Dataset Information

Fractal evolution under in situ pressure and sorption conditions for coal and shale.

ABSTRACT: Coalbed methane (CBM) and shale gas become two most important unconventional natural gas resources in US. The fractal dimension, known as the degree of self-similarity or irregularity, is an important parameter to quantitatively characterize gas storage capacity and gas transport properties in pores of rock matrix. In this study, two coal and two shale samples were evaluated to estimate fractal dimensions using combined small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and low-pressure N2 adsorption techniques. The results show that surface fractal dimension D s of inaccessible pores is greater than that for total pores based on SANS results for all four tested samples. D s of accessible pores estimated by N2 desorption is greater than that for N2 adsorption for each linear section of each tested sample. Based on in situ SANS results, D s slightly decreases with increasing argon injecting pressure for San Juan coal. D s decreases with increasing methane and CO2 injecting pressure for samples with high D s . However, D s significantly increases when CO2 became liquid phase for samples with low D s . Furthermore, D s almost didn't change after methane and argon penetrations for all these samples except Marcellus outcrop shale.

SUBMITTER: Zhang R

PROVIDER: S-EPMC5566402 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Fractal evolution under in situ pressure and sorption conditions for coal and shale.

Zhang Rui R Liu Shimin S Wang Yang Y

Scientific reports 20170821 1

Coalbed methane (CBM) and shale gas become two most important unconventional natural gas resources in US. The fractal dimension, known as the degree of self-similarity or irregularity, is an important parameter to quantitatively characterize gas storage capacity and gas transport properties in pores of rock matrix. In this study, two coal and two shale samples were evaluated to estimate fractal dimensions using combined small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) a ...[more]

PMID: 28827654

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Project description:The pelagic realm of the dark ocean is characterized by high hydrostatic pressure, low temperature, high-inorganic nutrients, and low organic carbon concentrations. Measurements of metabolic activities of bathypelagic bacteria are often underestimated due to the technological limitations in recovering samples and maintaining them under in situ environmental conditions. Moreover, most of the pressure-retaining samplers, developed by a number of different labs, able to maintain seawater samples at in situ pressure during recovery have remained at the prototype stage, and therefore not available to the scientific community. In this paper, we will describe a ready-to-use pressure-retaining sampler, which can be adapted to use on a CTD-carousel sampler. As well as being able to recover samples under in situ high pressure (up to 60 MPa) we propose a sample processing in equi-pressure mode. Using a piloted pressure generator, we present how to perform sub-sampling and transfer of samples in equi-pressure mode to obtain replicates and perform hyperbaric experiments safely and efficiently (with <2% pressure variability). As proof of concept, we describe a field application (prokaryotic activity measurements and incubation experiment) with samples collected at 3,000m-depth in the Mediterranean Sea. Sampling, sub-sampling, transfer, and incubations were performed under in situ high pressure conditions and compared to those performed following decompression and incubation at atmospheric pressure. Three successive incubations were made for each condition using direct dissolved-oxygen concentration measurements to determine the incubation times. Subsamples were collected at the end of each incubation to monitor the prokaryotic diversity, using 16S-rDNA/rRNA high-throughput sequencing. Our results demonstrated that oxygen consumption by prokaryotes is always higher under in situ conditions than after decompression and incubation at atmospheric pressure. In addition, over time, the variations in the prokaryotic community composition and structure are seen to be driven by the different experimental conditions. Finally, within samples maintained under in situ high pressure conditions, the active (16S rRNA) prokaryotic community was dominated by sequences affiliated with rare families containing piezophilic isolates, such as Oceanospirillaceae or Colwelliaceae. These results demonstrate the biological importance of maintaining in situ conditions during and after sampling in deep-sea environments.

Dataset Information

Fractal evolution under in situ pressure and sorption conditions for coal and shale.

Publications

Fractal evolution under in situ pressure and sorption conditions for coal and shale.

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