Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, South China Sea

Wang, Xiujuan; Wu, Shiguo; Lee, Myung; Guo, Yiqun; Yang, Shengxiong; Liang, Jin

doi:10.1016/j.marpetgeo.2011.07.002

Cited by 100 publications

(34 citation statements)

References 49 publications

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“…South China Sea (passive continental margin) i. Sites SH-2, 23, and 27 [e.g., Matsumoto et al, 2011, and references therein;Wang et al, 2011aWang et al, , 2011bWang et al, , 2014aWang et al, , 2014bWu et al, 2011]. 10.…”

Section: Introductionmentioning

confidence: 99%

Observed correlation between the depth to base and top of gas hydrate occurrence from review of global drilling data

Riedel

Collett

2017

Geochem Geophys Geosyst

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A global inventory of data from gas hydrate drilling expeditions is used to develop relationships between the base of structure I gas hydrate stability, top of gas hydrate occurrence, sulfate‐methane transition depth, pressure (water depth), and geothermal gradients. The motivation of this study is to provide first‐order estimates of the top of gas hydrate occurrence and associated thickness of the gas hydrate occurrence zone for climate‐change scenarios, global carbon budget analyses, or gas hydrate resource assessments. Results from publically available drilling campaigns (21 expeditions and 52 drill sites) off Cascadia, Blake Ridge, India, Korea, South China Sea, Japan, Chile, Peru, Costa Rica, Gulf of Mexico, and Borneo reveal a first‐order linear relationship between the depth to the top and base of gas hydrate occurrence. The reason for these nearly linear relationships is believed to be the strong pressure and temperature dependence of methane solubility in the absence of large difference in thermal gradients between the various sites assessed. In addition, a statistically robust relationship was defined between the thickness of the gas hydrate occurrence zone and the base of gas hydrate stability (in meters below seafloor). The relationship developed is able to predict the depth of the top of gas hydrate occurrence zone using observed depths of the base of gas hydrate stability within less than 50 m at most locations examined in this study. No clear correlation of the depth to the top and base of gas hydrate occurrences with geothermal gradient and sulfate‐methane transition depth was identified.

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Section: Introductionmentioning

confidence: 99%

Observed correlation between the depth to base and top of gas hydrate occurrence from review of global drilling data

Riedel

Collett

2017

Geochem Geophys Geosyst

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“…As previous researchers have done much work on site SH2 [10–14, 40, 50], many valuable references can be used to obtain better results and verify the reliability of our research, so we select site SH2 as the research object. The water depth of site SH2 is 1232 m, and the maximum drilling depth is 245 mbsf.…”

Section: Data Set Used In the Studymentioning

confidence: 99%

“…Based on the previous research methods for the thickness of gas hydrate stability zone [51–53] and combined with the analysis of conventional log data, the gas hydrate stability zone of site SH2 is determined to be at the depth of 195 to 220 mbsf [40]. …”

Section: Data Set Used In the Studymentioning

confidence: 99%

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Acoustic Velocity Log Numerical Simulation and Saturation Estimation of Gas Hydrate Reservoir in Shenhu Area, South China Sea

Xiao

Zou

Xiang

et al. 2013

The Scientific World Journal

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Gas hydrate model and free gas model are established, and two-phase theory (TPT) for numerical simulation of elastic wave velocity is adopted to investigate the unconsolidated deep-water sedimentary strata in Shenhu area, South China Sea. The relationships between compression wave (P wave) velocity and gas hydrate saturation, free gas saturation, and sediment porosity at site SH2 are studied, respectively, and gas hydrate saturation of research area is estimated by gas hydrate model. In depth of 50 to 245 m below seafloor (mbsf), as sediment porosity decreases, P wave velocity increases gradually; as gas hydrate saturation increases, P wave velocity increases gradually; as free gas saturation increases, P wave velocity decreases. This rule is almost consistent with the previous research result. In depth of 195 to 220 mbsf, the actual measurement of P wave velocity increases significantly relative to the P wave velocity of saturated water modeling, and this layer is determined to be rich in gas hydrate. The average value of gas hydrate saturation estimated from the TPT model is 23.2%, and the maximum saturation is 31.5%, which is basically in accordance with simplified three-phase equation (STPE), effective medium theory (EMT), resistivity log (Rt), and chloride anomaly method.

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“…A common assumption in the majority of numerical studies (most often necessitated by the absence of supporting laboratory-or geophysical surveybased investigations) is that the initial spatial distributions of the various phases in the MH-6 bearing system are always homogeneous. Significant variations of hydrate saturations (SH between 0 and 100%) have been identified in the geological media in nature from the core samples extracted from Mallik site [35], Shenhu Area [36], Eastern Nankai Trough [37], and the recent Krishna Godavari Basin [22]. Furthermore, a handful of CT-scan and MRI studies on MH formation and dissociation have provided visual evidence that SH exhibit spatial variations within the HBS [38,39].…”

Section: Introductionmentioning

confidence: 99%

On the importance of phase saturation heterogeneity in the analysis of laboratory studies of hydrate dissociation

2019

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Methane hydrates (MHs) have been considered as the future source of energy because of its vast resource volume and high energy density. Energy recovery from MH-bearing sediments has attracted intensifying research activities. Fundamentally, heat transfer, fluid flow through porous media, and the kinetics of hydrate reaction are the three key processes controlling the behavior of MH dissociation and the associated fluid production. Earlier studies have suggested that heterogeneous spatial distribution of SH is inevitable in MHbearing samples synthesized in laboratory. In this paper, we extend our study to analyze numerically the simulation results from the two realizations of the samples (homogeneous and heterogeneous) to identify differences in the fluid production and to determine if they are sufficiently different. Additionally, we conduct a sensitivity analysis and a statistical analysis on the key transport and kinetic rate parameters that could affect hydrate dissociation and fluid production in the context of a heterogeneous hydrate-bearing sample, in an effort to provide insights that could lead to improved designs for laboratory experiments and (possibly) field applications. Our results suggest that the approximation of an artificial hydrate-bearing core with heterogeneous phase saturations by an assumption of uniform phase saturation distributions results in practically similar fluid production profile except for the very early stage with maximum 20.0% deviation in the water production. From the sensitivity and statistical analysis, we determine that gas production depends strongly on the kinetic rate constant, Kd 0 and the composite thermal conductivity of the hydrate-bearing sediments, λθ; while, water production is very sensitive to Kd 0 and the absolute permeability of the sandy medium, k. Understanding the effect of phase 2 heterogeneity and the relative importance of key parameters on the production behavior of hydrate-bearing sediments could provide basis for novel production technologies that lead to enhanced gas production and energy efficiency in the energy recovery process.

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Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, South China Sea

Cited by 100 publications

References 49 publications

Observed correlation between the depth to base and top of gas hydrate occurrence from review of global drilling data

Observed correlation between the depth to base and top of gas hydrate occurrence from review of global drilling data

Acoustic Velocity Log Numerical Simulation and Saturation Estimation of Gas Hydrate Reservoir in Shenhu Area, South China Sea

On the importance of phase saturation heterogeneity in the analysis of laboratory studies of hydrate dissociation

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