where renewable energy consumption is gaining increasing relevance in a global perspective, solar and wind energy sources have been growing faster than any other energy source. Non-fossil fuel share as a primary energy source tends to increase over the years, from 21% in 2022 to up to 34% in 2050. Natural gas consumption has been recording the most significant increase among fossil fuels, from 153 quads in 2022 to up to 241 quads in 2050, an increase of approximately 57% [74]. Figure 2 shows the global energy matrix in 2023.
The global energy matrix in 2023 was composed of oil (30.0%), coal (28.0%), natural gas (23.0%), biomass and waste (9.0%), nuclear (5.0%), renewables (3.0%), and hydroelectric (2.0%) [75]. As seen, nonrenewable sources such as oil, natural gas, and coal minerals played a fundamental role. Over the past century, numerous studies predicted the decline of the oil and gas industry due to resource depletion. However, advancements in technology and reduced production costs have led to the discovery of new hydrocarbon reservoirs, while innovations in exploration and extraction techniques have made it possible to tap into unconventional and more challenging environments [76]. Figure 3 details a map with a global perspective showing the known largest O&G reserves, and Figure 4 shows the most relevant producers worldwide (2023).
Globally, it is fair to indicate the total proven oil reserves to be, in 2023, 1777.06 billion barrels (Bbbl). Most parts of the reserves are located in Venezuela (303.00 Bbbl), Saudi Arabia (267.23 Bbbl), Iran (208.60 Bbbl), Canada (189. 49 Bbbl), Iraq (145.01 Bbbl), the United Arab Emirates (113.00 Bbbl), Russia (107.79 Bbbl), Kuwait (101.50 Bbbl), the United States (50.94 Bbbl), and Libya (48.36 Bbbl). The relevant oil producers worldwide, as of 2023, are detailed in Figure 4.
As shown in Figure 4, the USA led oil production in 2023, with an average of 12.90 MMbbl/d. Brazil was the eighth largest oil producer, producing approximately 3.40 MMbbl/d. This fact was only possible due to the discovery of the pre-salt accumulations in 2006 in Brazil [78]. Although both “MM” and “M” represent millions depending on the reference and system in use, the petroleum industry conventionally uses “MM”, as in MMbbl (million barrels of oil), while the International System of Units (SI) uses “M”, as in MW (megawatts) to denote power. Figure 5 shows Brazil’s oil production over the years, from 2012 until the second quarter of 2024.
The pre-salt carbonate reservoirs in Brazil represent one of the most important petroleum accumulations in the world [20,78]. In March 2024, the total production of oil in Brazil was approximately 3.35 MMbbl/d. Pre-salt production was responsible for 2.62 MMbbl/d, i.e., pre-salt production corresponded already to more than 75% of total production in Brazil [80].
According to the Ten-Year Energy Expansion Plan (PDE) 2031 from the Brazilian Public Energy Research Company (EPE), publicized in 2022, oil production in Brazil is expected to grow in the next years. It is expected to reach a total production in Brazil of about 5.20 MMbbl/d in 2029, driven mostly by the intention to increase the rate of production from the pre-salt fields in Brazil [81].
In recent decades, growing concerns about gas emission rates and their effects on the climate have prompted a global transformation in energy sources [82]. Figure 6 shows the countries that produced the most carbon dioxide (CO2) in 2023.
In the world, approximately 39.02 billion of tons (Gt) of CO2 was emitted in 2023 [84]. Countries that most emitted CO2 in 2023 were China (11.90 billion metric tons—Gt), the United States (4.91 Gt), and India (3.06 Gt). Brazil was the twelfth largest CO2 emitter, producing approximately 0.48 Gt in the same year [83]. China, for example, has set ambitious goals to limit CO2 emissions by 2030 and achieve carbon neutrality by 2060, demonstrating a compromise to combatting climate change [13,85]. Figure 7 shows the total global CO2 emissions by sector in 2023.
According to Figure 7, the largest sources of CO2 emissions in 2023 were the power industry (14.92 Gt), transportation (8.23 Gt), industrial combustion (6.40 Gt), buildings (3.41 Gt), industrial processes (3.21 Gt), and fuel exploitation (2.66 Gt). The power industry was the largest contributor to CO2 emissions with an increase of 1.6% in 2023 [84]. To reduce CO2 emissions, large investments in renewable energy have been made in recent years, Figure 8 shows the energy investment in clean energy and fossil fuels.
According to Figure 8, USD 1740 billion was invested in clean energy and related industries in 2023. Investments were realized in renewable power sources (USD 659 billion), improvements in energy efficiency (USD 377 billion), grid systems (USD 331 billion), electric vehicles (USD 129 billion), battery storage (USD 37 billion), nuclear (USD 63 billion), and low-emission fuels and CCUS (USD 26 billion), among others. According to analyses developed by the Working Group on Renewable Energy Statistics (AGEE-Stat) in 2023, around 272.4 Terawatt hours (TWh) of renewable energy was generated, an increase of 7% compared to 2022 [86].
