Methane Production from Gas Hydrate Deposits through Injection of Supercritical CO2Christian Deusner *, Nikolaus Bigalke, Elke Kossel and Matthias Haeckel *
GEOMAR, Helmholtz Centre for Ocean Research Kiel, Wischhofstr.1-3, D-24148, Kiel, Germany;
E-Mails:
nbigalke@geomar.de (N.B.);
ekossel@geomar.de (E.K.)
* Authors to whom correspondence should be addressed; E-Mails:
cdeusner@geomar.de (C.D.);
mhaeckel@geomar.de (M.H.); Tel.: +49-431-600-1415; Fax: +49-431-600-1400.
Received: 5 April 2012; in revised form: 5 May 2012 / Accepted: 7 June 2012 /
Published: 25 June 2012
Abstract: The recovery of natural gas from CH4-hydrate deposits in sub-marine and
sub-permafrost environments through injection of CO2 is considered a suitable strategy
towards emission-neutral energy production. This study shows that the injection of hot,
supercritical CO2 is particularly promising. The addition of heat triggers the dissociation of
CH4-hydrate while the CO2, once thermally equilibrated, reacts with the pore water and is
retained in the reservoir as immobile CO2-hydrate. Furthermore, optimal reservoir
conditions of pressure and temperature are constrained. Experiments were conducted in a
high-pressure flow-through reactor at different sediment temperatures (2 °C, 8 °C, 10 °C)
and hydrostatic pressures (8 MPa, 13 MPa). The efficiency of both, CH4 production and
CO2 retention is best at 8 °C, 13 MPa. Here, both CO2- and CH4-hydrate as well as mixed
hydrates can form. At 2 °C, the production process was less effective due to congestion of
transport pathways through the sediment by rapidly forming CO2-hydrate. In contrast, at
10 °C CH4 production suffered from local increases in permeability and fast breakthrough
of the injection fluid, thereby confining the accessibility to the CH4 pool to only the most
prominent fluid channels. Mass and volume balancing of the collected gas and fluid stream
identified gas mobilization as equally important process parameter in addition to the rates
of methane hydrate dissociation and hydrate conversion. Thus, the combination of heat
supply and CO2 injection in one supercritical phase helps to overcome the mass transfer
limitations usually observed in experiments with cold liquid or gaseous CO2.
1. Introduction Large amounts of natural gas, predominantly methane, are stored in gas hydrates in sediments
below the seafloor and the permafrost [1]. Current estimates of the global methane hydrate inventory
range between 1000 and 10,000 Gt of carbon [2–5]. Motivated by these results, gas hydrate research
activities worldwide center around the exploitation of this potential new energy resource. The methods
that are currently discussed to produce the methane from gas hydrates are generally derived from
standard techniques used in conventional oil and gas business, i.e., reduction of the pressure in the
reservoir and thermal stimulation, as well as injection of hydrate inhibitors, such as salt, to induce
dissociation of the gas hydrates [6]. In addition, the substitution of CH4 by CO2 as guest molecule in
the gas hydrate structure has been proposed as a more elegant production technology with respect to
greenhouse gas policies [7,8].
All of these methods have been studied in laboratory experiments to validate their feasibility as well
as in numerical simulations to gain first ideas about their applicability on reservoir scale. First
production tests were carried out in the permafrost reservoir of Mallik in northern Canada in 2002 [9]
as well as in 2008 [10]. Gas hydrates were successfully destabilized by injection of hot water and by
depressurization, respectively, producing limited amounts of CH4 gas over a few days. Further field
trials in 2012 will test the chemical exchange of methane in gas hydrates by injection of CO2 below the
permafrost of the Alaska North Slope [11] and the depressurization technique in the first offshore test
in the Nankai Trough [12,13].
Overall, the conclusions drawn from those studies are that thermal stimulation by injecting hot
water is slow and inefficient, whereas depressurization seems to be the more promising strategy [6].
