Natural Gas

Sally Benson, at AGCI's 2016 Getting Near Zero workshop, describes opportunities for carbon capture and storage, including those for natural gas.

Xiaochun Zhang reviews some key factors in assessing climate benefits of using natural gas vs. coal for electricity.

Dale Simbeck speaks at AGCI workshop Energy Options and Paths to Climate Stabilization

Natural gas supplied approximately 23% of the total global primary energy supply in 2017 [BP, 2018].

In 2017, natural gas production in OECD countries grew by 2.4% compared to 2016. Production increased by 17.7% in Asia Oceania, 1.1% in Americas, and 0.4% in Europe [IEA, 2018].

By energy source, natural gas accounts for the largest increase in world primary energy consumption [EIA & DOE, 2016]. Global natural gas-fired power generation increased by 2.2% in 2014. This is generally in line with the annual growth rate needed to achieve the 2025 2DS target of 2.4 % [OECD/IEA, 2017].

Natural gas-fired power generation is an increasingly valuable alternative to coal-fired generation and can provide flexibility in supporting the integration of renewables [OECD/IEA, 2017].

Imminent Breakthroughs

Conventional Gas

• Natural gas plays the important role of facilitating a transition to low-carbon electricity generation in the Energy Technology Perspectives 2°C Scenario (2DS) [OECD/IEA, 2016].

• Companies are pursuing a technique known as the 'Super Frac' to make more cracks at smaller intervals throughout the wellbore, maximizing the efficiency of drilling [Puko, 2014].

• Gas turbine design focuses on flexibility performance of new-build plants and retrofits of existing plants. Ramping capabilities, start-up times, turndown ratios and part-load behavior are being developed with moderate full-load efficiency improvements [OECD/IEA, 2017].

• State-of-the-art combined-cycle gas turbine (CCGT) efficiency now exceeds 60%. It is expected to improve to 65% efficiency over the next decades [OECD/IEA, 2017].

Shale Gas

• Some companies are experimenting with biodegradable hydraulic fracturing fluid to help reduce concerns about water contamination around mining wells [Michalski & Ficek, 2016].

• CO2-based fluid is used as an alternative working fluid to reduce the GHG emissions and water consumption of the fracking process. Research shows this CO2-based fluid could reduce GHG emissions by 400% and water consumption by 80% when compared to conventional water-based fluids, however they require a 44% increase in energy consumption [Wilkins et al., 2016].

• Shale gas is projected to grow in the next few years. The demand of shale gas is expected to grow by 1.6% annually for the next five years, and reach consumption of nearly 4,000 bcm by 2022, up from 3,630 bcm in 2016. The U.S. takes the lead on its global supply by the second shale revolution [OECD/IEA, 2017b].

• There are many countries and regions that are expected to contribute to the boost in offshore gas output, from Brazil to Australia to the Eastern Mediterranean; however, the most growth is seen in the Middle East, with continued development of the world’s largest gas field [Davis, 2018].

Coal Seam Gas

• The coal seam gas (CSG) industry is only around 30 years of commercial production, which is relatively new in the history of the energy sector. In two decades coal seam gas has come to account for 30% of gas production in Australia [Evershed, 2018].

• The United States is the top producer, producing 70–80% of world’s coal seam gas [Hamawand et al., 2013].

• Coal seam gas is expected to be used for 100 years based on current production rates, which is higher than petroleum products, black coal, and conventional gases [Hamawand et al., 2013].

• Membrane filtration technologies are important in the treatment of produced water [Abousnina et al., 2015].

• The greater effectiveness of enhanced coalbed methane (ECBM) has been identified as higher CBM recovery with minimal pollution risk compared to traditional pressure depletion and hydraulic stimulation techniques. It also has the ability to contribute to CO2 sequestration [Zhang et al., 2016].

