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Mineralogy of Shale Gas and Other Low Permeability Reservoirs

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (20 March 2020) | Viewed by 34168

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Dr. Gareth Chalmers

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School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia
Interests: mineralogy; sedimentary processes; diagenesis; electron microscopy; geochemistry; permeability; pore development; unconventional petroleum resources; sustainability; environmental mineralogy; contaminated sediments
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Dear Colleagues,

Shale gas reservoirs and other low permeability rocks have become significant contributors to global hydrocarbon production in the past two decades, with shale gas contributing up to 30% of the world’s natural gas supply by 2040. Shale gas production is complex because of the combination of geological processes that control the reservoir characteristics. These processes include primary depositional environment, diagenetic processes (mineral and organic), and structural processes. The mineralogy of shale gas reservoirs and other tight reservoirs is an important characteristic that governs whether a shale play will be successfully developed, as the mineral composition controls, in part, the pore system that dictates the hydrocarbon density and natural permeability of these rocks. The mineralogy has significant influence on the geomechanical properties of the reservoirs, and the ability for these rocks to be fractured to increase permeability to economic rates. Mineral composition and texture also have a large impact on the geochemistry of the produced fluids, as hydraulic fracture fluids interact with the reservoir’s minerals and pore fluids. The impact mineralogy has on produced water geochemistry has large implications on water treatment, recycling, and social license to develop these resources.

This Special Issue aims to publish papers that explore the role that primary and secondary minerals in low permeability reservoirs (shale, mudstones, siltstone, and tight sandstones) have on the development of the porosity, permeability, and geomechanics. Research that investigates the influence that the mineral composition and texture have on the geochemistry of produced water are also welcome.

Dr. Gareth Chalmers
Guest Editor

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Keywords

mineral composition
diagenetic processes
depositional environments
geomechanics
fracture stimulation
porosity
permeability
rock–fluid interactions
geochemistry

Published Papers (9 papers)

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Research

25 pages, 13037 KiB

Open AccessArticle

Significance and Distribution of Apatite in the Triassic Doig Phosphate Zone, Western Canada Sedimentary Basin

by Pablo Lacerda Silva and R. Marc Bustin

Minerals 2020, 10(10), 904; https://doi.org/10.3390/min10100904 - 12 Oct 2020

Cited by 3 | Viewed by 2721

Abstract

The Doig Phosphate Zone (DPZ) is a phosphate-bearing marine unit located at the base of the Doig Formation, in the Triassic section of the Western Canada Sedimentary Basin. The DPZ has a maximum thickness of 90 m and extends across northeastern British Columbia and west-central Alberta. In this study, we characterize the significance and interpret the origin of apatite in the DPZ through mineralogical and geochemical analyses, thin section study, and field emission scanning electron microscopy. The occurrence of apatite in the DPZ is not evenly distributed but restricted to discrete 10 to 20 cm thick beds, located near the base of the DPZ. Phosphorites are of two types: grainstones composed primarily of unconformity-bounded coated grains, and intraclastic phosphorites composed of detrital silt-sized grains and apatite coated grains in a cryptocrystalline phosphatic matrix. The phosphorite beds are records of stratigraphic condensation due to low detrital input during transgression. The erosionally truncated phosphatic coated grains and intraclasts are interpreted to be a result of various phases of phosphatization, exhumation, erosion, reworking, winnowing, and redeposition in alternating quiescence and storms or bottom currents. The abundance of pyrite and chalcophile trace elements, as well as the low concentration of proxy elements for organic matter productivity and preservation, are further evidence of stratigraphic condensation, with sulfidic pore water development and extensive organic recycling promoted by biological activity during the long exposure times. The phosphorites were formed under oxygenated water conditions, as suggested by the depletion in Ce and the presence of a diverse benthic fauna. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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33 pages, 13430 KiB

Open AccessArticle

Impact of Diagenesis on the Reservoir Properties of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa

by Temitope Love Baiyegunhi, Kuiwu Liu, Oswald Gwavava and Christopher Baiyegunhi