However, due to the endothermic nature of gas hydrate dissociation, in the long run, the reservoir will
cool down, re-establishing stable conditions for gas hydrates and consequently, methane production
rates are expected to cease after some time [14,15].
Thus, being able to achieve stable and economic methane production rates will require a
combination of depressurization and methods (re)activating the methane hydrate reservoir.
One elegant way to activate the methane hydrate reservoir is the injection of CO2. Since CO2
hydrate is thermodynamically more stable than CH4-hydrate and both form structure-I, the exchange
reaction will proceed exothermically [16], adding heat to the system. Besides its attractiveness in
combining energy production with CO2 storage as a measure to mitigate further increases in
greenhouse gas emissions to the atmosphere, a technological advantage is that it sustains the integrity
and geo-mechanical stability of the sediments, thus reducing the potential risk of slope failures.
Several laboratory-based studies have shown the feasibility of the hydrate conversion reaction on
pure or sediment-dispersed gas hydrates and from molecular scale to volumes of a few liters (an
overview is given in Discussion). However, the overall reaction rate turns out to be quite sluggish and
the conversion is often incomplete. This results primarily from a shell of CO2-hydrate that forms
around the methane hydrate grain. Any further mass transport of CO2 into and CH4 out of the inner
core is drastically slowed down or even completely inhibited as analogous experiments with C2
H6 as attacking guest molecules have shown [17]. Moreover, excess water, as usually encountered in the
pore space of hydrate deposits, generally induces immediate CO2-hydrate formation blocking
permeable pathways for the gas exchange.
http://www.mdpi.com/1996-1073/5/7/2112/pdf--------------
Scientists probe atomic structure and dynamics of water under deep Earth extreme pressure and temperature conditions
08-03-2013
Water is one of the most studied materials on Earth and has been the focus of dedicated research for decades. Despite it being a very simple compound of two common elements, two hydrogen atoms and one oxygen atom, researchers still struggle to describe the unusual structure and dynamics of liquid water. Now, a team of scientists have used synchrotron radiation to reveal the microscopic structure of water under conditions of extreme pressure and temperature. The results were published on 11th March 2013 in the Proceedings of the National Academy of Sciences of the USA (PNAS).
http://www.esrf.eu/files/live/sites/www/files/news/general/water-gas/index_html/image.jpgLiquid water seen through an optical microscope during the experiment plus, on the right, a schematic sketch based on simulations of the molecular dynamics of liquid water. Image courtesy C. Sahle
When subject to extreme temperature and pressure, water exists in the so called super-critical state and exhibits a number of peculiar characteristics very different to those of the water that flows through our taps. In these extreme conditions, water becomes a very aggressive solvent, catalysing otherwise impossible chemical reactions like, for example, the oxidation of hazardous waste or the conversion of sewage into clean water and gases like hydrogen, methane, carbon dioxide and carbon monoxide.
Extremely high temperature and high pressure conditions can be found in the lower crust and upper mantle of the Earth. Here, the unique properties of super-critical water are believed to play a key role in the transfer of mass and heat as well as in the formation of ore deposits and volcanoes. Super-critical water is even thought to have contributed to the origin of life. Insight into the structural properties of water on an atomic scale are essential to understanding the role of liquid water in these processes.
The team of scientists from the Technische Universität Dortmund (Germany), the University of Helsinki (Finland), the Deutsches GeoForschungsZentrum in Potsdam, (Germany), and the European Synchrotron Radiation Facility (France), used X-ray spectroscopy on the ESRF's ID16 beamline to study the structural properties of water in the super-critical state.
The challenge that faced the research team was to study liquids and gases under extreme conditions of high temperature and high pressure. The high performance of ID16 in terms of high flux, energy resolution and highly focused beam was essential to the success of this unprecedented study.
