Quantification of clay mineral microporosity and its application to water saturation and effective porosity estimation: A case study from Upper Ordovician reservoir, Libya

Alansari, Abubaker; Salim, Ahmed Mohamad Ahmed; Janjuhah, Hammad Tariq; Rahman, Abdul Hadi Bin Abd; Fello, Nuri Mohamed

doi:10.1016/j.jnggs.2019.04.005

Cited by 10 publications

(3 citation statements)

References 8 publications

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“…The air phase (1) corresponds to the intergranular pores resolvable from the µCT image volume, and the grain phase (2) corresponds to the quartz and feldspar grains. The pore‐filling clay matrix and silica (opal‐CT) cement are estimated to contain 60 to 70% intragranular microporosity, which lies below the µCT image resolution, which is calculated based on mass balance considerations (Callow et al ., 2020) and literature microporosity estimates for smectite clay and silica (opal‐CT) cement (Hurst & Nadeau, 1995; Alansari et al ., 2019).…”

Section: Methodsmentioning

confidence: 99%

Permeability heterogeneity of sandstone intrusion fluid‐escape systems, Panoche Hills, California: Implications for sedimentary basins globally

et al. 2022

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Natural surface gas seeps provide a significant input of greenhouse gas emissions into the Earth's atmosphere and hydrosphere. The gas flux is controlled by the properties of underlying fluid-escape conduits, which are present within sedimentary basins globally. These conduits permit pressuredriven fluid flow, hydraulically connecting deeper strata with the Earth's surface; however they can only be fully resolved at sub-seismic scale. Here, a novel 'minus cement and matrix permeability' method using threedimensional X-ray micro-computed tomography imaging enables the improved petrophysical linkage of outcrop and sub-surface data. The methodology is applied to the largest known outcrop of an inactive fluid-escape system, the Panoche Giant Intrusion Complex in Central California, where samples were collected along transects of the 600 to 800 m stratigraphic depth range to constrain porosity and permeability spatial heterogeneity. The presence of silica cement and clay matrix within the intergranular pores of sand intrusions are the primary control of porosity (17 to 27%) and permeability (≤1 to ca 500 mD) spatial heterogeneity within the outcrop analogue system. Following the digital removal of clay matrix and silica (opal-CT and quartz) cement derived from the mudstone host strata, the sand intrusions have porosityÀpermeability ranges of ca 30 to 40% and 10 3 to 10 4 mD. These calculations are closely comparable to active sub-surface systems in sedimentary basins. Field observations revealed that, at decreasing depth, the connected sand intrusion network reduces in thickness and becomes carbonate cemented, terminating at carbonate mounds formed from methane escape at the seafloor. A new conceptual model integrates the pore-scale calculations and field-scale observations to highlight the key processes that control sand intrusion permeability, spatially and temporally. The study demonstrates the control of matrix and cement addition on the physical properties of fluid-escape conduits, which has significance for hydrocarbon reservoir characterization and modelling, as well as subsurface CO 2 and energy storage containment assessment.

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Section: Methodsmentioning

confidence: 99%

Permeability heterogeneity of sandstone intrusion fluid‐escape systems, Panoche Hills, California: Implications for sedimentary basins globally

et al. 2022

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“…The second consideration involves including porosity contributions of some segmented phases from the image that could potentially have sub-resolution pores, like the clay phase shown in Figure 3 in yellow. Based on some clay mineral porosity studies [13,14], we consider here an average of 50% contribution of the volume fraction corresponding to this segmented clay phase to complement the porosity estimation.…”

Section: Estimation Of Total Porositymentioning

confidence: 99%

Towards Multiscale Digital Rocks: Application of a Sub-Resolution Production Model to a multiscale Sandstone

Salazar-Tio

Fager²,

Sun³

et al. 2023

E3S Web Conf.