Minerals 2020, 10(9), 757; https://doi.org/10.3390/min10090757 - 27 Aug 2020

Cited by 8 | Viewed by 2659

Abstract

The Cretaceous sandstone in the Bredasdorp Basin is an essential potential hydrocarbon reservoir. In spite of its importance as a reservoir, the impact of diagenesis on the reservoir quality of the sandstones is almost unknown. This study is undertaken to investigate the impact of digenesis on reservoir quality as it pertains to oil and gas production in the basin. The diagenetic characterization of the reservoir is based on XRF, XRD SEM + EDX, and petrographic studies of 106 thin sections of sandstones from exploration wells E-AH1, E-AJ1, E-BA1, E-BB1 and E-D3 in the basin. The main diagenetic processes that have affected the reservoir quality of the sandstones are cementation by authigenic clay, carbonate and silica, growth of authigenic glauconite, dissolution of minerals and load compaction. Based on the framework grain–cement relationships, precipitation of the early calcite cement was either accompanied or followed up by the development of partial pore-lining and pore-filling clay cements, particularly illite. This clay acts as pore choking cement, which reduces porosity and permeability of the reservoir rocks. The scattered plots of porosity and permeability versus cement + clays show good inverse correlations, suggesting that the reservoir quality is mainly controlled by cementation and authigenic clays. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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17 pages, 6494 KiB

Open AccessArticle

Quantitative Prediction of Fractures in Shale Using the Lithology Combination Index

by Zhengchen Zhang, Pingping Li, Yujie Yuan, Kouqi Liu, Jingyu Hao and Huayao Zou

Minerals 2020, 10(6), 569; https://doi.org/10.3390/min10060569 - 25 Jun 2020

Cited by 4 | Viewed by 2424

Abstract

Fractures, which are related to tectonic activity and lithology, have a significant impact on the storage and production of oil and gas in shales. To analyze the impact of lithological factors on fracture development in shales, we selected the shale formation from the Da’anzhai member of the lower Jurassic shales in a weak tectonic deformation zone in the Sichuan Basin. We defined a lithology combination index (LCI), that is, an attribute quantity value of some length artificially defined by exploring the lithology combination. LCI contains information on shale content at a certain depth, the number of layers in a fixed length (lithology window), and the shale content in the lithology window. Fracture porosity is the percentage of pore volume to the apparent volume of the rock. In the experiment, fracture porosity was obtained using 50 samples from six wells, by observing rock slices under a microscope. The relationship between LCI and fracture porosity was analyzed based on machine learning, regression analysis, and weighting methods. The results show that LCI is able to represent the impact of multiple lithological factors (i.e., shale content at a certain depth, the number of layers in the lithology window, and the shale content in the lithology window). The LCI within a thickness of 2 m for the lithology window demonstrates a good linear relationship with fracture porosity. We therefore suggest LCI be used for fracture predictions of shale formations from weak tectonic deformation zones. Our proposed LCI and fracture prediction methods also provide implications for sandstone, mudstone, or carbonate formations under similar processes. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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21 pages, 12442 KiB

Open AccessArticle

Nano-Scale Pore Structure and Its Multi-Fractal Characteristics of Tight Sandstone by N₂ Adsorption/Desorption Analyses: A Case Study of Shihezi Formation from the Sulige Gas Filed, Ordos Basin, China

by Zhelin Wang, Xuewei Jiang, Mao Pan and Yongmin Shi

Minerals 2020, 10(4), 377; https://doi.org/10.3390/min10040377 - 22 Apr 2020

Cited by 53 | Viewed by 6556

Abstract

Fractal dimension is a critical parameter to evaluate the heterogeneity of complex pore structure in tight sandstone gas and other low permeability reservoirs. To quantify the fractal dimension of tight sandstone at various pore size classes and evaluate their implications on mineral composition and nano pore structure parameters, we conducted an integrated approach of N₂ adsorption/desorption experiment (N₂-GA), X-ray diffraction (X-RD), and field emission scanning electron microscopy (FE-SEM) on Sulige tight sandstone reservoirs. By comparing the nine types of fractal dimensions calculated from N₂ adsorption data, we put forward the concept of “concentrated” fractal dimensions and “scattered” fractal dimensions (D_N2, D_N3, D_N5, D_N7 and D_N8) for the first time according to its concentration extent of distribute in different samples. Result shows that mineral composition has a significant influence of a different level on specific surface area (SSA), pore volume (PV), and fractal dimensions (D_N), respectively, where the “scattered” fractal dimension is more sensitive to certain specific property of the reservoir, including mineral content and the specific surface area contribution rate (S_r) of type II mesopores (Mesopore-II: 10~50nm). In addition, three type of hysteresis loops were distinguished corresponding to different pore shape combination of N₂-GA isotherm curve, which reveals that pore structure heterogeneity is mainly controlled by inkbottle-shaped pores and the volume contribution rate (V_r) of mesopores in this study area. These findings could contribute to a better understanding of the controlling effect of pore heterogeneity on natural gas storage and adsorption. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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16 pages, 5915 KiB