Although conventional spectroscopic analysis techniques can provide key insights into the atomic structure of a substance, they are not well suited to studying water under super-critical conditions because of the complex environment needed to maintain water in this state.
The research exploited the ESRF's hard X-rays to access the oxygen K-edge in a complex environment finding that water evolves systematically from liquid-like to more gas-like at high temperatures and pressures.
Based on the close resemblance between the theoretical and measured data, the team was able to extract detailed information about the atomic structure and hydrogen bonding of water. They showed that according to the theoretical model, the microscopic structure of water remains spatially homogeneous throughout the range of examined temperatures and pressures.
"The unparalleled results obtained here are a good example of new possibilities open to the scientific community for experiments impossible to conduct with other techniques," says Laura Simonelli, scientist on ID20. "Recently, ID16 was upgraded and moved to ID20 where the beamline has been vastly improved in terms of intensity, beam focus, stability and energy resolution. The astounding new X-ray Raman spectrometer will give access to a novel signal to noise ratio with a very wide covering of solid angles."
Publication
Microscopic structure of water at elevated pressures and temperatures, C.J. Sahle, C. Sternemann, C. Schmidt, S. Lehtolab, S. Jahn, L. Simonelli, S. Huotari, M. Hakala, T. Pylkkänen, A. Nyrow, K. Mende, M. Tolan, K. Hämäläinen, M. Wilke, PNAS (2013);
dx.doi.org/10.1073
http://www.esrf.eu/news/general/water-gas/index_html--------
Wednesday, June 25, 2008
Geological Society of Nevada presentation - March 21, 2008
THE SERPENTOSPHEREsubmitted February 20, 2008
Stanley Keith 1, Monte Swan 1, Martin Hovland 2, Håkon Rueslåtten 3, Hans Konrad Johnsen 2 and Norman Page 4
1 MagmaChem Exploration, Inc, PO Box 950, Sonoita, AZ 85637
2 Statoil Hydro, Forusbeen 50, N-4035 Stavenger, NORWAY
3 Numerical Rocks, Stiklestadveien 1, N-7041, Trondheim, NORWAY
4 2649 N. Martin Ave, Tucson, AZ 85719
The Serpentosphere consists of an earth-wide nearly continuous layer (or spherical shell) of rock dominated by serpentine group minerals (serpentinite). The Serpentosphere is typically about two kilometers thick beneath ocean basins where it is mainly composed of lizardite. Beneath continents, the Serpentosphere is mainly composed of antigorite (alpine peridotite/serpentinite) and may be several kilometers thick. The base of the Serpentosphere coincides with the gravity and high-velocity seismically defined transition beneath both continents and ocean basins commonly referred to as the Moho. Beneath ocean basins and adjacent to spreading centers, oceanic Serpentosphere is continuously generated by the interactions of deep circulating marine composition water – partly in super-critical state – with harzburgitic peridotite in a process referred to as serpentinization. Conversion of the harzburgite to lizarditic serpentine under supercritical condition is texturally preservative and probably induces about 40% volume expansion. The volume expansion provides an excellent mechanism to expel and propel fluid products – including hydrocarbons – from the area of serpentinization to seep sites at the crust hydrosphere/atmosphere interface. A downward diffusing, super-critical serpentinization front is present beneath every ocean basin and is more active where it originally formed near oceanic ridge thermal anomalies. When oceanic Serpentosphere is subducted beneath continental or oceanic crust areas, it converts to antigorite-dominated serpentinite rock (generally coincident with greenschist facies metamorphism). During flat subduction, the relatively low-density antigorite ‘floats’ and is underplated to the base of the continental crust at the Moho geophysical interface.
In effect, both oceanic and continental Serpentospheres reflect a deep ‘weathering’ process that consists of the interaction of deep crustal and oceanic, water-dominated fluids with the upper portion of a mainly harzburgitic peridotite at the top of the earth’s lithospheric mantle. The process is analogous to the formation of the pedosphere through interactions of the earth’s hydrosphere-atmosphere layer with the top of the earth’s lithospheric crustal layer. In this context, the Serpentosphere may be viewed as a thin membrane that separates water-poor, life-free abiogenetic processes in the mantle from water-rich, life-related processes above the Serpentosphere in the oceanic crust.