Energies 18 01608 g008
Figure 8. Global energy investment in clean energy and fossil fuels. Source: adapted from [87].
Figure 8. Global energy investment in clean energy and fossil fuels. Source: adapted from [87].
Energies 18 01608 g008
Brazil’s energy matrix, despite the large amount of oil and natural gas produced, is more renewable and cleaner on a global scale [88]. The renewable energy sources in Brazil reached 47.4% in 2022, an increase of 2.6% compared to 2021. This fact occurred due to the expansion of hydroelectric power, growth in wind and solar power generation, and other renewable sources such as black liquor, biogas, and biomass [89]. This fact is important due to the need to reduce GHG emissions. Figure 9 shows the Brazilian energy matrix.
The Brazilian energy matrix in 2022 was divided into nonrenewables (52.6%) and renewables (47.4%). The main nonrenewable sources were oil and derivates (35.7%), natural gas (10.5%), coal mineral (4.6%), and nuclear (1.3%). The main renewable sources were sugarcane biomass (15.4%), hydro (12.5%), and wind and solar (3.5%), among others. Figure 10 shows the primary energy consumption in the United States (reference: 2022).
In 2022, renewable energy provided about 13% of all energy consumption in the United States (13.18 Btu) [91]. The main renewable energy source used was biomass (4.9%). Geothermal energy holds a unique place among renewable energy. However, it remains a small contributor, and it is overshadowed by other renewable energy sources [43]. Figure 11 shows the installed geothermal energy capacity over the years with a global perspective (megawatts—MW).
Geothermal installed capacity worldwide has continued to grow in the last decade [10]. The total installed geothermal capacity in 2023 was approximately 16,335 MW. Between 2010 and 2020, the medium cost of electricity from geothermal power projects averaged between USD 0.049 and USD 0.085 per kWh [46]. Figure 12 shows the geothermal cumulative installed capacity worldwide in 2023.
The countries with the biggest cumulative installed capacity of geothermal energy as of the year-end in 2023 were the United States (3900 MW), Indonesia (2418 MW), the Philippines (1952 MW), Turkey (1691 MW), New Zealand (1042 MW), Kenya (985 MW), Mexico (976 MW), Italy (916 MW), Iceland (754 MW), and Japan (576 MW) [93]. In 2022, the heat and power sector in the United States employed 1539 [94]. Figure 13 shows the geothermal power units operating, pre-construction, and construction, as well as the announcements.
Currently, distributed in 37 countries, there are 353 geothermal power units in operation, 35 in pre-construction, 93 in construction, and 45 announced [95]. The main geothermal projects in the world are shown in Table 3.
The Geysers Geothermal Complex is located in California (United States) and covers an area of approximately 78 km2. It is the world’s largest geothermal field in the world, consisting of 22 geothermal power plants with a total installed capacity of 1517 MW. With the first plant commissioned in 1913, the Larderello Geothermal Complex is one of the oldest geothermal plants in the world. The complex is located in central Italy and comprises 34 plants with a total capacity of 770 MW of electricity generation. Moreover, the geothermal reservoir depths range from 700 m to 4000 m below the surface. The Cerro Prieto Geothermal field is located in the northern part of Mexico. The initial plant started operating in 1973, while the fourth plant was put into service in 2000. A fifth plant, equipped with two 50 MW turbines, is presently under construction. The power station features four plants, comprising 13 units and 720 MW of capacity [96].
Parallel to geothermal energy, hydrogen exploration and production could offer a significant opportunity to reduce GHG emissions while ensuring a sustainable energy supply [12]. Figure 14 shows the hydrogen demand worldwide from 2019 to 2021 and a forecast for 2030.
Global hydrogen demand reached 94 Mt (million metric tons) in 2021, and it is expected to double by 2030, reaching a total of 180 Mt [56]. Hydrogen was mainly used in the processes of refining (42.0%), ammonia (34.0%), methanol (15.0%), and iron and steel (6.0%). Currently, most of hydrogen production comes from fossil fuels, i.e., natural gas and coal [70,98]. From 94 Mt of hydrogen produced in 2021, only 0.04% was produced from water electrolysis using renewable energy sources [99]. Producing green hydrogen through water electrolysis is seen as the main method of hydrogen production; however, the current cost remains relatively high [62]. Figure 15 shows the hydrogen production cost in 2022–2023 and projections for 2060.
