Micro-CT Analysis of Pores and Organics in Unconventionals Using Novel Contrast Strategies

Fogden, Andrew; McKay, Thomas J.; Turner, Michael L.; Marathe, Rohini; Senden, Tim J.

doi:10.15530/urtec-2014-1922195

Cited by 17 publications

(10 citation statements)

References 9 publications

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“…Laminations that are somewhat darker than others may possess slightly higher porosity or higher content of OM or lower content of the denser minerals (pyrite, apatite, and calcite from Table 1). To map the plug-scale variation in total connected porosity (hosted by mineral and/or OM), the horizontal plug was saturated with the X-ray opaque liquid CH 2 I 2 (Fogden et al, 2014a(Fogden et al, , 2014b) and re-scanned in this state. Its tomogram, after post-processing and 3D registration to align it to the orientation of the Dry-state tomogram, is shown in Figure 4c-d for these same two slices as in Figure 4a-b.…”

Section: Resultsmentioning

confidence: 99%

“…The grayscale of each voxel in this difference now directly reflects the total connected (accessible) porosity within the voxel, irrespective of the sizes of sub-resolution pores contributing to it (Fogden et al, 2014a(Fogden et al, , 2014b. For this plug, the spatial variations in porosity of the matrix (intermediate to the white, 100% porous fractures and the black, 0% porous grains) are relatively slight, implying that pore volume is fairly homogeneously distributed on plug scale.…”

Section: Resultsmentioning

confidence: 99%

“…The 25 mm horizontal plug and 5 mm vertical sub-plug both underwent the steps in Figure 3a-b. After their Dry-state scans, they were removed from their aluminum-tube holders and subjected to off-line saturation with diiodomethane (CH 2 I 2 ) (Fogden et al, 2014a(Fogden et al, , 2014b. This infiltration was performed (at 22 o C) by evacuation for 1 day, intrusion by CH 2 I 2 under vacuum for 1 day, and isostatic pressurization in CH 2 I 2 at 55 MPa over 20 or 50 days for the sub-plug and plug, respectively.…”

Section: Micro-ct Imagingmentioning

confidence: 99%

“…An X-ray contrast enhancement protocol was recently developed, in which the shale sample is scanned in its dry state and again after saturation of its connected porosity with a highly attenuating liquid. Registration and subtraction of these two tomograms isolates the contribution from the pore space to yield a 3D porosity map which accounts for the volume contribution from all resolved and sub-resolution pores (Fogden et al, 2014a(Fogden et al, , 2014b. Following this non-destructive imaging, the shale sample can be ion milled for 2D SEM and EDS analysis.…”

Section: Introductionmentioning

confidence: 99%

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Applications of Multi-Scale Imaging Techniques to Unconventional Reservoirs

et al. 2015

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Understanding and prediction of hydrocarbon transport within the matrix of unconventional tight reservoirs demands an integrated imaging strategy spanning from the smallest nanoscale pores to plug scale and beyond. Recent developments in multi-scale imaging are presented for Barnett shale samples to illustrate this approach to upscaling. The utility of micro-CT imaging for shales can be extended by X-ray contrast enhancement techniques coupled with tomogram registration. In particular, saturation of a shale plug with a highly attenuating liquid and subtraction of this tomogram from the registered dry-state tomogram yields a 3D voxel map of connected porosity over the plug. The same procedure can be applied to sub-plugs sampled from the parent plug to capture micron-scale variations in porosity. This approach does not directly provide the size, shape and connectivity of individual pores, since the vast majority of shale pores remain below tomogram resolution even for small sub-plugs. Two approaches to access this higher-order information are addressed. The first uses the state of the shale sub-plug saturated with X-ray dense liquid as the starting point for dynamic micro-CT imaging of the diffusion of a second, miscible, X-ray transparent liquid into the sub-plug. This can reveal the presence of faster pathways of transport through pores of larger size or lower tortuosity. The second approach involves broad beam ion-milling of the sub-plug for acquisition of 2D BSEM image mosaics and mineral maps, and their registration into the corresponding section of the 3D tomograms. This provides a registered basis for upscaling of transport properties, e.g. simulated from small FIB-SEM cubes, to sub-plug and in turn to plug via their micro-CT porosity maps. Very high resolution SEM imaging of broken surfaces can provide useful complementary information as to the finest scale of organic-hosted nanopores. The Barnett shale samples exhibited fairly homogeneous distributions of porosity on the plug and sub-plug scales, and also displayed relatively uniform diffusion across the sub-plug, suggesting that they are amenable to characterization and upscaling using only a limited set of parameters. This homogeneity is thought to be due in significant part to the predominance of organic-hosted porosity and to the structural uniformity of these nano-scale organic pore networks.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Micro-ct Imagingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Applications of Multi-Scale Imaging Techniques to Unconventional Reservoirs

