Multimodal study of the impact of stimulation pH on shale pore structure, with an emphasis on organics behavior in alkaline environments

Medina-Rodriguez, Bryan X.; Frouté, Laura; Alvarado, Vladimir; Kovscek, Anthony R.

doi:10.1016/j.fuel.2022.125649

Cited by 5 publications

(4 citation statements)

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“…The X-ray diffraction analysis encompassed a 2θ scan range spanning from 3° to 45°, with a step size of 0.02° and a scanning rate increment of 2° per minute. The mineralogical compositions were quantitatively determined by analyzing the XRD patterns using JADE software . The relative mineralogical contents were calculated according to the Chinese Oil and Gas Industry Standard, specifically the “Analysis Method for Clay Minerals and Ordinary Nonclay Minerals in Sedimentary Rocks by X-ray Diffraction” (SY/T5163-2018) was used…”

Section: Samples and Methodsmentioning

confidence: 99%

“…The mineralogical compositions were quantitatively determined by analyzing the XRD patterns using JADE software. 78 The relative mineralogical contents were calculated according to the Chinese Oil and Gas Industry Standard, specifically the "Analysis Method for Clay Minerals and Ordinary Nonclay Minerals in Sedimentary Rocks by Xray Diffraction" (SY/T5163-2018) was used. 79 15 °C, utilizing a Micromeritics porosimetry system (ASAP 2020, Micromeritics, USA), over a range of relative pressures (P/P 0 ) spanning from 0 to 0.995.…”

Section: Toc and Mineralogymentioning

confidence: 99%

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From Micropores to Macropores: Investigating Pore Characteristics of Longmaxi Shale in the Sichuan Basin

Hu,

Liu,

Zhang

et al. 2024

Energy Fuels

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Pore characteristics are crucial in the occurrence, aggregation, migration, and potential for CO 2 sequestration in shale gas reservoirs. We employed N 2 adsorption/ desorption, CO 2 adsorption, mercury intrusion porosimetry (MIP), focused ion beamscanning electron microscopy (FIB-SEM), and three-dimensional reconstruction of FIB-SEM images to characterize the pore characteristics in the Longmaxi Formation of the Sichuan Basin, southwestern China. These methods allowed for the detailed study of microstructure, porosity, and permeability down to the micropore scale (<2 nm). Meanwhile, N 2 and CO 2 isotherm analyses revealed a range of pore sizes, including micropores, mesopores (2−50 nm), and macropores (>50 nm). Micropores significantly contribute to the specific surface area, while mesopores and macropores predominantly contribute to pore volume. MIP results indicated extremely high pore tortuosity and connected porosity less than 1.43%. FIB-SEM and its three-dimensional reconstructions showed significant pore distribution within organic matter. At the FIB-SEM resolution (5 and 10 nm), pore connectivity is notably poor, with many large pores several hundred nanometers in diameter, undetected by the N 2 isotherm method. Permeabilities estimated by FIB-SEM are 1−2 orders of magnitude lower than those measured by MIP, exhibiting anisotropy. Assessments of gas in place and CO 2 storage capacity suggest that porosity evaluations via MIP may underestimate the quantifiable gas content in shale formations. The combined use of N 2 adsorption/desorption, CO 2 adsorption, MIP, and FIB-SEM techniques for integrating pore size characteristics offers a holistic perspective of the pore size spectrum in shale gas reservoirs, effectively addressing the limitations inherent in each individual method.

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Section: Samples and Methodsmentioning

confidence: 99%

Section: Toc and Mineralogymentioning

confidence: 99%

From Micropores to Macropores: Investigating Pore Characteristics of Longmaxi Shale in the Sichuan Basin

Hu,

Liu,

Zhang

et al. 2024

Energy Fuels

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“… 7 However, it has limited applicability to HSR reservoirs, necessitating the establishment of an appropriate pore size classification standard. Various techniques and methods are available to characterize the pore size distribution and pore throats of HSR, including mercury intrusion capillary pressure (MICP), 8 low-temperature N 2 adsorption (LTNA/D), 9 carbon dioxide gas adsorption (LPA), low-field nuclear magnetic resonance (NMR), 10 ray methods (such as small-angle X-ray scattering (SAXS)), and image methods (such as field-emission scanning electron microscopy (FE-SEM), 11 focused ion beam scanning electron microscopy (FIB-SEM), and broad ion beam scanning electron microscopy (BIB-SEM) 12 ). Among these, the MICP method is particularly useful for revealing the complex pore structure of HSR.…”

Section: Introductionmentioning

confidence: 99%

Classification and Control Factors of Reservoir Types in Hybrid Sedimentary Rocks: A Case Study on Lucaogou Formation in the Jimusaer Sag, Junggar Basin

