Nanoscale pore structure characterization of the Bakken shale in the USA

Liu, Kouqi; Ostadhassan, Mehdi; Zhou, Jie; Gentzis, Thomas; Rezaee, Reza

doi:10.1016/j.fuel.2017.08.034

Cited by 236 publications

(158 citation statements)

References 56 publications

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“…Concurrently, the pore-size distribution of a sister core, cut from the same whole core as Sample B (Akbarabadi & Piri, 2014;Akbarabadi et al, 2017), showed most of the pores to be smaller than 400 nm. This pore-size distribution is in agreement with others reported in the literature for same reservoir Liu et al, 2017;Saidian & Prasad, 2015;Zhang et al, 2013). By comparing Figure 11 with the pore-size distribution of Sample B, it is apparent that the precipitated salt crystals could easily occlude the pore space and significantly reduce the permeability of the rock.…”

Section: Resultssupporting

confidence: 93%

Salt Precipitation in Ultratight Porous Media and Its Impact on Pore Connectivity and Hydraulic Conductivity

Alizadeh

Akbarabadi

Barsotti

et al. 2018

Water Resources Research

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The degree of salt precipitation and its impact on fluid flow in ultratight porous media are investigated in three preserved core plugs selected from two different wells in an unconventional hydrocarbon reservoir. Small specimens are cut from the core plugs and then imaged using a focused ion beam scanning electron microscope (FIB‐SEM) to detect any salt precipitation in the pore space. The SEM results show that salt covers the pore walls and either partially or fully blocks pore elements, making some parts of the pore space inaccessible to flow. To examine the effect of salt removal on fluid flow, one of the core plugs is subjected to a cleaning process. The plug is initially saturated with methanol, and then methanol is continuously injected into the sample while the effluent is periodically titrated using silver nitrate to monitor salt removal. The variation of the salinity of the methanol effluent with time, the decrease in the pressure drop across the core, and the increased permeability to methanol indicated the effectiveness of the cleaning process. The successful removal of salt from the sample prompts the adoption of a new workflow for preparing tight rock samples for laboratory experiments.

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Section: Resultssupporting

confidence: 93%

Salt Precipitation in Ultratight Porous Media and Its Impact on Pore Connectivity and Hydraulic Conductivity

Alizadeh

Akbarabadi

Barsotti

et al. 2018

Water Resources Research

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“…2,32 Different sized pores within the Chang 6 reservoir samples that have different permeabilities account for different proportions of the total pore throats, and the contribution to permeability is different (Figure 7). 2,32 Different sized pores within the Chang 6 reservoir samples that have different permeabilities account for different proportions of the total pore throats, and the contribution to permeability is different (Figure 7).…”

Section: Influence On Permeabilitymentioning

confidence: 99%

“…Pore throats can be divided into nano pores (less than 0.1 μm), sub-micro pores (0.1-1 μm), and micro pores (larger than 1 μm) based on their sizes and according to the classification of pore throats in petroleum geology. 2,32 Different sized pores within the Chang 6 reservoir samples that have different permeabilities account for different proportions of the total pore throats, and the contribution to permeability is different (Figure 7). The proportion of nano pores to the total pore volume decreased with the increase of permeability, while the proportion of sub-micro pores linearly increased; when core permeability was low (less than 1 × 10 −3 μm 2 ), micro pores were almost nonexistent, and when permeability was over 1 × 10 −3 μm 2 , only a few micro pores were distributed within the sample (less than 5%).…”

Section: Influence On Permeabilitymentioning

confidence: 99%

Influence of micro‐pore structure in tight sandstone reservoir on the seepage and water‐drive producing mechanism—a case study from Chang 6 reservoir in Huaqing area of Ordos basin