According to Figure 15, natural hydrogen (white hydrogen) was the lowest-cost method of production of hydrogen in 2022–2023 and will remain in 2060. Hydrogen production costs were as follows: white hydrogen (less than USD 2 per Kg), gray hydrogen (range of USD 1 to USD 3 per Kg), blue hydrogen (range of USD 2 to USD 5 per Kg), and green hydrogen (range of USD 4.5 to USD 6 per Kg). In addition, white and green hydrogen emit less than 1 Kg CO2e (carbon dioxide equivalent) per Kg H2, while blue and gray hydrogen produce 3 and 9 Kg CO2e per Kg H2, respectively [100]. However, over time, it is expected that the costs associated with electrolyzes will decrease because solar electricity will become cheaper and raw material costs in fossil fuel reforming will increase, favoring electrolysis [56]. Figure 16 shows the global hydrogen production in the sustainable development scenario (2019–2070).
It is expected that by 2070, hydrogen production will suffer a gradual transformation, with the majority being generated from electricity sourced from renewable energies and fossil fuels associated with CCUS [58]. It is expected to produce the following amount of hydrogen in 2070: 31 Mt of fossil hydrogen (produced from fossil fuels) without CCUS, 213 Mt of fossil hydrogen with CCUS, and 291 Mt of low-carbon electricity [101]. This gradual change will occur due to several key factors. The main factor is the electrolysis cost reduction, with solar panel costs expected to decrease by 40% and turbine costs by 27%. With advancements in turbine size and solar panel technologies, annual operating hours could increase by 10 to 30% depending on the technology and region. Additionally, the capital costs of electrolyzers are projected to drop by 25 to 30% as financial risks continue to decrease. The growing demand for low-carbon energy in sectors like steel production, ammonia manufacturing, and aviation will further drive adoption. Policy and regulatory support will accelerate this change through subsidies, carbon pricing, and incentives promoting renewable hydrogen. Finally, energy security concerns and market changes will encourage countries to reduce reliance on fossil fuel imports by investing in domestic renewable hydrogen production, solidifying its role in the global energy landscape. Thus, the global average cost of green hydrogen, which was USD 5 per kg in 2020, is expected to reach USD 2 per kg [102]. Figure 17 shows the forecast hydrogen demand worldwide in a sustainable development scenario from 2019 to 2070 by sector.
From the perspective of hydrogen demand, it is expected that the energy applications of hydrogen and its byproducts will become dominant, particularly as fuel for the transportation sector. In contrast, the use of hydrogen in the refining sector is projected to decline over this period [58]. All hydrogen produced in 2019 was used in industry (32.6 Mt) and refining (38.4 Mt). However, in 2070, this scenario will be changing, i.e., the main hydrogen demand will be transportation (158.2 Mt), synfuel production (121.5 Mt), power (72.9 Mt), industry (77.7 Mt), ammonia production (53.6 Mt), buildings (27.4 Mt), and refining (7.8 Mt).
To achieve net-zero emissions by 2050, the world will need to invest approximately USD 700 billion in hydrogen by 2030. Globally, the industry has announced 680 large-scale hydrogen project proposals in 2022, equivalent to USD 240 billion in direct investment through 2030 [104]. Of the USD 240 billion announced, about 65% is to clean hydrogen supply, 25% for end use, and 10 to transmission and distribution. However, only about 10% has reached the final investment decision or is under construction or operation. Europe leads, with over 30% of the proposed hydrogen investment globally [104].
Hydrogen production in Latin America from electrolysis could reach almost 6.0 Mt by 2030 due to announced projects, particularly in Chile (which accounts for 45.0% of the electrolytic hydrogen production of the announced projects in Latin America), as well as in Brazil and Argentina (which together represent 30.0% of the production) [105]. Investments announced in plants for green hydrogen production in Brazil total more than USD 25 billion [106]. In addition, Petrobras will invest nearly R$ 20 million in research about the processes for generating and extracting natural hydrogen in Brazil [107]. Figure 18 shows the hydrogen production projects in Brazil.
Most of the investments are concentrated in the following ports: Port of Pecém (Ceará), Suape (Pernambuco), and Açu (Rio de Janeiro). The industrial port complexes combine strategic factors for the advancement of the hydrogen supply chain, including access to industrial hubs, logistics for export, and proximity to renewable energy sources [106]. The projects in Brazil, which total 12,921 MW and 2237 Kt per year of hydrogen production by 2030, are divided into the concept, demonstration project, feasibility study, construction, and operation [109]. These investments are part of the 2023–2025 Triennial Work Plan of the National Hydrogen Program, which defines the strategies for Brazil based on three timeframes as follows: (i) by 2025, establish pilot plants for low-carbon hydrogen throughout the country; (ii) by 2030, position Brazil as a competitive producer of low-carbon hydrogen; (iii) by 2035, develop and solidify low-carbon hydrogen hubs in Brazil [105].

