Assessment of gas production from natural gas hydrate using depressurization, thermal stimulation and combined methods

Song, Yongchen; Zhang, Lunxiang; Lv, Qin; Yang, Mingjun; Ling, Zheng; Zhao, Jiafei

doi:10.1039/c6ra05526e

Cited by 58 publications

(32 citation statements)

References 49 publications

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“…Case C4, with the most number of cooling steps and the longest formation time, resulted in the highest level of heterogeneity. Similar behaviour was reported recently in studies involving X-ray CT [59] and MRI scans [60] that visualized the in-situ phase distribution.…”

Section: Quantifying the Level Of Heterogeneitysupporting

confidence: 88%

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

et al. 2019

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Laboratory-created samples of methane hydrate (MH)-bearing media are a necessity because of the rarity and difficulty of obtaining naturally-occurring samples. The hypothesis that the inevitable heterogeneity in the phase saturations of the laboratory samples may lead to unreliable and non-repeatable results provided the impetus for this study, which aimed to determine the conditions under which maximum uniformity can be achieved. To that end, we designed four experiments involving different multi-stage cooling regimes (in terms of their duration and number of stages) to induce MH formation under excess-water conditions. In the absence of direct visualization capabilities, we analysed the experimental results by means of numerical simulation, which provided high-resolution predictions of the spatial distributions of the phase saturations in the cores and enabled the estimation of the parameters controlling the kinetic MH-formation behaviour through history-matching. Analysis of the numerical results indicated that, under the conditions of the experiments and with the design of the reactor, significant heterogeneities in phase saturation distributions were observed in all cases, leading to the conclusion that it is not possible to obtain cores with uniform phase saturation. Additionally, contrary to expectations, heterogeneities increased with the number of cooling stages and the duration of cooling, and this was attributed to imperfect insulation of the upper part of the reactor. A set of simulations involving perfect insulation of the reactor top confirmed the validity of this assumption: (a) predicting the formation of high-uniformity MH-bearing cores that became more homogeneous as 1 The short version of the paper was presented at ICAE2018, Aug 22-25 (2018), Hong Kong. This paper is a substantial extension of the short version of the conference paper.2 the number of cooling stages and the length of the cooling period increased; and (b) providing important information for the improvement of the standard design of the experimental apparatus for the laboratory creation of MH-bearing cores using the excess water method.

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Section: Quantifying the Level Of Heterogeneitysupporting

confidence: 88%

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

et al. 2019

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“…RST has expanded to include low-permeability oil and gas shale, as well as tight sand reservoirs [28]. The depressurization method and RST combine to exploit NGHs, which will increase the transmission rate of depressurization within NGH deposits and promote NGH decomposition in fractured zones, in addition to being conducive to the discharge of methane [23,[29][30][31].…”

Section: Significance and Feasibility Of Stimulation For Marine Ngh Rmentioning

confidence: 99%

Influence of Reservoir Stimulation on Marine Gas Hydrate Conversion Efficiency in Different Accumulation Conditions

et al. 2018

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Abstract:In this paper, we used a method of combining reservoir stimulation technique (RST) with depressurization to investigate the conversion efficiency of marine natural gas hydrate (NGH) reservoirs in the Shenhu area, on the northern slope of the South China Sea, which differ in intrinsic permeability and initial NGH saturation conditions. We also analyzed the influence of the variable-stimulation effect on marine NGH conversion efficiency in different accumulation conditions, providing a reference scheme for improving the NGH conversion efficiency in the Shenhu area. In this work, we performed calculations for the variations in CH 4 production rate and cumulative volume of CH 4 in different initial NGH saturation, intrinsic permeability, and stimulation effect conditions. Variance analysis and range analysis methods were used to analyze the significance of these key factors and their interaction. Furthermore, we investigated the sensitivity of stimulation effect on NGH conversion efficiency. The simulation results showed that the stimulation effect has a significant influence on NGH conversion efficiency, and the influence of interaction between these three factors was not obvious. Possibly most importantly, we clarified that the sparsely fractured networks (N = 3) had a better effect for higher NGH conversion efficiency under higher saturation conditions. For lower permeability cases, the influence between sparsely (N = 3) and densely (N = 5) fractured networks were similar.

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“…The combination of fracturing technology and existing methods to exploit natural gas hydrates would solve some of the problems of existing methods [17,27,37,38]. Fracturing technology is the primary mechanical solution for increasing porosity, interconnecting artificial cracks and natural cracks, and forming a mutual interconnected crack network in NGH concentrations, in order to enhance the conductivity of NGH concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…Fracturing technology is the primary mechanical solution for increasing porosity, interconnecting artificial cracks and natural cracks, and forming a mutual interconnected crack network in NGH concentrations, in order to enhance the conductivity of NGH concentrations. Depressurization and fracturing combine to exploit NGH [27,37,38], which increases the rate of the pressure drop within the NGH-saturated host strata and promotes NGH decomposition in cracked areas, in addition to being conducive to the discharge of methane. Thermal stimulation and fracturing combine to exploit NGH [27,37], as hot fluid enters NGH concentrations through the crack network and directly heats NGH to increase the mining radius and reduce heat loss.…”

Section: Introductionmentioning

confidence: 99%

“…Depressurization and fracturing combine to exploit NGH [27,37,38], which increases the rate of the pressure drop within the NGH-saturated host strata and promotes NGH decomposition in cracked areas, in addition to being conducive to the discharge of methane. Thermal stimulation and fracturing combine to exploit NGH [27,37], as hot fluid enters NGH concentrations through the crack network and directly heats NGH to increase the mining radius and reduce heat loss. For CO 2 replacement [17], CO 2 enters NGH concentrations through the crack networks.…”

Section: Introductionmentioning

confidence: 99%

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Simulation Study on the Effect of Fracturing Technology on the Production Efficiency of Natural Gas Hydrate

et al. 2017

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Natural gas hydrate (NGH) concentrations hold large reserves of relatively pure unconventional natural gases, consisting mainly of methane. Depressurization is emerging as the optimum conversion technology for converting NGH in its reservoir to its constituent water and natural gas. NGH concentrations commonly have a pore fill of over 80%, which means that NGH is a low-permeability reservoir, as NGH has displaced water in terms of porosity. Fracturing technology (fracking) is a technology employed for increasing permeability-dependent production, and has been proven in conventional and tight oil and gas reservoirs. In this work, we carried out numerical simulations to investigate the effects on depressurization efficiency of a variably-fractured NGH reservoir, to make a first order assessment of fracking efficiency. We performed calculations for the variations in original NGH saturation, pressure distribution, CH 4 gas production rate, and cumulative production under different fracturing conditions. Our results show that the rate of the pressure drop within the NGH-saturated host strata increases with increased fracturing. The CH 4 gas production rate and cumulative production are greatly improved with fracturing. Crack quantity and spacing per volume have a significant effect on the improvement of NGH conversion efficiencies. Possibly most important, we identified an optimum fracking value beyond which further fracking is not required.

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Assessment of gas production from natural gas hydrate using depressurization, thermal stimulation and combined methods

Cited by 58 publications

References 49 publications

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

Influence of Reservoir Stimulation on Marine Gas Hydrate Conversion Efficiency in Different Accumulation Conditions

Simulation Study on the Effect of Fracturing Technology on the Production Efficiency of Natural Gas Hydrate

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