Shale lithofacies controls on porosity and pore structure: An example from Ordovician Goldwyer Formation, Canning Basin, Western Australia

Iqbal, Muhammad Atif; Rezaee, Reza; Smith, Gregory; Ekundayo, Jamiu M.

doi:10.1016/j.jngse.2021.103888

“…Researchers have concluded that the pore structure of organic-rich shale is generally governed by diagenesis, organic matter, mineral components, thermal maturity, kerogen type, etc., depending on specific geological conditions [14,23,[53][54][55][56][57]. Shale lithofacies have important controls on porosity and pore structure due to different sedimentary environments and mineralogical variations [19,51,[58][59][60][61]. The same scenario can also be observed in our study.…”

Section: Discussionsupporting

confidence: 77%

Paleoenvironment, Geochemistry, and Pore Characteristics of the Postmature to Overmature Organic-Rich Devonian Shales in Guizhong Depression, Southwestern China

Zhang

¹

,

Liu

²

,

Changxi

³

et al. 2021

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Investigating shale pore characteristics has deepened our understanding of shale reservoir, while that of postmature-overmature shales is yet to be revealed, which is especially critical for shale gas evaluation in southern China. Ten Middle-Upper Devonian organic-rich shale samples were collected from well GY-1 in the Guizhong Depression, and the paleoenvironment, geochemistry, and pore system were analyzed with a series of experiments, including trace element analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), low-pressure N2 adsorption, and source rock geochemistry. Results show that the Middle-Upper Devonian shales in the Guizhong Depression are organic-rich mudstones with TOC ranging from 0.14% to 6.21%, which is highest in the Nabiao Formation ( D 2 n ) and Lower Luofu Formation ( D 2 l ) that were deposited in the anoxic and weak hydrodynamic deep-water shelf. They are thermally postmature to overmature with equivalent vitrinite reflectance ( EqV R o ) of 3.40%~3.76% and type I kerogen. The lithofacies in D 2 n and D 2 l are primarily siliceous/argillaceous mixed shale as well as a few siliceous argillaceous shales and argillaceous siliceous shales as well. Organic matter- (OM-) hosted pores within bitumen are primary storage volume, rather than inorganic pores (interparticle and intraparticle) which are rare. The total helium porosity of samples varies between 1.20% and 4.49%, while total surface area and pore volume are 2.39-14.22 m2/g and 0.0036-0.0171 ml/g, respectively. Porosity, pore surface area, and pore volume are in accordance with increasing TOC, R o , and siliceous mineral contents. Considerable OM-macropores are found in shales with R o > 3.6 % in our study which demonstrates that the porosity at postmature to overmature stage ( R o = 3.5 − 4.0 % ) does not change fundamentally. The high level of maturity is not considered the main controlling factor that affects shale gas content, and more attention should be paid to preservation conditions in this area.

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“…The black colour and promising TOCs (>0.5 wt.%) of the carbonaceous mudstone lithofacies indirectly indicate deposition in reducing conditions, which enhances OM preservation (Jalees & Fazeelat, 2020). The lithofacies having organic richness (TOC 0.5–4 wt.%) are considered promising intervals for shale‐gas generation and reservoir quality (Iqbal et al, 2021; Jarvie, 2012). High TOC contents provide more organic pores and gas holding capacity within shale‐gas reservoirs as OM is more porous compared to solid minerals (Chen et al, 2019; Shu et al, 2021; Zhang et al, 2020).…”

Section: Resultsmentioning

confidence: 99%

“…Global energy transition and conventional hydrocarbon resource depletion have led to increased interests in worldwide unconventional shale‐gas investigation and exploration owing to its long‐term potential and economic viability (Iqbal, Rezaee, Smith, & Ekundayo, 2021; Jadoon et al, 2017; Milkov, Faiz, & Etiope, 2020). Recently, the successful production of hydrocarbons from unconventional shale‐gas reservoirs in North America and Canada have brought a paradigm shift in the world energy landscape and initiated a number of detailed studies on these resources throughout the world (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the successful production of hydrocarbons from unconventional shale‐gas reservoirs in North America and Canada have brought a paradigm shift in the world energy landscape and initiated a number of detailed studies on these resources throughout the world (e.g. Chen et al, 2019; Iqbal et al, 2021; Jarvie, 2012; Kerschke & Schulz, 2015; Wang et al, 2020). Shale‐gas exploration and development in drilling technology enabled the United States to produce approximately 50% of its natural gas from shale‐gas reservoirs, and the trend is increasing in other parts of the world (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, it has been anticipated that lithofacies characterization has a significant role in determining shale‐gas reservoir quality and performance. For instance, mineral composition, OM types and pore network development are largely constrained by lithofacies types (Iqbal et al, 2021; Kerschke & Schulz, 2015; Zhang et al, 2020). Likewise, a considerable variation in natural gas recoveries from shale‐gas plays have been reported, which is largely because of textural and compositional variations within lithofacies characteristics (Shu, Lu, Hu, Wang, & Wang, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Depositional and diagenetic constraints on the quality of shale‐gas reservoirs: A case study from the Late Palaeocene of the Potwar Basin (Pakistan, Eastern Tethys)