Open AccessArticle

Effect of Mineral Composition on Transverse Relaxation Time Distributions and MR Imaging of Tight Rocks from Offshore Ireland

by Stian Almenningen, Srikumar Roy, Arif Hussain, John Georg Seland and Geir Ersland

Minerals 2020, 10(3), 232; https://doi.org/10.3390/min10030232 - 03 Mar 2020

Cited by 7 | Viewed by 2843

Abstract

In this paper, we investigate the effect of magnetic field strength on the transverse relaxation time constant (T₂) in six distinct core plugs from four different rock types (three sandstones, one basalt, one volcanic tuff and one siltstone), retrieved from offshore Ireland. The CPMG pulse-sequence was used at two different magnetic field strengths: high-field at 4.70 T and low-field at 0.28 T. Axial images of the core plugs were also acquired with the RAREst sequence at high magnetic field strength. Thin-sections of the core plugs were prepared for optical imaging and SEM analysis, and provided qualitative information on the porosity and quantification of the elemental composition of the rock material. The content of iron varied from 4 wt. % to close to zero in the rock samples. Nevertheless, the effective T₂ distributions obtained at low-field were used to successfully predict the porosity of the core plugs. Severe signal attenuations from internal magnetic gradients resulted in an underestimation of the porosity at high-field. No definitive trend was identified on the evolution of discrete relaxation time components between magnetic field strengths. The low-field measurements demonstrate that NMR is a powerful quantitative tool for petrophysical rock analysis as compared to thin-section analysis. The results of this study are of interest to the research community who characterizes natural gas hydrates in tight heterogeneous core plugs, and who typically relies on MR imaging to distinguish between solid hydrates and fluid phases. It further exemplifies the importance of selecting appropriate magnetic field strengths when employing NMR/MRI for porosity calculation in tight rock. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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14 pages, 3413 KiB

Open AccessArticle

Synthesis, Property and Mechanism Analysis of a Novel Polyhydroxy Organic Amine Shale Hydration Inhibitor

by Weichao Du, Xiangyun Wang, Gang Chen, Jie Zhang and Michal Slaný

Minerals 2020, 10(2), 128; https://doi.org/10.3390/min10020128 - 31 Jan 2020

Cited by 55 | Viewed by 4213

Abstract

Based on the adsorption mechanism analysis of polyhydroxy organic compound on a shale surface, a novel polyhydroxy organic amine shale hydration inhibitor N, N, N′, N′-tetrakis (2-hydroxyethyl) ethylenediamine (THEED) was synthesized via a nucleophilic reaction by using diethanolamine and dibromoethane as raw materials. Its structure was characterized by Fourier transform infrared spectrometry (FTIR), Hydrogen Nuclear Magnetic Resonance (¹H NMR) and Liquid Chromatography Mass Spectrometry (LCMS). The inhibition performance of THEED was studied by a shale rolling recovery experiment, a linear expansion experiment and the particle size distribution experiment. Results showed the shale rolling recovery rate in 2.0 wt % THEED solutions was up to 89.6% at the rolling condition of 100 °C × 16 h, and the linear expansion height of artificial shale core in 2.0 wt % THEED solutions was just 4.74 mm after 16 h. The average particle size of Na-bentonite (Na-MMT) in fresh water was 8.05 μm, and it was observed that the average particle size has been increased to 124 μm in 2.0 wt % THEED solutions. The shale hydration inhibition mechanism of the novel inhibitor THEED was analyzed by FTIR, Scanning Electron Microscopy (SEM) and X-ray diffractometry (XRD), we concluded that the nice shale hydration inhibition performance of THEED was achieved by means of intercalation and adsorption onto the surface of shale. The superior shale hydration inhibition property makes THEED promising in maintaining wellbore stability in drilling engineering. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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22 pages, 7211 KiB

Open AccessArticle

The Albitization of K-Feldspar in Organic- and Silt-Rich Fine-Grained Rocks of the Lower Cambrian Qiongzhusi Formation in the Southwestern Upper Yangtze Region, China

by Huajun Min, Tingshan Zhang, Yong Li, Shaoze Zhao, Jilin Li, Dan Lin and Jincheng Wang

