Characterization and range of kerogen properties in the Vaca Muerta Formation, Neuquén Basin, Argentina

Craddock, Paul R.; Mossé, Laurent; Bernhardt, Carolina; Ortíz, Alberto; Tomassini, Federico González; Saldungaray, Pablo; Pomerantz, Andrew E.

doi:10.1016/j.orggeochem.2019.01.016

Cited by 15 publications

(17 citation statements)

References 11 publications

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“…Despite these constraints, related to the size and resolution of the tomograms, we note a reasonable agreement with PSDs obtained from N 2 adsorption isotherms for the mesopore range . This explains the general agreement between the S sp computed from the CLDs on our set of tomograms and the literature. ,,,, Therefore, the specific mesopore volumes V meso , corresponding to the cumulated pore (between 2 and 50 nm) volumes per gram of sample, are extracted from the aperture size distributions (Table S2). The mean values of V meso range from 0.083 (VM 0.92) to 0.195 cm 3 /g (VM 1.82) and show an upward trend with thermal maturation (Table ).…”

Section: Resultssupporting

confidence: 74%

“…By knowing the TOC of a source rock sample and applying a procedure to substitute the specific surface area attributed to clay minerals (provided quantitative mineralogy is available), one can compute the organic matter’s S sp from adsorption isotherms of bulk rock samples . In parallel, a sample preparation combining acid demineralization and critical-point drying allows direct measurement of kerogen adsorption isotherms that only need to be corrected for the residual pyrite content. ,, The published values of kerogens’ S sp as a function of thermal maturity for a wide range of type II kerogens show that S sp increases by 1 order of magnitude between immature (∼50 m 2 /g TOC) and overmature kerogens in the dry-gas window (∼500 m 2 /g TOC). ,,,, Table S1 evidences that the S sp value computed from the CLDs on our set of tomograms agree with the literature. Such global information, however, does not provide specific insights into the variations of the organic pore morphology and topology.…”

Section: Resultsmentioning

confidence: 99%

“…Our set of source rock samples therefore covers a significant range of thermal maturation experienced by the Vaca Muerta formation. 25,26 1a) were subjected to a flux of argon in a flat ion milling machine (1060SEM Fischione) for 2 cycles of 30 minutes at 5 kV with an incident angle of 5°, followed by 3 cycles of 30 minutes at 5 kV with an incident angle of 2°. The micro-texture was then imaged by a mosaic of backscattered electron (BSE) micrographs (Figure 1b) in a scanning electron microscope (SEM Crossbeam 540 Zeiss) operating with a 20 kV accelerating voltage.…”

Section: Methodsmentioning

confidence: 99%

“…The projection of the HIs allows for the estimation of an “onset” hydrogen index (HI 0 ) of the source rock formation, which is used to compute the transformation ratio (TR HI ) of the organic matter, evolving here from 71.5 to 97.5% (Table ). Our set of source rock samples therefore covers a significant range of thermal maturation experienced by the Vaca Muerta formation. , …”

Section: Methodsmentioning

confidence: 99%

“…7 Realistic atomistic-scale models of kerogens have We herein combine conventional organic geochemistry with electron tomography on a set of organic-rich source rocks covering a wide span of natural thermal maturity to pinpoint its impact on the structural and topological properties of organic porous networks. The selected set of samples originated from a single source rock formation, namely the Vaca Muerta formation 25,26 (Neuquén Basin, Argentina), to minimize differences in the original kerogen composition. This geological formation is composed of a succession of shales and marls and is widely recognized as a prolific hydrocarbon producing resource.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale Accessible Porosity as a Key Parameter Depicting the Topological Evolution of Organic Porous Networks

et al. 2021

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A significant part of the hydrocarbons contained in source rocks remains confined within the organic matter -called kerogen -from where they are generated. Understanding the sorption and transport properties of confined hydrocarbons within the kerogens is, therefore, paramount to predict production. Specifically, knowing the impact of thermal maturation on the evolution of the organic porous network is key. Here, we propose an experimental procedure to study the interplay between the chemical evolution and the structural properties of the organic porous network at the nanometer scale. First, the organic porous networks of source rock samples, covering a significant range of natural thermal maturation experienced by the Vaca Muerta formation (Neuquén basin, Argentina), are physically reconstructed using bright field electron tomography. Their structural description allows us to measure crucial parameters such as the porosity, specific pore volume and surface area, aperture and cavity size distributions, and constriction. In addition, a model-free computation of the topological properties (effective porosity, connectivity, and tortuosity) is conducted. Overall, we document a general increase of the specific pore volume with thermal maturation. This controls the topological features depicting increasing accessibility to alkane molecules, sensed by the evolution of the effective porosity. Collectively, our results highlight the input of bright field electron tomography in the study of complex disordered amorphous porous media, especially to describe the interplay between structural features and transport properties of confined fluids. recently been proposed 8,9 as a means to simulate the nano-structural arrangement of the carbon skeletons and their atoms hybridization at different thermal maturation. The nanoporous networks hence modelized, were evidenced to be responsible for the significant adsorption of hydrocarbons 10,11 , the breakdown of continuum hydrodynamics 10 , the occurrence of selfdiffusion governed transport regimes [12][13][14] , and the presence of interfacial wetting effects. 15 These results contributed greatly to the physical understanding of the fast productivity decline of hydrocarbon production wells of source rocks formations. 2,4,5 Such studies, however, only accounted for nanoscale structural pores (diameter ∅ < 2 nm) of the carbon skeleton, which only constitute the lower bound of the pore size distributions described in the literature.Considering the different sizes of pores making up organic porous networks, as experimentally probed in scanning electron microscopy [16][17][18] , small-angle X-ray and neutron scattering [19][20][21][22] , and gas adsorption 21,23,24 , is paramount to cover the mechanisms affecting hydrocarbon production from source rocks.From an experimental perspective, the analysis of gas adsorption isotherms demonstrated that the thermal maturity of the organic matter affects the pore volume and specific surface area. 21,23,24 Analyses of gas adsorption measurements also...

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