Khan

¹

,

Weltje

²

,

Jan

³

et al. 2022

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Unconventional shale‐gas reservoir assessment concurs numerous exploration challenges, often related to their complex lithology, which reflects secular changes in depositional environment(s) as well as spatially variable diagenetic overprinting. This study combines a range of methods (sedimentological, petrographical, CL‐microscopy, X‐ray diffraction, TOC (total organic carbon), TON (total organic nitrogen) and δ13Corg and δ15Norg stable isotopes) to address the controls of lithofacies, palaeo‐depositional environment(s) and diagenesis on the shale‐gas reservoir potential of the Late Palaeocene Patala Formation in the Potwar Basin of Pakistan. This formation records sediment accumulation in a shallow, mixed siliciclastic‐carbonate shelf environment. Sedimentological and X‐ray diffraction (XRD) analyses show that the formation is primarily composed of an alternation of carbonaceous, siliceous, calcareous and argillaceous mudstone lithofacies. Detrital assemblages, including grains of quartz, apatite, calcite, chlorite, as well as organic matter (OM) and clay minerals with auxiliary (authigenic) pyrite, dominate the formation. High terrigenous influx is represented by the abundance of siliciclastics and terrigenous OM. The δ13Corg and δ15Norg proxies reflect dysoxic to anoxic palaeo‐environmental conditions, which promoted preservation of mixed marine and terrigenous OM, a setting considered to be indicative for high shale‐gas potential. The organic‐rich siliceous and carbonaceous mudstone lithofacies are considered to be the most prospective intervals, while calcareous and argillaceous mudstones are considered least promising in terms of reservoir quality. Spatially variable eo‐, meso‐ and telo‐diagenetic features such as compaction, cementation, stylolitization, dissolution and re‐precipitation are superimposed upon the depositional fabric, which locally affected the reservoir quality of the Patala Formation. The results of this study strongly suggest that the organic‐ and quartz‐rich mudstone lithofacies constitute “sweet spots” whose occurrence in space and time may be traced to design a strategy for shale‐gas exploration in the Potwar Basin of Pakistan and in analogous settings elsewhere.

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Characterizing pore size distribution of high maturity shales and main controlling factors analysis: A case study of Permian Gufeng Formation in the Lower Yangtze region, China

Xu¹,

Gui²,

Wu

³

et al. 2023

Geological Journal

0

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Shale gas resource is heterogeneously distributed in Permian Gufeng Formation in the Xuancheng area, Anhui Province. This research aims to investigate the pore size distribution of the Permian Gufeng shales via 16 core samples analyses, combined with x‐ray diffraction, low‐pressure nitrogen gas adsorption (N2‐GA), CO2 gas adsorption (CO2‐GA) and scanning electron microscopy (SEM). N2‐GA shows that the nanopores (diameter < 10 nm) are dominated and developed in the samples. The Brunauer–Emmett–Teller (BET) specific surface area (SSA) of the samples ranges from 6.7051 to 29.4384 m2/g, with a mean of 16.0931 m2/g. CO2‐GA results illustrate that micropore is well developed, especially the pores with a diameter of 0.5–0.6 and 0.8 nm. The total organic carbon (TOC) content of the Gufeng shale ranges from 0.42% to 12.82% with an average content of 6.44%, which has both positive correlation with pore SSA and pore volume, while carbonate mineral content has a positive correlation with pore SSA and the volume of macropore and mesopore. Clay mineral content is a negative correlation with pore SSA and micropore volume. Therefore, the high‐maturity Permian Gufeng shale could be more preferential high‐quality gas shale reservoir for further exploration and development in the Xuancheng area, which has more than 4% TOC content, relatively higher carbonate mineral content and relatively lower clay mineral content.

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Shale lithofacies controls on porosity and pore structure: An example from Ordovician Goldwyer Formation, Canning Basin, Western Australia

Cited by 32 publications

References 56 publications

Paleoenvironment, Geochemistry, and Pore Characteristics of the Postmature to Overmature Organic-Rich Devonian Shales in Guizhong Depression, Southwestern China

Paleoenvironment, Geochemistry, and Pore Characteristics of the Postmature to Overmature Organic-Rich Devonian Shales in Guizhong Depression, Southwestern China

Depositional and diagenetic constraints on the quality of shale‐gas reservoirs: A case study from the Late Palaeocene of the Potwar Basin (Pakistan, Eastern Tethys)

Characterizing pore size distribution of high maturity shales and main controlling factors analysis: A case study of Permian Gufeng Formation in the Lower Yangtze region, China

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