The Serpentosphere has enormous and novel implications for four major geologic problems that are of current interest to the geologic and social community: the driving mechanism for plate tectonics, the origin of life, the origin of hydrocarbons, and contributions to global climate. A close relationship between trace elements in crude oils and serpentinite has been found. Migration of the serpentine-associated hydrocarbons to seep sites on the ocean floor and in subaqueous continental environments is essentially the base of the food chain for the biosphere and provides a nutrient and energy source for life in these environments. Heat, methane and carbon dioxide generated during the serpentinization reaction provide a major thermal and greenhouse effect to the earth’s hydrosphere-atmosphere system that is overlooked and underappreciated by the current global climate science. The ductility of the serpentine group minerals provides the tectonic "grease" that allows crustal plates to be able to slide and glide around on the earth’s crust at the Serpentosphere/Moho interface. Because Serpentosphere has been continuously generated since the beginning of geologic time it must be considered as one of the fundamental entities of our water-surfaced planet – the only water-planet we know of…
http://www.serpentosphere.blogspot.com/ ... evada.html-------------
Bacteria ate up all the methane that spilled from the Deepwater Horizon wellBy Ed Yong | January 6, 2011 3:00 pm
On April 20, 2010, a bubble of methane raced up the drill column of the Deepwater Horizon oil rig, bursting through the seals and barriers in its way. By the time it exploded on the platform’s surface, it had grown to 164 times its original size. The rig, severed by the explosion, caught fire and sank two days later, allowing oil and gas to spew into the Gulf of Mexico for 83 long days.
This chaotic methane bubble was just a vanguard. With the well unsealed, substantial amounts of the gas were released into the gulf. This plume of dissolved methane should have lurked in the water for years, hanging around like a massive planetary fart. But by August, it had disappeared. On three separate trips through the gulf, John Kessler from Texas A&M University couldn’t find any traces of the gas above background levels. He thinks he knows why – the methane was eaten by bacteria.
The gas pouring out of the broken well spurred the growth of bacteria called methanotrophs, which can break down methane as their only source of energy. They made short work of the gas. By the time that Kessler reached the gulf, just four months after the initial blowout, he found plenty of bacteria and precious little methane.
“Kessler’s paper is very nice work,” says Terry Hazen, who has studied how bacteria reacted to the Deepwater Horizon disaster. “I also suspected that methanotrophs would be active very quickly with this release of methane. We also have supporting data that we have not yet published… wish we had gotten ours out faster.“
Kessler’s discovery goes beyond last year’s disaster. It also tells us about what happens to methane bubbles that naturally rise from the deep ocean, all over the world. Within the ocean floor, methane lies trapped within cages of ice called methane clathrates (or methane hydrates). Methane naturally escapes from these deposits, as well as from undersea vents and natural oil or gas seeps. If the gas reaches the atmosphere, it could have serious effects on the planet’s climate. After all, methane is a potent greenhouse gas and undersea clathrates contain about twice as much carbon as all the fossil fuels in the world.
But first, the gas has to reach the atmosphere, and Kessler thinks that this is unlikely. While scientists can hardly release large bursts of methane to see what happens, they can rely on “natural experiments” like the unplanned surge that followed the Deepwater Horizon well. If that gas failed to make it past the gauntlet of underwater bacteria, then natural seeps would probably meet the same fate.
