Divisions Report - DEG

Our Environmental Role in Global Natural Gas

Just before Christmas I was preparing for a presentation to be given to a group of university administrators and corporate and government liaisons on the future of global energy.

I really enjoy the opportunity to discuss broad global topics because, as a geologist, I get to arm-wave a lot!

However, as I review global energy data, it constantly and increasingly impresses on me the long-term future of fossil energy and most importantly, the role of “unconventional” natural gas.

We could discuss the definition of the term “unconventional” and what it really means, but that is best left for another time. What’s more important now is to discuss the role of our environmental efforts to best support the global gas phenomenon.

I believe there are three main environmental issues that we must consider in the utilization of natural gas as a primary fuel source for the next several decades.

The first is the use of water in natural gas production. This includes not only stimulation water but also produced waters, water needed for well site reclamation, water for power production and impacts to human consumption, industrial and agricultural needs.

For clean and efficient natural gas production, we must consider the entire hydrogeologic cycle as well as water surpluses and deficits for the minimum overall environmental impact.

We even can use our geoscience skills to make many current water conditions better, more geologically natural and all within the natural gas production cycle.

Secondly, and many might now argue as most importantly, is the impact of natural gas as it is released into the atmosphere.

Studies provide various values of methane (as well as ethane, propane, and butane, for example) released as free gas from hydraulic fracturing and well site operations and cite the implications. As geologists supporting the clean utilization of natural gas, we must also be aware of these issues and address them from our perspective.

How we address them might be circumstance-dependent – but we have to be knowledgeable and conversant, as well as aware of the best practices to minimize releases.

Finally, we must be aware of the direct day-to-day impact and perspective of natural gas production on the human quality of life – pipelines everywhere, big muddy drill pads, pastoral settings disturbed, viewscapes obliterated, ugly “big oil” taking over the family farm. We all have heard these objections.

Although there has been a certain amount of historical truth supporting these perceptions, we can help by reminding people that most energy companies practice responsible environmental programs with publically available environmental policies.

Maybe the best way to help the public understand is by showing them what we do as environmentally aware geoscientists, that we also expect and demand responsible environmental programs associated with natural gas production and utilization, and that we too appreciate clean fields, hiking trails and natural viewscapes. It is who we are!

I recently reviewed data that strongly suggested:

  • Our estimates of gas in place are grossly underestimated.
  • The volume of potential source rocks is also considerably underestimated.

Wow!

The future of natural gas is strong, and so is our AAPG-DEG need to ensure that these resources are utilized in a safe, clean, efficient and effective environmental way.

(BTW, I have recently changed jobs. If you wish to communicate please email me at douglas.wyatt@halliburton.com.)

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Division Column-DEG Doug Wyatt

Doug Wyatt, of Aiken, S.C., is director of science research for the URS Corporation Research and Engineering Services contract to the USDOE National Energy Technology Laboratory. He also is a member of the DEG Advisory Board for the AAPG Eastern Section.

Division Column DEG

The Division of Environmental Geosciences (DEG), a division of AAPG, is concerned with increasing awareness of the environment and the petroleum industry and providing AAPG with a scientific voice in the public arena. Among its objectives are educating members about important environmental issues, supporting and encouraging research on the effects of exploration and production on the environment, and communicating scientific information to concerned governmental agencies.

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See Also: Bulletin Article

Size fractions (<4 and 0.4–1.0 μ) of Brent Group sandstones from the northern North Sea contain mostly illite-smectite mixed layers with kaolinite, whereas the same size fractions of Fulmar Formation sandstones from the south-central North Sea consist of illite-smectite mixed layers with minor chlorite. Transmission electron microscope observations show elongated illite laths or agglomerates consisting of small laths when larger individual laths are lacking.

The K-Ar data of the fractions less than 0.4 μm of Brent Group samples plot on two arrays in a 40Ar/36Ar vs. 40K/36Ar diagram that have isochron characteristics with ages of 76.5 ± 4.2 and 40.0 ± 1.5 Ma, and initial 40Ar/36Ar ratios of 253 ± 16 and 301 ± 18, respectively. For the Fulmar Formation samples, the data points of the fractions less than 0.2 and less than 0.4 μ also fit two isochrons with ages of 76.6 ± 1.4 and 47.9 ± 0.5 Ma and initial 40Ar/36Ar ratios of 359 ± 52 and 304 ± 2, respectively. Some of the coarser 0.4–1.0-μ fractions also plot on the two isochrons, but most plot above indicating the presence of detrital components more than 0.4 μ. The almost identical ages obtained from illite-type crystals of sandstones with different deposition ages that are located about 600 km (373 mi) apart record two simultaneous illitization episodes. These events were not induced by local burial conditions, but are related to episodic pressure and/or temperature increases in the studied reservoirs, probably induced by hydrocarbon injection. This interpretation is indirectly supported by notably different K-Ar illite ages from cores of a nearby reservoir at hydrostatic pressure.

Illite is not as well crystallized as expected for potential crystallization temperatures above 160°C measured by fluid-inclusion determinations. In both the northern and south-central North Sea, the two illite generations remain unaffected after crystallization despite continued burial, suggesting notably higher crystallization temperatures than those estimated from geothermal gradients. No recent illite crystallization or alteration is recorded in the K-Ar ages, despite a dramatic regional acceleration of the subsidence in the southern North Sea. ±

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See Also: CD DVD

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See Also: Field Seminar

The seminar focuses on the lithologic variations that characterize clastic reservoir facies and on development of models that can be used to predict these variations in the subsurface.

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