Elastic parameter inversion of Longmaxi Formation shale based on the least squares method

Gao, Kepan; Liu, Xiangjun; Xiong, Jian; Liang, Lixi

doi:10.1007/s12517-021-06657-8

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…Vertically, the Niutitang Formation is in conformable contact with the underlying Sinian Dengying Formation and the overlying Mingxinsi Formation, which constitute its direct roof and floor. In contrast to the Longmaxi Formation in the Sichuan Basin, where the shale has successfully developed (high TOC content, high over mature evolution, and formation overpressure), the Niutitang Formation in the study area has a slightly lower degree of thermal evolution and a low-pressure coefficient. − The SG flow was obtained during four wells in the early exploration, of which the gas content of well TX1 is between 1.18 and 2.77 m 3 /t, while well TM1 was ignited successfully. Still, the gas production time is short, and the gas content is below 0.5 m 3 /t, , reflecting the difference in their preservation conditions (Figures and ).…”

Section: Overview Of Regional Geologymentioning

confidence: 92%

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

Wang

et al. 2022

ACS Omega

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Shale gas (SG) wells in the Wufeng–Longmaxi Formation in northern Guizhou differ considerably in their production capacities. Preservation conditions are a crucial factor affecting the formation of SG reservoirs. In this study, the formation water (FW) in four wells in northern Guizhou was analyzed to determine the type; the Cl/Mg, Ca/Mg, and Na/Cl coefficients (C Cl/Mg, C Ca/Mg, and C Na/Cl, respectively), and the coefficient of desulfurization (C d); the SG in these wells was tested to identify its composition and the sources of its components. The results show the following: wells TX1 and CY1 contain two types (CaCl2 and NaHCO3) of FW, each with low C Na/Cl, low C d, high C Ca/Mg, and high C Cl/Mg, suggesting a high level of FW retention. The FW in wells TM1 and CD1 is of NaHCO3 type and is characterized by high C Na/Cl, high C d, low C Ca/Mg, and low C Cl/Mg, indicating a high level of connectivity between the FW and surface water. Nonhydrocarbon gases account for a high proportion of SG in composition; with a 15N value between −8.7 and −4.2‰, N2 accounts for approximately 20% of SG in wells TX1 and CY1, respectively. This result indicates the ammonification of organic matter (OM) during pyrolysis and hydrocarbon generation as sources of N2. In contrast, with a 15N value between −3.6 and 0‰, N2 accounts for over 70% of SG in wells TM1 and CD1, respectively, indicating the atmosphere, the ammonification of OM, and the presence of poor preservation conditions due to a high level of connectivity between the shale bed and the atmosphere acted as the sources of N2. The metamorphism coefficients of FW in conjunction with the SG composition and the sources of nonhydrocarbon gases can serve as auxiliary indicators of the quality of SG preservation conditions.

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Section: Overview Of Regional Geologymentioning

confidence: 92%

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

Wang

et al. 2022

ACS Omega

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“…Elastic parameter inversion is mainly based on the acoustic velocity data and the inversion method introduced in this paper. The specific inversion process, test model, and sensitivity analysis are detailed in the literature (Gao et al 2021). The unknown parameter C ij of shale before hydration was obtained, and the results are shown in Table 1.…”

Section: Elastic Parameters Inversion Of Longmaxi Formation Shalementioning

confidence: 99%

Investigation on the influence of hydration on the elastic parameters of Longmaxi Formation shale

et al. 2021

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Through hydration experiments and ultrasonic transmission experiments, analyze the influence of hydration on the shale acoustic velocity, elastic parameters, and anisotropy parameters. The relationship between the elastic parameter C ij and the hydration time is given. The results show that: (1) The hydration of shale is a continuous and gradually stable process. (2) The qP wave velocity first significantly decreases with the hydration time and then tends to be flat, and the qSH wave velocity shows a decreasing trend with the hydration time. (3) The anisotropic strength parameter ε of the Longmaxi Formation shale increases first and then decreases, and tends to be stable with hydration time, and the magnitude of the change is relatively large, but the magnitude of γ the change is small. The results provide methods and ideas for accurately obtaining shale elastic parameters and studying the influence of hydration on shale wave speed, elastic parameters and anisotropy characteristics, and have important theoretical value and practical significance.

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“…Clay minerals, as the main mineral type and the matrix of shale, cause shale to be elastically anisotropic because of their layered structure (Bailey, 1966;Weaver and Pollard, 2011). In the process of shale oil and gas exploration and development, problems such as poor fracturing effect, high development cost, and great difficulty in finding sweet spot and stabilizing the borehole wall would arise if the influence of anisotropy is ignored (Gao et al, 2021). Therefore, it is of great significance to study the anisotropic elastic properties of clay minerals for the exploration and development of shale oil and gas.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Elastic Properties of Montmorillonite With Different Layer Charge Densities and Layer Charge Distributions Through Molecular Dynamic Simulation

Han

2022

Front. Earth Sci.

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The knowledge of the anisotropic elastic properties of clay minerals is of crucial importance for the exploration and development of shale oil and gas. Montmorillonite (MMT) is a common natural clay mineral with different layer charge densities and layer charge distributions due to different geological conditions. Therefore, it is important to understand the currently poorly known effect of layer charge density and layer charge distribution on the anisotropic elastic properties of MMTs. This work aims to obtain such knowledge by studying the anisotropic elastic properties of different MMTs under stratigraphic conditions through molecular dynamic simulations. We showed that the in-plane compressional coefficients C11, C22 and C12 decrease with the increasing layer charge density for MMTs with different layer charge distributions, and the MMTs with the layer charges distributed on the two tetrahedral (T) sheets were found to have the smallest C11, C22 and C12. We also showed that the out-of-plane compressional coefficients C33, C13 and C23 of the MMTs with the layer charges distributed in the two T sheets decrease, while those with the layer charges in the octahedral (O) sheet increase and those with layer charges distributed in both the O sheet and the T sheets do not vary much with the increasing layer charge density. The variations of the anisotropic compressional elastic coefficients with different layer charge densities and layer charge distributions were found to be a result of the impact of the density and distribution of layer charges on the molecular interactions within the MMT layer. We further demonstrated that the layer charge density and layer charge distribution do not influence significantly the shear coefficients C44, C55, and C66. The results revealed the mechanisms of how the density and distribution of layer charges affect the anisotropic elastic properties of MMTs and will contribute to the more successful exploration and development of unconventional resources in MMT bearing shale reservoirs.

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Elastic parameter inversion of Longmaxi Formation shale based on the least squares method

Cited by 3 publications

References 19 publications

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

Investigation on the influence of hydration on the elastic parameters of Longmaxi Formation shale

Anisotropic Elastic Properties of Montmorillonite With Different Layer Charge Densities and Layer Charge Distributions Through Molecular Dynamic Simulation

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