Elastic-wave velocity characterization of gas hydrate-bearing fractured reservoirs in a permafrost area of the Qilian Mountain, Northwest China

Lu, Qu; Zou, Changchun; Lu, Zhenyu; Yu, Changqing; Li, Ning; Zhu, Ji-chang; Zhang, Xiaohuan; Yue, Xuyuan; Mingzhe, Gao

doi:10.1016/j.marpetgeo.2016.08.017

Cited by 20 publications

(7 citation statements)

References 53 publications

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“…These boreholes were DK2-25, DK2-26, DK4-23, DK4-24, DK5-22, DK6-21, DK7-20, DK8-19, DK10-16, DK10-17, DK10-18, DK11-14, DK12-13, and DK13-11. Herein, gas hydrates were discovered in four boreholes being DK8-19, DK11-14, DK12-13, and DK13-11 [37,40,41]. The gas hydrate in the area is generally produced at the depth of 130-400 m. SEM images obtained from the area indicated that the clay exists within the sediments in two forms of dispersed clays and laminated clay [40].…”

Section: Study Areamentioning

confidence: 93%

Fractal Properties of Various Clay Minerals Obtained from SEM Images

et al. 2021

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Clay minerals significantly alter the pore size distribution (PSD) of the gas hydrate-bearing sediments and sandstone reservoir rock by adding an intense amount of micropores to the existing intragranular pore space. Therefore, in the present study, the internal pore space of various clay groups is investigated by manually segmenting Scanning Electron Microscopy (SEM) images. We focused on kaolinite, smectite, chlorite, and dissolution holes and characterized their specific pore space using fractal geometry theory and parameters such as pore count, pore size distribution, area, perimeter, circularity, and density. Herein, the fractal properties of different clay groups and dissolution holes were extracted using the box counting technique and were introduced for each group. It was observed that the presence of clays complicates the original PSD of the reservoir by adding about 1.31-61.30 pores/100 μm2 with sizes in the range of 0.003-87.69 μm2. Meanwhile, dissolution holes complicate the pore space by adding 4.88-8.17 extra pores/100 μm2 with sizes in the range of 0.06-119.75 μm2. The fractal dimension ( D ) and lacunarity ( L ) values of the clays’ internal pore structure fell in the ranges of 1.51-1.85 and 0.18-0.99, respectively. Likewise, D and L of the dissolution holes were in the ranges of, respectively, 1.63-1.65 and 0.56-0.62. The obtained results of the present study lay the foundation for developing improved fractal models of the reservoir properties which would help to better understand the fluid flow, irreducible fluid saturation, and capillary pressure. These issues are of significant importance for reservoir quality and calculating the accurate amount of producible oil and gas.

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Section: Study Areamentioning

confidence: 93%

Fractal Properties of Various Clay Minerals Obtained from SEM Images

et al. 2021

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“…Figures 3, 4 show the modeling workflow and the description of the two models, respectively. Hydrate is abundant in the seafloor and permafrost (e.g., Marín-Moreno et al, 2017), for instance, in Qilian region (China) (Qu et al, 2016), the Mount Elbert in Alaska (Pan et al, 2019), and in the Eastern Nankai Trough offshore Japan (Konno et al, 2015). These cases showed the characteristics of Model 1.…”

Section: Rock-physics Modelsmentioning

confidence: 98%

“…Chand et al (2006) use the self-consistent approximation, differential effective medium theory and consider the Biot and squirt-flow attenuation mechanisms to estimate the hydrate concentration in the Mallik area. An effective-medium model, considering different microstructures, has been considered in Liu et al (2017) and Qu et al (2016) use a model based on pennyshaped and infinite cracks. Sell et al (2016) combine tomography and 3D modeling to simulate the acoustic properties with digital rock physics, whereas Sell et al (2018) show that there is an interfacial water film between hydrate and grains through 3D micro-tomography, and a new conceptual squirt-flow model is proposed.…”

Section: Introductionmentioning

confidence: 99%

Wave Properties of Gas-Hydrate Bearing Sediments Based on Poroelasticity

Wang

Carcione

et al. 2021

Front. Earth Sci.