Methane Hydrates

• Modeling studies are underway to better understand the chemical and physical controls on hydrate formation, behavior and dissociation. A new method is being developed to achieve rapid methane hydrate formation in an unstirred tank reactor configuration (UTR) at moderate temperature and pressure conditions employing tetrahydrofuran (THF) as a promoter [Veluswamy et al, 2016].

• The Submarine Gas Hydrate Deposits (SUGAR) project expanded the knowledge and application of gas hydrates. This project facilitates to the development of new technologies for gas hydrate exploration, production and environmental monitoring [Helmholtz Association of German Research Centres, 2018].

Obstacles to TW-Scale Integration

Conventional Gas

• Geopolitical conflict and other above ground factors can constrain natural gas exploration and exploitation [EIA, 2016a].

• Worldwide, coal seam gas is a major source of energy that is estimated to be around 256 Tm3 [Hamawand et al., 2013]. However, the economic viability of gas recovery is restricted to the cost of extraction and gas prices [Reig et al., 2014].

Shale Gas

• The economic viability of gas recovery depends on three factors: the cost of drilling and completing wells, the amount of gas produced from the well in its lifetime, and the prices received for producing the gas [EIA, 2016b].

• Limited availability of freshwater could become a stumbling block for rapid development of shale resources through hydraulic fracturing [WRI, 2014].

• Lack of infrastructure and limited pipeline access become the major obstacles for shale gas to be extracted and transported [Malik, 2018].

Coal Seam Gas

• Compared to conventional gas, the exploration of coal seam gas is expensive and inaccessible. Yet as conventional sources become more difficult to acquire, unconventional gas sources will become more important [CSIRO, 2015].

• The development of large-scale projects of coal seam gas in facing challenges such as remote locations, the number of wells being drilled, and the casing material [Kwikzip, 2017].

Methane Hydrates

• Methane hydrate is a promising energy source that has a carbon quantity twice more than all fossil fuels, however it is in solid form and therefore not easily accessed via current oil and gas recovery techniques [Chong et al., 2016]. There is also a high cost to use existing technologies to recover gas from gas hydrates, including dissociation and depressurization [Chong et al., 2016].

• There is also a high cost to use existing technologies to recover gas from gas hydrates, including dissociation and depressurization [Chong et al., 2016].

• Technical challenges are still the major barriers for exploration and exploitation of gas hydrate in many countries [Zhao et al., 2017]. 

• In addition, the economic efficiency of gas recovery and transportation issues during the extraction of resource is also a significant concern that hinder the large-scale development [Zhao et al., 2017].

Enabling Technologies

Conventional Gas

• Novel thermal coatings and cooling technologies are developed to enable higher temperatures and improve efficiencies [OECD/IEA, 2017].

• Conventional oil and gas use similar technology, and recent advances have facilitated extraction while making the process more efficient. Enabling technologies include: 3D and 4D seismic imaging technology uses seismic imaging and computers to create models of subsurface layers and observe subsurface characteristics over time [Naturalgas, 2013].

• Offshore drilling technology allows for access of deep water reserves of oil and gas and safety is improving in recent years [Abimbola, 2014].

• Measurement while drilling (MWD) can be used for data collection from a well while gas is being extracted, allowing for detailed information on the nature of the well. This can increase efficiency and accuracy in the drilling process [Naturalgas, 2013; Chin et al., 2014].

• Coiled tubing drilling (CTD) has replaced the traditional jointed drill pipe which has been widely adopted as a cost-effective re-entry strategy [Cedilo et al., 2015].

Shale Gas

• One of the promising future fracturing technologies is to use non-aqueous working fluids including supercritical CO₂ and natural gas. They could be applied to wells that have reached a low-level asymptotic production [Middleton et al., 2017]. 

• Hydraulic fracturing (Figure 1) and horizontal drilling has revolutionized the role of shale gas in the overall energy economy [Fracfocus, 2010].

• Shale gas can be accessed due to improvements of slick-water fracturing and multi-stage fracturing [Gandossi, 2013].