6. Conclusions

The transition to renewable energy is crucial for reducing carbon emissions and combating climate change. Geothermal and natural hydrogen exploration/exploitation represent promising avenues for diversifying the global energy matrix. In 2022, fossil fuels dominated the global energy landscape, contributing significantly to CO2 emissions. However, substantial investments in renewable energy recently indicate a shift toward cleaner energy sources.
Geothermal energy, with its ability to provide a stable and weather-independent power supply, is a viable renewable energy source. Despite the challenges associated with drilling in high-temperature and hard rock formations, advancements in drilling technologies can guarantee efficient and optimized operations and reduce costs, making geothermal energy more competitive.
Natural hydrogen, although in its nascent stages, shows potential for becoming a major energy source. The geoscience-related processes that produce and accumulate natural hydrogen and the technology and knowledge transfer from the oil and gas industry, especially from the drilling discipline, can facilitate its extraction. The increasing global interest and investments in hydrogen projects underscore its global significance.
Overall, the exploration and development of geothermal and natural hydrogen resources are essential for reaching a sustainable and low-carbon future. The continued advancement of drilling technologies will play a vital role in making these energy sources economically feasible and sustainably explored, contributing to the global effort to reduce carbon emissions and deal with climate changes.
As a continuation of this specific research, the next step will be a more detailed look at drilling techniques and technologies in addition to advances in know-how, focusing on comparisons across the specificities and differences in drilling operations for access to different natural energy resources.

Author Contributions

Conceptualization, D.Z.M.; methodology, D.Z.M. and A.N.; formal analysis, D.Z.M. and A.N.; writing—original draft preparation, D.Z.M.; writing—review and editing, A.N., J.D.H., M.H.M. and M.R.; supervision, A.N. All authors have read and agreed to the published version of the manuscript.

Funding

This study was financed, in part, by the São Paulo Research Foundation (FAPESP), Brazil. process number 2024/10600-0; by the Human Resources Program from the National Agency of Petroleum, Natural Gas and Biofuels (PRH-ANP) through the PRH-ANP/FAPESP 34.1 FEG/UNESP, Brazil; by the National Council for Scientific and Technological Development (CNPq), Brazil; by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)—Finance Code 001, Brazil; and by the Alexander von Humboldt Foundation (AvH), Germany.

Conflicts of Interest

The authors declare no conflicts of interest.