Some scientists have suggested that methane freed from clathrates could have contributed to the climate upheavals behind some of Earth’s greatest extinctions events, including the day when life nearly died – the Permian-Triassic extinction. *
Greg Retallack from the University of Oregon initially backed this idea, but his mind has since changed. “I love this paper as it signals the final break with my long love affair with methane clathrate release as a cause of [the Permian-Triassic] mass extinction,” he says. “It seems that marine methane cannot even make it out of the ocean because it’s rapidly consumed there.” **
Richard Camilli, who has studied the Deepwater Horizon oil plume, agrees. He says that Kessler’s conclusions probably apply to natural methane leakages, as well as to other oil spills too. “[It] is likely to become a classic reference,” he says.
In June, when David Valentine first described the plume of oil in the Gulf, he found that most of the methane was hanging in a layer between 800 and 1200 metres down. When Kessler arrived at the same area in late August, aboard the NOAA Ship Pisces, he found no traces of it. He did, however, find the degraded remnants of oil chemical and a suspiciously low amount of oxygen.
Many methane-eating bacteria use up oxygen to break down the gas, so Kessler reasoned that the microbes had done away with the methane. He even found the bacteria in question. In September, Kessler recovered several species of methane-eating bacteria from seven different sites. In some areas, these specialists made up a third of the local bacteria.
Back in June, the methane-eaters were nowhere to be found. Instead, Valentine and Hazen detected several other groups of bacteria that were breaking down other oil hydrocarbons, such as ethane and propane. They were first on the scene. Valentine predicted that other species would follow and mop up the methane, in “boom and bust cycles of bacterial succession”. He was right. By September, the bacteria that dominated the gulf in June had all but vanished and the methane-eaters had taken their place. Even they were no longer active – they were just the remnants of a population that had bloomed in July and August.
Hazen adds that the methane-eaters “have the ability to degrade over 300 other compounds,” and may have helped the clean-up efforts in the Gulf, beyond just breaking down the methane. He has been working on ways of turning this bacterial appetite to our advantage. In 1995, Hazen patented a process for seeding polluted groundwater with methane, to stimulate the growth of bacteria that would break down the other contaminants. Many companies around the world now use this process, enticing bacterial janitors with a methane menu.
Footnotes
* This scenario was the basis of one of the worst pieces about the Deepwater Horizon disaster – a frenzied article claiming that BP’s drilling operation “may have triggered an irreversible, cascading geological Apocalypse that will culminate with the first mass extinction of life on Earth in many millions of years.” It was ably debunked.
** It’s possible that the Permian-Triassic event might have involved methane in such large amounts that it “would have overwhelmed the methanotrophs capable of handling the small Gulf spill.” But Retallack can’t find enough methane clathrates in the ocean to account for such a large plume. He still thinks that methane was still involved in the Permian extinction but now he suspects it came from disturbed coal seams.
Reference: Science
http://dx.doi.org/10.1126/science.1199697http://blogs.discovermagazine.com/notro ... pGXAW2PUqh----------
ABIOGENIC ORIGINSMultiple abiogenic processes have been proposed for the formation and accumulation of oil and gas. The two most commonly cited processes proposed are (1) the degassing of the mantle and the polymerization of low-molecular-weight hydrocarbons and (2) the serpentization of ultramafic rocks combined with a Fischer-Tropsch reaction. Both processes were discussed during this conference as well as some other possible mechanisms.