An,

Xue,

Dong

et al. 2023

ACS Omega

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Hybrid sedimentary rocks (HSR) represent a significant reservoir type in fine-grained sediments. However, the classification and understanding of HSR reservoirs, including their storage mechanisms and identification of optimal "sweet spots," have been limited due to the lack of clarity regarding the multiple sources of components and their mixing processes. This study focuses on the Lucaogou formation of Jimusaer Sag and aims to highlight the reservoir classification principles, controlling factors, and evolutionary patterns associated with the components of HSR, beginning with examining the microscopic pore structure. The analysis of the microscopic pore structure characteristics reveals the presence of five distinct reservoir types within the HSR. The quality of these reservoirs is governed by various factors, including the composition and support mode of particles, diagenesis, provenance, and sedimentary microfacies. In regions near a provenance with strong hydrodynamic conditions, the HSR predominantly exhibits type I and type II reservoirs, characterized by numerous coarse-grained components and a granular-support mode. As the distance from the provenance increases, transitioning into medium hydrodynamic conditions, the HSR shifts to an interbedded-support mode, primarily developing type III reservoirs. In areas far from the provenance with weak hydrodynamic conditions, HSR reservoir types primarily consist of type IV and type V. Additionally, diagenetic effects such as compaction and calcite cementation further deteriorate intergranular and dissolution pores, consequently diminishing reservoir quality. Notably, during the mixing deposition processes of sand and dolomite, the developmental mode of HSR shifts from type I to type II and type III. Likewise, in the mixing deposition of mud and sand, the HSR transitions from type II to type III and type IV. Similarly, the mixing deposition of dolomite and mud leads to a change in the developmental mode of HSR from type III to type IV and type V. Moreover, this study effectively predicts the occurrence of "sweet spots" using reservoir classification, which reveals their continuous distribution. These findings provide a geological foundation for evaluating "sweet spots" and testing the oil production in HSR reservoirs.

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“…Hydraulic fracturing forms artificial fractures in the shale, accompanied by the intrusion of fracturing fluids into the shale matrix. The physicochemical interactions occur between the fracturing fluid and shale, such as water sensitivity, water locking, blockage of solid residual particles, adsorption and retention of fracturing fluid, mineral dissolution, and precipitation [9][10][11][12][13][14]. In particular, the original microscopic pore structure is altered due to the retention of the fracturing fluids in the shale reservoirs, thereby restricting the stimulation effect.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Effect of Fracturing Fluids on Shale Pore Structure by Nuclear Magnetic Resonance

Zhu,

Wang,

You

et al. 2023

Minerals

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Hydraulic fracturing technology significantly enhances the productivity of shale oil and gas reservoirs. Nonetheless, the infiltration of fracturing fluid into shale formations can detrimentally affect the microscopic pore structure, thereby impairing the efficacy of hydraulic stimulation. In this study, nuclear magnetic resonance (NMR) technology was utilized to conduct high-pressure soaking tests on shale specimens treated with EM30+ + guar gum mixed water and CNI nano variable-viscosity slickwater, where various concentrations of a drag reducer were utilized. Additionally, the differences in porosity, permeability, mineral composition, and iron ion concentration before and after the measurements were compared, which were used to analyze the influence on the shale’s microscopic pore structure. It features a reduction in the total pore volume after the interaction with the fracturing fluid, with the pore-throat damage degree, porosity damage degree, and permeability damage degree ranging from 0.63% to 5.62%, 1.51% to 6.84%, and 4.17% to 19.61%, respectively. Notably, EM30+ + guar gum mixed water exhibits heightened adsorption retention, alkaline dissolution, and precipitation compared to CNI nano variable-viscosity slickwater, rendering it more deleterious to shale. Moreover, higher concentrations of drag reducers, such as EM30+ or CNI-B, predominantly result in damage to the shale’s micropores. Shale compositions characterized by lower content of quartz and elevated proportions of clay minerals and iron-bearing minerals showcase augmented mineral dissolution and precipitation, consequently intensifying the shale damage. The hydration expansion of mixed-layer illite/smectite profoundly diminishes the core permeability. Consequently, the mechanisms underpinning the damage inflicted on shale’s microscopic pore structure primarily involve fracturing fluid adsorption and retention, mineral dissolution, and precipitation, such as clay minerals and iron-containing minerals.

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Multimodal study of the impact of stimulation pH on shale pore structure, with an emphasis on organics behavior in alkaline environments

Cited by 5 publications

References 50 publications

From Micropores to Macropores: Investigating Pore Characteristics of Longmaxi Shale in the Sichuan Basin

From Micropores to Macropores: Investigating Pore Characteristics of Longmaxi Shale in the Sichuan Basin

Classification and Control Factors of Reservoir Types in Hybrid Sedimentary Rocks: A Case Study on Lucaogou Formation in the Jimusaer Sag, Junggar Basin

Investigation of the Effect of Fracturing Fluids on Shale Pore Structure by Nuclear Magnetic Resonance

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