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  102. Hydrogen Forecast to 2050. Available online: https://www.dnv.com/focus-areas/hydrogen/forecast-to-2050/ (accessed on 26 November 2024).
  103. Forecast Hydrogen Demand Worldwide in a Sustainable Development Scenario from 2019 to 2070, by Sector. Available online: https://www.statista.com/statistics/760001/global-hydrogen-demand-by-sector-sustainable-scenario/ (accessed on 29 November 2024).
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  106. Hidrogênio de Baixo Carbono: Oportunidades Para o Protagonismo Brasileiro Na Produção de Energia Limpa. Available online: https://web.bndes.gov.br/bib/jspui/bitstream/1408/22665/1/PRLiv_Hidrog%C3%AAnio%20de%20baixo%20carbono_215712.pdf (accessed on 30 November 2024).
  107. Petrobras Investirá R$ 20 Milhões Em Pesquisas Sobre Hidrogênio Natural. Available online: https://agencia.petrobras.com.br/w/sustentabilidade/petrobras-investira-r-20-milhoes-em-pesquisas-sobre-hidrogenio-natural (accessed on 30 November 2024).
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Figure 1. Global projection of primary energy use by source of fuel (2022–2050). Note: biofuels are included in the “other renewables”; LM = low-economic-growth case; LZ = low-zero-carbon-technology-cost case; LP = low oil price; REF = reference case; HP = high-oil-price case; HZ = high-zero-carbon-cost case; HM = high-economic-growth case. Source: adapted from [74].
Figure 1. Global projection of primary energy use by source of fuel (2022–2050). Note: biofuels are included in the “other renewables”; LM = low-economic-growth case; LZ = low-zero-carbon-technology-cost case; LP = low oil price; REF = reference case; HP = high-oil-price case; HZ = high-zero-carbon-cost case; HM = high-economic-growth case. Source: adapted from [74].
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Figure 2. Global energy matrix in 2023. Source: adapted from [75].
Figure 2. Global energy matrix in 2023. Source: adapted from [75].
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Figure 3. Global oil reserves in 2023, organized by continent. Source: adapted from [75].
Figure 3. Global oil reserves in 2023, organized by continent. Source: adapted from [75].
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Figure 4. World’s biggest oil producers in 2023 per country (MMbbl/d). Source: adapted from [77].
Figure 4. World’s biggest oil producers in 2023 per country (MMbbl/d). Source: adapted from [77].
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Figure 5. Brazil’s oil production over the years from 2006 to date (MMbl/d). Source: adapted from [79].
Figure 5. Brazil’s oil production over the years from 2006 to date (MMbl/d). Source: adapted from [79].
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Figure 6. Countries that produced the most CO2 in 2022. Source: adapted from [83].
Figure 6. Countries that produced the most CO2 in 2022. Source: adapted from [83].
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Figure 7. Global CO2 emissions by sector in 2023. Source: adapted from [84].
Figure 7. Global CO2 emissions by sector in 2023. Source: adapted from [84].
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Figure 9. Brazilian energy matrix in 2022. Source: adapted from [89].
Figure 9. Brazilian energy matrix in 2022. Source: adapted from [89].
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Figure 10. U.S. primary energy consumption by energy source in 2022. Source: adapted from [90].
Figure 10. U.S. primary energy consumption by energy source in 2022. Source: adapted from [90].
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Figure 11. Installed geothermal energy capacity around the world (MW) over the years. Source: adapted from [92].
Figure 11. Installed geothermal energy capacity around the world (MW) over the years. Source: adapted from [92].
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Figure 12. Geothermal cumulative installed capacity worldwide in 2023 (MW). Source: adapted from [93].
Figure 12. Geothermal cumulative installed capacity worldwide in 2023 (MW). Source: adapted from [93].
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Figure 13. Geothermal power units (May, 2024). (a) Operating; (b) pre-construction and construction; (c) announced. Source: adapted from [95].
Figure 13. Geothermal power units (May, 2024). (a) Operating; (b) pre-construction and construction; (c) announced. Source: adapted from [95].
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Figure 14. Hydrogen demand worldwide from 2019 to 2021 and a forecast for 2030. Source: adapted from [56,97].