Figure 1. Risks associated with hydrofracking for shale gas. From Howarth et al., 2011

Coal Seam Gas

• There are different ways of extracting natural gas from coal seams, among which vertical drilling and horizontal (directional) drilling are the main ways [NSW].

• Hybrid drill rigs and hydraulic fracturing technology allows for the extraction of coal seam gas with more efficiency and less cost [Huddlestone-Holmes et al., 2015].

• Microbial technologies are used to enhance CSG production via facilitating the conversion of carbon dioxide (CO2) to methane and providing additional capacity for geological CO2 storage [CSIRO, 2015].

• A dual reverse osmosis system is proposed to enhanced water recovery in the coal seam gas industry [Blair et al., 2017].

Methane Hydrates

• Thermal stimulation, depressurization and inhibitor injection are the three most commonly proposed and studied techniques in dissociating methane hydrates [Chong et al., 2016].

• To extract and utilize energy from methane hydrates effectively, electromagnetic heating and in situ combustion are the two main heat transfer approaches [Chong et al., 2016].

• There are several considerations hindering large-scale commercial exploration of methane hydrates, including exploring with minimum environmental impacts, the possible loss of strength of pure methane hydrates, use of geological hydrate formations for CO2 storage, and the high cost of exploration [Chong et al., 2016].

Political Considerations

Conventional Gas

• Conventional natural gas becomes a strategic energy resource since it provides a reliable fuel with a delivery system, with less reliance on imported fossil fuels [Ríos-Mercado, 2015]; it is an important component of national energy independence [Knox-Hayes, 2013].

• Natural gas is changing from a marginal fuel consumed in disconnected markets into a standardized fuel in use in several markets around the world. With a projected share of total primary energy supply of 28% by 2030, natural gas trade is expected to influence geopolitical relations greatly [Baker Institute].

• Energy and infrastructure security would also be dictated by natural gas trading. In the US, given projections of LNG import requirements, gas transportation security is being seriously scrutinized [Baker Institute].

Shale Gas

• Local governments developed the shale gas in order to subsidize the national energy supply mix and global energy market [Reig et al., 2014].

• Public opposition still exists in using hydraulic fracturing for large-scale shale gas exploration due to its fresh water considerations and business risks [Reig et al., 2014].

• Economic recoverability is also a key consideration in shale gas exploration, including private ownership of subsurface rights, availability of independent operators and contractors, preexisting infrastructure, and the availability of water for hydraulic fracturing [Speight, 2016].

• The development of shale gas would have political benefits of energy security, broad-based economic development, and environmental strategy such as climate mitigation and air quality protection. However, the regulatory policies and investment are highly needed [Frazier, 2018].

Coal Seam Gas

• Competing stakeholders remain an issue [Jarrett, 2017]. People from different walks of life, like farmers and residents, worry about losing water rights or land use rights due to CSG exploration. [John, 2011].

Methane Hydrates

• Gas hydrate may make a significant difference in the energy structure after efforts on the commercialization [Zhao et al., 2017].

• Many countries developed the exploration of methane hydrates, since methane hydrates may be a new energy source for countries lacking access to conventional resources [Spalding & Fox, 2014].

• Methane hydrate is new source of wealth for richly endowed regions. However, it has raised issues about the real benefits and costs of resource extraction [Kiani et al., 2016].

Social Considerations

• Resource exploitation and exploration generates transient and permanent jobs, but health, public safety, and environmental considerations must be taken into account.

Conventional Gas

• Mineral extraction has a substantial economic and social impact, which is highly dependent on where the exploitation occurs. To maintain 'corporate social responsibility' and sustainable business practices, the mining industry has coded rules, such as those codes in the International Council on Mining & Metals (ICMM). Many gas companies have developed social, environmental and ethical policies [Jenkins and Yakovleva, 2006].