et al. 2015

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“…The hierarchical imaging workflow coupled with advanced numerical methods (hereinafter referred to as Digital Rock (DR) technology) allows for 3D mapping of pore geometry, pore connectivity, and mineral and fluid distribution, as well as first-principle-based calculation and upscaling of rock properties. The application of this technology to unconventional reservoirs has been a key focus area for a number of case studies that demonstrate great potential (Walls et al 2012, Alberts et al 2013, Korost et al 2013, Koroteev et al 2014, Fogden et al 2014). Knackstedt et al (2013) showed an image registration method that projects a 2D SEM slice to a 3D microCT image such that an integrated understanding of mineral distribution, porosity, and fluid distribution can be acquired.…”

Section: Introductionmentioning

confidence: 99%

Multi-Scale Rock Characterization and Modeling for Surfactant EOR in the Bakken

Dawson

Standnes

2015

Day 2 Wed, October 21, 2015

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Low primary recovery factors in ultratight unconventional reservoirs such as the Bakken, usually in the range of 5-15%, present a potential opportunity for developing effective and economic Enhanced Oil Recovery (EOR) methods. Identified as one of the leading EOR methods for the Bakken, surfactant injection has shown good potential in the laboratory due to its capability to alter wettability, lower interfacial tension (IFT), and reduce residual oil saturation. However, successful implementation of surfactant EOR requires in-depth characterization of the rock-fluid system at multiple scales, ranging from pore scale, to core scale, to field scale. This paper presents a comprehensive study that systematically characterizes Bakken rock properties at the pore scale and the core scale, with the goal of understanding the impact of the pore structure and static and dynamic rock properties on the EOR potential for surfactant injection.At the pore scale, high-resolution 3D X-ray microtomography (microCT) imaging was acquired to evaluate microstructure, interconnected porosity, and fluid distribution. Fluid saturation mapping, before and after surfactant Spontaneous Imbibition (SI), provides fundamental insights into pore-scale recovery efficiency.At the core scale, techniques for measuring static rock properties, including porosity, permeability, and saturation in the Middle Bakken, are reviewed, with a particular focus on measuring matrix permeability across a broad range of values. Fluid properties critical to surfactant injection, such as water salinity and oil polarity, are also discussed. Results from SI experiments are presented with the goal of evaluating imbibition rate and oil recovery with proper scaling. To address the challenges of measuring dynamic rock properties such as imbibition capillary pressure and relative permeability, a plug-scale simulation model was used to history match the laboratory experiment and derive dynamic rock properties that govern the recovery process. The calibrated model was used to address plug-scale recovery efficiency and evaluate recovery uncertainty range, providing fundamental flow characteristics that can be incorporated into upscaled field-scale studies.

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Investigation of multiphase fluid imbibition in shale through synchrotron‐based dynamic micro‐CT imaging

Peng

Xiao

2017

JGR Solid Earth

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While substantial advances were made in pore system characterization in shale in the past decade, understanding of fundamentals of multiphase fluid flow in shale remains limited. The complexity of multiphase fluid flow in shale is related to many factors including nanoscale to submicron‐scale pore systems, differences in mineralogy and associated surface wettability, heterogeneity of these properties at different scales, and possible existence of microfractures. Previous work related to fluid flow, such as permeability measurement, spontaneous imbibition, and wettability analysis, includes many simplified assumptions/hypotheses with limited consideration of small‐scale details. In addition, these studies were mostly focused on single‐phase phenomena. Direct observation of multiphase fluid flow in shale showing small‐scale details is highly desired. In this study, dynamic imaging using synchrotron‐based micro‐CT (computed microtomography) was conducted on two shale samples to investigate multiphase (oil and water) spontaneous imbibition. The results revealed many details of multiphase flow in shale, including pore connectivity, porosity and permeability layered distribution, and wettability of microfractures and pores. At the same time, results illustrate the complexity of multiphase flow in shale and gaps in understanding that need further investigation.

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Micro-CT Analysis of Pores and Organics in Unconventionals Using Novel Contrast Strategies

Cited by 17 publications

References 9 publications

Applications of Multi-Scale Imaging Techniques to Unconventional Reservoirs

Applications of Multi-Scale Imaging Techniques to Unconventional Reservoirs

Multi-Scale Rock Characterization and Modeling for Surfactant EOR in the Bakken

Investigation of multiphase fluid imbibition in shale through synchrotron‐based dynamic micro‐CT imaging

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