Minerals 2019, 9(10), 620; https://doi.org/10.3390/min9100620 - 08 Oct 2019

Cited by 10 | Viewed by 5336

Abstract

The albitization of K-feldspar is a common diagenetic process that has thus far received little attention and is not fully understood in fine-grained sedimentary rocks. To better understand the albitization of K-feldspar, studies in organic- and silt-rich fine-grained rocks of the lower Cambrian Qiongzhusi Formation in the southwestern Upper Yangtze region, China, were carried out via X-ray diffractometry (XRD) and field emission scanning electron microscopy (FE-SEM). The results show that five types of albitized K-feldspar textures have developed: microcrystal albite replacement, irregular blocky replacement along margins, cleavage planes or microcracks of K-feldspars, complete pseudomorphic replacement, albite overgrowth, and albite pore filling. Organic- and silt-rich fine-grained rocks differ from sandstones and mudstones in terms of the rock structure and mineral assemblage, which results in differences in the textures and degree of albitization of K-feldspar. Illitization of clay has an impact on the albitization of K-feldspar. In provenance analyses using feldspar, fine-grained rocks, especially those that underwent mesogenesis, should be treated with caution because detrital feldspars have been destroyed. Theoretically, the albitization of K-feldspar could increase the porosity of reservoirs, although, from our observations, most of the related secondary pores are cancelled out or became isolated pores due to other diagenetic processes (compaction, cementation, etc.) in organic- and silt-rich fine-grained rocks. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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26 pages, 6940 KiB

Open AccessArticle

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

by Xingmeng Wang, Zhenxue Jiang, Shu Jiang, Jiaqi Chang, Lin Zhu, Xiaohui Li and Jitong Li

Minerals 2019, 9(9), 543; https://doi.org/10.3390/min9090543 - 09 Sep 2019

Cited by 41 | Viewed by 3670

Abstract

Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion porosimetry (HMIP), and low-pressure N₂/CO₂ adsorption were used to qualitatively and quantitatively characterize full-scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro-, meso- and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D₁ and D₂ which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N₂ desorption data. The value of D₁ is in the range of 2.6480–2.7334 (average of 2.6857), D₂ is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D₁ and D₂. The fractal dimension D₁ decreases with increasing average pore diameter, while D₂ is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D₁, and positive influence D₂, while brittle minerals show an opposite effect compared with clay minerals. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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15 pages, 14549 KiB

Open AccessArticle

The Early Silurian Sedimentary Environment of Middle-Upper Yangtze: Lithological and Palaeontological Evidence and Impact on Shale Gas Reservoir

by Xiaorong Qu, Yanming Zhu, Yang Wang and Fuhua Shang

Minerals 2019, 9(8), 494; https://doi.org/10.3390/min9080494 - 18 Aug 2019

Cited by 3 | Viewed by 2801

Abstract

The organic-enriched thick shale at the bottom of Longmaxi Formation is laterally continuous distributed and has been proven to be of good production capability in Fuling of Upper Yangtze. Uplifts that developed during the sedimentation influenced the reservoir characteristics by taking control of the sedimentary environment and provenance. The sedimentary environments are mainly deep-water shelf, shallow-water shelf, and tidal flat. By analyzing reservoir characteristic of these three environments, the deep-water shelf, which dominated the early stage of sedimentation, formed a high-quality reservoir with high TOC (Total Organic Carbon) content, porosity, and brittleness, while the environment was maintained around the basin centre until the Early Silurian. The shales deposited under the shallow-water environment were of low porosity because of the increasing calcareous and argillaceous contents. Sediments which formed on the tidal flat were arenaceous and of the lowest TOC content as the organic preservation conditions deteriorated. The good correlation of graptolite abundance and TOC content, and high porosity within graptolite fossils emphasize the importance of palaeontological development. The argillaceous cap over the Longmaxi shale is of good sealing capability, and the continuous sedimentation zone along southern Sichuan–eastern Chongqing is the best optimized hydrocarbon-bearing system. However, a weak interface on the discontinuity is the potential lateral pathway for gas diffusion at Northern Guizhou and Western Hunan, but on the southeast margin where the dark shale and the tidal sandstone contact, it promises to form a tight gas reservoir. Full article

(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)

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