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Keith and Swan reported an association between the hydrothermal processes that form metallic ore deposits and petroleum occurrences. The authors concluded that this relationship suggests that the petroleum forms as part of a hydrothermal reaction sequence. They noted that these hydrothermal hydrocarbons form at temperatures well above the oil window. Keith and Swan proposed a four-stage process. The first stage is serpentization, which through a series of reactions (e.g., Fischer-Tropsch in the presence of iron-nickel and cobalt catalysts) produces a hydrocarbon-bearing fluid. The second stage is the vertical migration of hydrocarbon-bearing hydrothermal solutions. They suggested that the conduit for this fluid movement is commonly strike-slip faults. The third stage is associated with the hydrothermal diagenesis of reservoirs including the formation of high-temperature (saddle) dolomites. The authors suggested that such fields like Ghawar in Saudi Arabia are possible examples of such hydrothermal deposits. The authors further noted that the dolomitization process itself can be an effective means for creating hydrogen and methane. Keith and Swan stated that several large methane-charged hydrothermal seeps have been identified in transform settings such as Lost City (on the Mid-Atlantic Ridge). The fourth stage is the seepage of these fluids and the formation of metalliferous black shales, either nonuraniferous black shales derived from magnesian dunitic peridotite or uraniferous black shales derived from alkalic spinel lherzolite peridotite. They infer that the black shales are a remnant of hydrocarbon seepage instead of a hydrocarbon source and that the associated hydrocarbon seeps provide an energy and nutrient source that sustains the biosphere. Also, they produced evidence that virtually all oils contain diamondoid compounds, which are temperature and pressure resistant.
Charlou, Donval, Jean-Baptiste, Levache, Fouquet, Foucher, and Cochonat also discussed the abiogenic production of petroleum through serpentization of ultramafic material. The driving mechanism is fluid circulation, represented by hydrothermal vents associated with slow-spreading midocean ridges. To support this model, marine geology cruises that examined the Mid-Atlantic Ridge were reviewed. Charlou et al. noted the presence
of several high hydrogen and methane discharge areas including Rainbow.
Most of this methane was derived through serpentization of ultramafic rocks producing hydrogen, which in turn reacts with CO or CO2 in a Fischer-Tropsch-type reaction to yield hydrocarbons. The methane produced in this manner is isotopically heavy. In addition to methane, the authors reported the presence of a much larger suite of organic compounds, including alkanes, alkenes,alcohols, aldehydes, ketones, esters, and a collection of cyclic hydrocarbons. At the Rainbow location, compounds with at least 29 carbons have been reported.
Charlou et al. proposed that minerals such as pyrite, chalcopyrite, and sphalerite act as catalysts for the formation of these higher molecular weight hydrocarbons. They further noted that the degree of polymerization increases with increasing pressure. It was reported that several experimental studies have produced similar organic materials under hydrothermal conditions. The authors identified several key questions, including where the organic compounds are synthesized within the ultramafic plumbing system and what the best conditions are for the formation of these organic molecules. The authors concluded that additional data obtained on both fluid and rock samples on and off the ridge axis will be required to obtain the answers to these questions.
Szatmari, Da Fonseca, and Miekeley suggested that, in addition to an organic (or biogenic) origin, a second inorganic origin cannot be excluded for some oil accumulations. The authors suggest that several lines of evidence that can be used to support an inorganic origin exist. For example, they suggested that the Schulz-Flory distribution of n-alkanes, where the log of alkane abundance is linearly related to the carbon number observed on a synthetic petroleum formed through Fischer-Tropsch, and a suite of naturally occurring Brazilian oils are both indicators of polymerization (and not a result of thermal cracking). The authors also report that the trace element composition of oils better matches that of chondrites, serpentinized peridotites, and primitive mantle material when compared with oceanic or continental crust, with no correlation observed with seawater. Observed variability in trace element compositions may be a reflection of the mixing of different sources. They further suggested that the relative abundance of saturated and unsaturated aliphatics indicates a high hydrogen partial pressure within the setting in which they formed. Szatmari et al. suggested that this hydrogen formed through hydrothermal serpentinization of peridotites. This hydrogen would, in turn, participate in a Fischer-Tropsch reaction catalyzed by trace elements present in the peridotites to form oil. The authors further reported that deformation and unroofing associated with rifting and continental breakup provide a mechanism for this oil to migrate vertically into shallow traps.
http://geoclasses.tamu.edu/gandg/mancin ... s/Katz.pdf
On the Windhexe: ''An engineer could not have invented this,'' Winsness says. ''As an engineer, you don't try anything that's theoretically impossible.''