Ren

et al. 2019

Energy Science & Engineering

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To study the influence of pore structure on the seepage and water‐drive producing mechanisms, various methods were combined to describe the micro‐pore structure in the Chang 6 tight sandstone reservoir in the Huaqing area, Ordos Basin, China. Nuclear magnetic resonance (NMR) was combined with displacement experiments to determine the distribution of oil and water in pores of different scales before and after water flooding. There are few micro pores in the reservoir. As permeability increases, the distribution of nano pores decreases, while sub‐micro pores increase. Also, sub‐micro pores are the main pathway within the reservoir. There is a negative power function correlation between the minimum starting pressure gradient of the oil (Swc) and maximum throat radius. Also, with a decrease of permeability, smaller pore throats become more abundant and the nonlinear section of the flow velocity‐differential pressure curves increase. There is a large amount of crude oil gathering in the nano pores. As permeability increases, the main sources of movable oil are from the nano pores (kg < 0.4 × 10−3 μm2), sub‐micro pores (kg ≈ 0.4 × 10−3 μm2‐1.0 × 10−3 μm2), and micro pores (kg > 1.0 × 10−3 μm2). Displacement efficiency is always the highest in sub‐micro pores.

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“…[31][32][33] The adsorption and desorption curves of the sampled volcanic rocks in the target layer show obvious hysteresis loops, indicating the development of nanoscale pores in the volcanic tight reservoirs of the Haerjiawu Formation in the Santanghu Basin, with strong heterogeneity. The study of the adsorption-desorption curve enables the volcanic rocks in the target layer to be divided into two types: the adsorption and desorption curves of one set of samples are convex upward at low pressure (0 < P/P 0 < 0.05), signifying adsorption of liquid nitrogen on a monolayer of a rock sample surface, or microspore filling.…”

Section: Morphological Characteristics Of the Poresmentioning

confidence: 99%

Fractal Nature of Porosity in Volcanic Tight Reservoirs of the Santanghu Basin and Its Relationship to Pore Formation Processes

Wang

Chen

et al. 2018

Fractals

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In this paper, in a case study of Santanghu Basin in China, the morphological characteristics and size distribution of nanoscale pores in the volcanic rocks of the Haerjiawu Formation were investigated using the results of low temperature nitrogen adsorption experiments. This research showed that within the target layer, a large number of nanoscale, eroded pores showed an "ink bottle" morphology with narrow pore mouths and wide bodies. The fractal dimension of pores increases gradually with increasing depth. Moreover, as fractal dimension increases, BET-specific surface area gradually increases, average pore diameter decreases and total pore volume gradually increases. The deeper burial of the Haerjiawu volcanic rocks in the Santanghu Basin leads to more intense erosion by organic acids derived from the basin's source rocks. Furthermore, the internal surface roughness of these corrosion pores results in poor connectivity. As stated above, the corrosion process is directly related to the organic acids generated by the source rock of the interbedded volcanic rocks. The deeper the reservoir, the more the organic acids being released from the source rock. However, due to the fact that the Haerjiawu volcanic rocks are tight reservoirs and have complicated pore-throat systems, while organic acids dissolve unstable minerals such as feldspars which improve the effective reservoir space; the dissolution of feldspars results in the formation of new minerals, which cannot be expelled from the tight reservoirs. They are instead precipitated in the fine pore throats, thereby reducing pore connectivity, while enhancing reservoir micro-preservation conditions.

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Nanoscale pore structure characterization of the Bakken shale in the USA

Cited by 236 publications

References 56 publications

Salt Precipitation in Ultratight Porous Media and Its Impact on Pore Connectivity and Hydraulic Conductivity

Salt Precipitation in Ultratight Porous Media and Its Impact on Pore Connectivity and Hydraulic Conductivity

Influence of micro‐pore structure in tight sandstone reservoir on the seepage and water‐drive producing mechanism—a case study from Chang 6 reservoir in Huaqing area of Ordos basin

Fractal Nature of Porosity in Volcanic Tight Reservoirs of the Santanghu Basin and Its Relationship to Pore Formation Processes

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