Figure 14. Hydrogen demand worldwide from 2019 to 2021 and a forecast for 2030. Source: adapted from [56,97].
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Figure 15. Hydrogen production costs. Source: adapted from [100].
Figure 15. Hydrogen production costs. Source: adapted from [100].
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Figure 16. Global hydrogen production in the sustainable development scenario, 2019–2070. Source: adapted from [101].
Figure 16. Global hydrogen production in the sustainable development scenario, 2019–2070. Source: adapted from [101].
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Figure 17. Forecast hydrogen demand worldwide in a sustainable development scenario from 2019 to 2070 by sector. (a) Million metric tons; (b) percentage. Source: adapted from [103].
Figure 17. Forecast hydrogen demand worldwide in a sustainable development scenario from 2019 to 2070 by sector. (a) Million metric tons; (b) percentage. Source: adapted from [103].
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Figure 18. Hydrogen production projects in Brazil. Source: adapted from [108].
Figure 18. Hydrogen production projects in Brazil. Source: adapted from [108].
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Table 1. Comparison between petroleum and geothermal energy.
Table 1. Comparison between petroleum and geothermal energy.
PetroleumGeothermal
Temperature150–175 °C (hot)150–350 °C
Flow rates5000 bpd (high flow)50,000 bpd (average)
Drilling5–7″
Onshore/offshore
Vertical and long reach horizontal		8–12″
Onshore
Vertical (less common)/deviated (most common)
ProductionHigh initial flow (months)
Declining rate (years)		Constant production
20–30 years
LithologySedimentaryVolcanic, intrusive, metamorphic
FaciesStratigraphic/structuralComplex fault-dominated
Source: adapted from [47].
Table 2. Color classification of hydrogen by source of production and respective colors.
Table 2. Color classification of hydrogen by source of production and respective colors.
ColorClassificationDescription
Black hydrogenProduced from coal (anthracite) gasification without CCUS
Brown hydrogenProduced from coal (lignite) gasification without CCUS
Gray hydrogenProduced from methane steam reforming without CCUS
Blue hydrogenProduced from methane steam reforming with CCUS
Green hydrogenProduced from water electrolysis with renewable power source
White hydrogenProduced from natural reservoirs/accumulations; originated from geological reactions (natural occurrence)
Turquoise hydrogenProduced from methane pyrolysis (carbon results as a solid byproduct)
Moss hydrogenProduced from biomass or biofuels via catalytic reforming or anaerobic digestion and from gasification of plastic waste
Pink hydrogenProduced from water electrolysis with nuclear power source
Note: carbon capture, utilization, and storage (CCUS). Source: [58].
Table 3. The main geothermal projects.
Table 3. The main geothermal projects.
ProjectsLocalizationInstalled Capacity
The Geysers Geothermal ComplexUnited States1517 MW
Larderello Geothermal ComplexItaly770 MW
Cerro Prieto Geothermal Power StationMexico720 MW
Makban Geothermal ComplexPhilippines458 MW
CalEnergy Generation’s Salton Sea Geothermal PlantsUnited States340 MW
Hellisheidi Geothermal Power PlantIceland300 MW
Tiwi Geothermal ComplexPhilippines289 MW
Darajat Power StationIndonesia260 MW
Malitbog Geothermal Power StationPhilippines230 MW
Wayang Windu Geothermal Power PlantIndonesia225 MW
Source: adapted from [96].
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Nascimento, A.; Mantegazini, D.Z.; Mathias, M.H.; Reich, M.; Hunt, J.D. O&G, Geothermal Systems, and Natural Hydrogen Well Drilling: Market Analysis and Review. Energies 2025, 18, 1608. https://doi.org/10.3390/en18071608

AMA Style

Nascimento A, Mantegazini DZ, Mathias MH, Reich M, Hunt JD. O&G, Geothermal Systems, and Natural Hydrogen Well Drilling: Market Analysis and Review. Energies. 2025; 18(7):1608. https://doi.org/10.3390/en18071608

Chicago/Turabian Style

Nascimento, Andreas, Diunay Zuliani Mantegazini, Mauro Hugo Mathias, Matthias Reich, and Julian David Hunt. 2025. "O&G, Geothermal Systems, and Natural Hydrogen Well Drilling: Market Analysis and Review" Energies 18, no. 7: 1608. https://doi.org/10.3390/en18071608

APA Style

Nascimento, A., Mantegazini, D. Z., Mathias, M. H., Reich, M., & Hunt, J. D. (2025). O&G, Geothermal Systems, and Natural Hydrogen Well Drilling: Market Analysis and Review. Energies, 18(7), 1608. https://doi.org/10.3390/en18071608

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