Shale Gas

• The exploration of shale gas has brought an influx of permanent and transient workers, leading to development activity and generated revenue [Small et al., 2014]. However, the influx of transient workers can also lead to more violence, accidents, and sexually transmitted disease in small communities [Ruddell et al., 2014; Hoban et al., 2014].

Coal Seam Gas

• There are some social impacts of gas development that people consider, including the rising cost of living in the area, the long-term impacts on groundwater, and how their community culture is affected [Phelan et al, 2017].

• The social risks and problems with CSG involve encroachment on good farming land, disruption of other land uses and industries, clearing of bushland, health impacts on workers and nearby residents [Lock the Gate Alliance, 2018]. 

Methane Hydrates

• Unconventional energy resources such as methane hydrate can bring important benefits in terms of employment, income, and trading gains [Kiani et al., 2016].

Environmental Considerations

• Natural gas is a relatively clean burning fossil fuel compared to crude oil and coal. The application of natural gas in electric power provisions, in both residential and industrial sectors, in part due to its smaller environmental toll [EIA, 2017].

Conventional Gas

• If collected correctly, natural gas is cleaner and more efficient than coal burning, emitting lower levels of sulfur dioxide, nitrogen oxide, carbon monoxide and mercury [Bergstrom & Randall, 2016]. However environmental concerns regarding water contamination and air pollution, as well as GHG emissions still exist [Howarth, 2014; Clark et al., 2013].

• Seismic surveys for exploration can result in habitat depletion, erosion, loss of vegetation and the expulsion of large amounts of greenhouse gases and dust particles [Barclays].

Shale Gas

• The expansion of shale gas mining has triggered intense public debates in terms of the potential environmental and human health effects from hydraulic fracturing [Vengosh et al, 2014]. It can cause fresh water resource depletion, both for ground water and surface water[Vengosh et al., 2014].

• Shale gas has a life cycle GWP equivalent of 412 – 1102 g CO₂ eq. per kWh as opposed to the range of 837 – 1132 g CO₂eq. per kWh for coal. Shale gas is mostly accepted as having reduced GHG emissions compared to coal, although a boom in shale gas in countries like the US has seen a decline in coal prices and resulting resurgence. Such a resurgence was observed in the UK in 2011-12 [Cooper et al., 206].

• Shale gas has a lower water footprint (m³/ TJ) than all forms of oil, biomass and coal. Conventional gas outperforms shale gas in this regard [Cooper et al., 2016].

• Waste-water management after shale gas exploration also remains an issue to be dealt with, in order to make assurances for making it a safe and reliable energy source [Lutz et al., 2013].

• The extracted water from reservoirs, along with pumped fracturing agents, collectively known as ‘flowback water’ usually contains radionucleotides and bromides dissolved. The concentration of these depend on the specific minerology of the rocks and would need to be considered in exploration projects [Cooper et al., 2016]

Coal Seam Gas

• Hydraulic fracturing to develop CSG reserves could lead to water contamination. Research also shows that contaminant concentrations in sediments are higher near mining sites. [Hamawand et al., 2013; Ali et al., 2018].

• The fugitive emissions of methane and carbon dioxide gases are also a major environmental impact of the CSG production [Hamawand et al., 2013], since methane is 72 times more powerful as a greenhouse gas than carbon dioxide.

• Mining of CSG would entail air pollution, contamination or depletion of ground or surface water, pollution of waterways, and potential damage to biodiversity [Lock the Gate Alliance, 2018]. 

• Methane hydrate exploration is faced with the potential challenge of a wide geographical distribution [Jackson, 2014]. `

• Compared to coal and oil, methane from hydrates is less carbon-intensive, producing half as much CO₂ per unit of combustion as coal [Masuda et al., 2018].

Methane Hydrates

• Methane hydrate could be a potential hazard to the marine ecosystem, component balance, atmosphere environment, and even global climate change [Zhao et al., 2017].

• The phase transition of methane hydrates from solid into gas potentially result in a seafloor instability and a following submarine landslide or even a tsunami [Zhao et al., 2017].

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