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Natural gas hydrates have the properties of ice with a microporous structure and its concentration in sediments highly affects the wave velocity and attenuation. Previous studies have performed investigations based on the measurements of laboratory data, sonic-log data, and field data, whereas the variation trend of wave dissipation with increasing hydrate concentration at different frequencies is still unclear. We consider two different models to study this problem, both based on the Biot-Rayleigh double-porosity theory. In the first model, hydrate is part of the pore infill, unbonded from the grains, and brine saturates the remaining pore space. In the second model, hydrate forms a second skeleton and cements the grains. We obtain the P-wave velocity dispersion and attenuation as a function of the inclusion radius, porosity, and hydrate content. The analysis shows that the predictions of both models agree with the experimental data. At sonic log frequencies, the second model predicts much more attenuation, due to wave-induced local fluid flow (mesoscopic loss), and the behavior is such that below a given hydrate concentration the dissipation increases and then decreases beyond that concentration.

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“…The electrical characteristics of reservoir rocks play an important role in the exploration and development of oil and gas resources [1][2][3][4]. Up to now, extensive research has been conducted on the electrical characteristics of rocks with intergranular porosity, achieving relatively good research results, mainly focused on the electrical characteristics of rocks with approximately homogeneous features in conventional oil and gas reservoirs [5][6][7][8], and did not pay much attention to fractured gas hydrate reservoirs [9][10][11], which consist of porous layers and fractured layers and mixed with gas hydrate that distribute in different pore habits [12][13][14][15]. However, gas hydrate, which was considered one of the most promising clean energy, is mainly distributed in deep-sea sediments and terrestrial permafrost [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

A Study on the Electrical Characteristics of Fractured Gas Hydrate Reservoirs Based on Digital Rock Technology

Xue²,

Xianghui³

et al. 2021

Lithosphere

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The electrical characteristics of fractured gas hydrate reservoirs were investigated through the diffusion-limited aggregation model, digital rock technology, and the finite element method. The results show that the fracture and gas hydrate have a significant effect on the electrical characteristics of rock partially saturated with gas hydrate, where the matrix pore and fracture mixed gas hydrate form a dual-porosity system. Due to the fracture and gas hydrate effect, the electrical characteristics of fractured gas hydrate reservoirs cannot be described well by traditional Archie equations. The resistivity index vs. water saturation curve of fractured gas hydrate reservoirs shows a nonlinear relationship for different gas hydrate pore habits (pore-filling, cementing, and grain-coating types), and this curve consists of two parts with different gas hydrate saturation exponents for pore-filling and cementing gas hydrate and presents a curve without a fixed water saturation exponent for grain-coating gas hydrate. Fractured gas hydrate reservoirs with different fracture apertures, different gas hydrate pore habits, and saturation features will lead to macroscopic electrical anisotropy. The results of theoretical analysis and numerical simulation show that the electrical anisotropy coefficient of fractured gas hydrate reservoirs is a function of gas hydrate saturation. The function curve consists of three segments with the turning point for pore-filling and cementing gas hydrate, and this curve can be divided into two parts through the turning point. The findings of this study can help for a better understanding of the electrical characteristics of fractured gas hydrate reservoirs, which have great significance for the exploration and development of gas hydrate resources.

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Elastic-wave velocity characterization of gas hydrate-bearing fractured reservoirs in a permafrost area of the Qilian Mountain, Northwest China

Cited by 20 publications

References 53 publications

Fractal Properties of Various Clay Minerals Obtained from SEM Images

Fractal Properties of Various Clay Minerals Obtained from SEM Images

Wave Properties of Gas-Hydrate Bearing Sediments Based on Poroelasticity

A Study on the Electrical Characteristics of Fractured Gas Hydrate Reservoirs Based on Digital Rock Technology

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