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Many digital rock methodologies use a direct simulation approach, where only resolved pores are accounted for. This approach limits the types of rocks that can be analyzed, excluding some types of carbonates, unconventionals, and complex sandstones from the digital rock analysis. This is due to the challenge for single scale imaging to capture the full range of relevant pore sizes present in multiscale rocks. In this paper, a physical model is presented, within the context of an established direct simulation approach, to predict the production of hydrocarbons including the contribution of sub-resolution pores. The direct simulation component of the model employs a multiphase lattice Boltzmann method to simulate multiphase fluid flow displacement in resolved pores. In the production model, the amount of hydrocarbons present in the sub-resolution pores is identified and a physical description of the production behavior is provided. This allows a relative permeability curve to be predicted for rocks where mobile hydrocarbons are present in pores smaller than the image resolution. This simplified model for the oil movement in the unresolved pore space is based on a physical interpretation of different regions marked by simulation resolution limits in a USBM wettability test curve. The proposed methodology is applied to high-resolution microCT images of a sandstone that contains pores at multiple scales, some resolved and some not resolved. To allow for benchmarking, experimental routine and special core analysis data was also obtained. Good agreement to experimental results is observed, specifically in absolute and relative permeability. The presented multiscale model has the potential to extend the classes of reservoir rocks eligible for digital rock analysis and paves the way for further advancements in the modelling of multiscale rocks, particularly unconventionals and carbonates.

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“…Pore space within the clay mineral fraction is dominated by disconnected intragranular pores (Milliken and Curtis, 2016). Diagenetic kaolinite, depending on its texture, has microporosity up to 61% (Hurst and Nadeau, 1995), with blocky compact kaolinite minerals presenting an average microporosity of 20% (Alansari et al, 2019). By adding the estimated microporous volume, the XCT-derived total porosity increases to ~20.5%, compared to a helium-derived value of ~28%.…”

Section: Physical-versus Xct-based Porosity Measurements and Role Of ...mentioning

confidence: 99%

Experimental Simulation of Burial Diagenesis and Subsequent 2D-3D Characterization of Sandstone Reservoir Quality

et al. 2022

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Characterization of deeply buried sandstones and their reservoir quality is of paramount importance for exploring, developing, and subsurface storage of energy resources. High reservoir quality in deeply buried sandstones is commonly correlated with the occurrence of grain coatings that inhibit quartz cementation. The development of reliable models that can predict reservoir quality relies on incorporating quantitative understanding of these diagenetic processes. Hydrothermal experiments simulating burial diagenesis were integrated with multi-scale X-ray tomography to quantify the 3-dimensional evolution of grain coating volume and porosity with increasing temperature; while microscopic and automated quantitative mineralogy analysis were used to track the associated mineralogical alterations. To simulate reservoir evolution, sandstone samples from the Lower Jurassic Cook Formation (Oseberg Field, 30/6-17R, Norway) were exposed to a silica supersaturated Na2CO3 (0.1 M) solution for up to 360 h at temperatures of 100–250°C. The experimental results show the main porosity and permeability reduction window is associated with pore-filling kaolinite, and lies between 150 and 200°C, above which little change occurs. Volumetric increases in grain coating start to occur at ∼150°C through precipitation of authigenic chlorite, and continue to 250°C, irrespective of the experimental duration. Together with preexisting siderite coatings, the newly precipitated chlorite prevents the loss of reservoir quality by inhibiting quartz overgrowth development. Pore flow simulations based on the observed temperature-dependent 3-dimensional pore networks allow us to characterize pore-throat and permeability evolution and gain quantitative understanding of the impact of diagenetic overprinting on deeply buried sandstone reservoirs.

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Quantification of clay mineral microporosity and its application to water saturation and effective porosity estimation: A case study from Upper Ordovician reservoir, Libya

Cited by 10 publications

References 8 publications

Permeability heterogeneity of sandstone intrusion fluid‐escape systems, Panoche Hills, California: Implications for sedimentary basins globally

Permeability heterogeneity of sandstone intrusion fluid‐escape systems, Panoche Hills, California: Implications for sedimentary basins globally

Towards Multiscale Digital Rocks: Application of a Sub-Resolution Production Model to a multiscale Sandstone

Experimental Simulation of Burial Diagenesis and Subsequent 2D-3D Characterization of Sandstone Reservoir Quality

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