Multiscale Imaging and Nuclear Magnetic Resonance Pore Characterization in Unconventional Carbonate Mudrocks of the Southern Midcontinent (USA): Mississippi Lime Play

Bode, Ibukun Y.; Zhang, Chi; Berg, Beth Vanden; Grammer, G. Michael

doi:10.2110/sepmsp.112.11

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…Processes such as cementation, carbonate pressure dissolution, and clay diagenesis that remain active throughout the burial history can create isolated pores that are independent of the pore network created during sedimentation or even fractures from subsequent tectonics. In the Mississippian-age rocks of the study area, such processes have been widely recorded (Vanden Berg and Grammer, 2016;Vanden Berg et al, 2018;Bode et al, 2019). Two factors might together be contributing to the observed increase in V P pressure sensitivity with decreasing pore size.…”

Section: Size Effectsmentioning

confidence: 84%

How Nanopores Influence Dry-Frame VP Pressure Sensitivity

et al. 2021

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This paper investigates how nanopore size distribution influences dry-frame P-wave velocity (VP) pressure sensitivity. The study uses a set of twenty-three samples belonging to a single vertical core from the Mississippian-age Meramec formation of the mid-continent US. Individual samples had their facies interpreted, composition estimated, He-gas porosity (ΦHe) determined, and P-wave and S-wave transit times systematically measured for dry core-plugs in a 5–40 MPa loading and unloading cycle. Data from the unloading cycle were linearized in the log scale, and the slope of the best fitting line was considered as a representative of the dry-frame VP pressure sensitivity. A series of photomicrographs from each sample were analyzed using image processing methods to obtain the shape and size of the individual pores, which were mostly in the nanopore (10−6–10–9 m) scale. At the outset, the pore-shape distribution plots were used to identify and discard samples with excessive cracks and complex pores. When the remaining samples were compared, it was found that within the same facies and pore-shape distribution subgroups VP pressure sensitivity increased as the dominant pore-size became smaller. This was largely independent of ΦHe and composition. The paper postulates that at the nanopore scale in the Meramec formation, pores are mostly isolated, and an increase in the confining pressure increased the bulk moduli of the fluids in the isolated pores, which in turn increased the VP pressure sensitivity. The study proposes incorporating this effect quantitatively through a dual-fluid model where the part of the fluid in unconnected pores is considered compressible while the remaining is considered incompressible. Results start to explain the universal observation of why the presence of microporosity quintessentially enhances VP pressure sensitivity.

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Section: Size Effectsmentioning

confidence: 84%

How Nanopores Influence Dry-Frame VP Pressure Sensitivity

et al. 2021

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Section: Size Effectsmentioning

confidence: 84%

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Pore system characterization in diagenetically complex Mississippian-aged carbonate reservoirs (Kansas, USA)

et al. 2022

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Advanced petrophysical methods and detailed statistical analysis help to quantitatively and qualitatively characterize pore structure variations in carbonate rocks. Utilizing a core from the Mississippian limestone play in south-central Kansas, we investigated geological constraints on reservoir properties using observations of the variability in pore architecture and measured petrophysical properties, i.e., porosity, permeability, and nuclear magnetic resonance (NMR) response. The sample-set includes facies that retain their original depositional texture and rocks that have been subject to dolomitization, silicification, and dissolution to varying extents. Dominant macropore types include intercrystalline, moldic, and dissolution-enhanced vuggy porosity, whereas the dominant microporosity types are micritic and dolomitic intercrystalline micropores and nano-intercrystalline within silicified samples. The porosity-permeability relationships and T2 modal distribution of the carbonates we investigated correlate with dominant pore types depending on the extent and type of diagenetic modification. The fractal nature of pore systems in dolograinstones is not apparent in partially dolomitized samples, and pore complexity significantly decreases with increasing dolomitization. T2cutoff and bound fluid volume (BFV) estimates indicate that independent of geologic origin, small and intricate pore systems with microporosity are likely to host higher amounts of capillary-bound fluids. This relationship holds, especially among samples with nano-intercrystalline porosity. Correlation coefficients from predicting NMR-derived parameters with porosity improved from 0.1 to 0.78 by including pore architecture data and pore types in the multiple linear regression model. The results and observations presented here improve the current understanding and predictability of petrophysical parameters in carbonate rocks with complex pore systems.

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Multiscale Imaging and Nuclear Magnetic Resonance Pore Characterization in Unconventional Carbonate Mudrocks of the Southern Midcontinent (USA): Mississippi Lime Play

Cited by 3 publications

References 23 publications

How Nanopores Influence Dry-Frame VP Pressure Sensitivity

How Nanopores Influence Dry-Frame VP Pressure Sensitivity

table1.docx

Pore system characterization in diagenetically complex Mississippian-aged carbonate reservoirs (Kansas, USA)

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