The Open Geology Journal




(Discontinued)

ISSN: 1874-2629 ― Volume 9, 2015

Microbial Processes and Natural Gas Accumulations


The Open Geology Journal, 2011, 5: 75-83

Barry Jay Katz

Chevron Energy Technology Company, 1500 Louisiana Street, Houston, TX 77002, USA.

Electronic publication date 30/12/2011
[DOI: 10.2174/1874262901105010075]




Abstract:

Microbial processes are responsible for the formation, alteration, and destruction of some natural gas accumulations. Individual microbial gas accumulations may be significant (> 1 Tcf; trillion cubic feet or 28.3 billion cubic meters) and collectively account for more than 20% of the global gas resource-base, dominating in some individual basins. Often cited resource estimates do not effectively account for the contribution of microbial gas to mixed biogenicthermogenic gases nor do these estimates fully account for secondary microbial gas.

Microbial gas accumulations form through multiple stages, initiating with the breakdown of large macromolecules into smaller components that the methanogens can effectively utilize as an energy source. There are two primary methanogenic pathways, acetate fermentation and CO2 reduction, both of which may utilize sedimentary organic matter or preexisting oil accumulations as a source.

Microbial gas is typically considered dry (i.e., depleted in C2+ components), but there is clear evidence that ethane and possibly propane may also form through microbial processes.

Numerous authors have provided guidance on the conditions that favor primary microbial gas formation and accumulation including: an anoxic setting, high rates of sedimentation, formation of early traps, low temperatures, favorable migration history, and limited availability of sulfate. Scenarios conducive with secondary microbial gas accumulations have also been discussed. These include the presence of a significant oil pool that can be biodegraded or a coal or organic-rich shale that has achieved thermal maturity levels approaching or beyond the top of the oil-window, which have been uplifted, fractured, and invaded by meteoric water to reintroduce a microbial population.

Gas accumulations may also be biodegraded. Biodegradation results in the preferential removal of C3-5 n-alkanes, leaving isotopically heavier residuals. Ethane is relatively resistant to biodegradation compared to the C3+ homologues. At more advanced levels of biodegradation, the wet gas components are removed yielding a dry gas. As with the biodegradation of oil, the biodegradation of a gas accumulation results in a reduction of the resource-base. The molecular and isotopic compositional changes induced by bacterial alteration of gas accumulations can often complicate their interpretation suggesting more advanced levels of thermal maturity.


Download PDF
Track Your Manuscript:


Endorsements



"Open access will revolutionize 21st century knowledge work and accelerate the diffusion of ideas and evidence that support just in time learning and the evolution of thinking in a number of disciplines."


Daniel Pesut
(Indiana University School of Nursing, USA)

"It is important that students and researchers from all over the world can have easy access to relevant, high-standard and timely scientific information. This is exactly what Open Access Journals provide and this is the reason why I support this endeavor."


Jacques Descotes
(Centre Antipoison-Centre de Pharmacovigilance, France)

"Publishing research articles is the key for future scientific progress. Open Access publishing is therefore of utmost importance for wider dissemination of information, and will help serving the best interest of the scientific community."


Patrice Talaga
(UCB S.A., Belgium)

"Open access journals are a novel concept in the medical literature. They offer accessible information to a wide variety of individuals, including physicians, medical students, clinical investigators, and the general public. They are an outstanding source of medical and scientific information."


Jeffrey M. Weinberg
(St. Luke's-Roosevelt Hospital Center, USA)

"Open access journals are extremely useful for graduate students, investigators and all other interested persons to read important scientific articles and subscribe scientific journals. Indeed, the research articles span a wide range of area and of high quality. This is specially a must for researchers belonging to institutions with limited library facility and funding to subscribe scientific journals."


Debomoy K. Lahiri
(Indiana University School of Medicine, USA)

"Open access journals represent a major break-through in publishing. They provide easy access to the latest research on a wide variety of issues. Relevant and timely articles are made available in a fraction of the time taken by more conventional publishers. Articles are of uniformly high quality and written by the world's leading authorities."


Robert Looney
(Naval Postgraduate School, USA)

"Open access journals have transformed the way scientific data is published and disseminated: particularly, whilst ensuring a high quality standard and transparency in the editorial process, they have increased the access to the scientific literature by those researchers that have limited library support or that are working on small budgets."


Richard Reithinger
(Westat, USA)

"Not only do open access journals greatly improve the access to high quality information for scientists in the developing world, it also provides extra exposure for our papers."


J. Ferwerda
(University of Oxford, UK)

"Open Access 'Chemistry' Journals allow the dissemination of knowledge at your finger tips without paying for the scientific content."


Sean L. Kitson
(Almac Sciences, Northern Ireland)

"In principle, all scientific journals should have open access, as should be science itself. Open access journals are very helpful for students, researchers and the general public including people from institutions which do not have library or cannot afford to subscribe scientific journals. The articles are high standard and cover a wide area."


Hubert Wolterbeek
(Delft University of Technology, The Netherlands)

"The widest possible diffusion of information is critical for the advancement of science. In this perspective, open access journals are instrumental in fostering researches and achievements."


Alessandro Laviano
(Sapienza - University of Rome, Italy)

"Open access journals are very useful for all scientists as they can have quick information in the different fields of science."


Philippe Hernigou
(Paris University, France)

"There are many scientists who can not afford the rather expensive subscriptions to scientific journals. Open access journals offer a good alternative for free access to good quality scientific information."


Fidel Toldrá
(Instituto de Agroquimica y Tecnologia de Alimentos, Spain)

"Open access journals have become a fundamental tool for students, researchers, patients and the general public. Many people from institutions which do not have library or cannot afford to subscribe scientific journals benefit of them on a daily basis. The articles are among the best and cover most scientific areas."


M. Bendandi
(University Clinic of Navarre, Spain)

"These journals provide researchers with a platform for rapid, open access scientific communication. The articles are of high quality and broad scope."


Peter Chiba
(University of Vienna, Austria)

"Open access journals are probably one of the most important contributions to promote and diffuse science worldwide."


Jaime Sampaio
(University of Trás-os-Montes e Alto Douro, Portugal)

"Open access journals make up a new and rather revolutionary way to scientific publication. This option opens several quite interesting possibilities to disseminate openly and freely new knowledge and even to facilitate interpersonal communication among scientists."


Eduardo A. Castro
(INIFTA, Argentina)

"Open access journals are freely available online throughout the world, for you to read, download, copy, distribute, and use. The articles published in the open access journals are high quality and cover a wide range of fields."


Kenji Hashimoto
(Chiba University, Japan)

"Open Access journals offer an innovative and efficient way of publication for academics and professionals in a wide range of disciplines. The papers published are of high quality after rigorous peer review and they are Indexed in: major international databases. I read Open Access journals to keep abreast of the recent development in my field of study."


Daniel Shek
(Chinese University of Hong Kong, Hong Kong)

"It is a modern trend for publishers to establish open access journals. Researchers, faculty members, and students will be greatly benefited by the new journals of Bentham Science Publishers Ltd. in this category."


Jih Ru Hwu
(National Central University, Taiwan)

Browse Contents



Webmaster Contact: info@benthamopen.net
Copyright © 2023 Bentham Open