Multiphase Flow Behavior of Layered Methane Hydrate Reservoir Induced by Gas Production

Gas hydrates are expected to be a potential energy resource with extensive distribution in the permafrost and in deep ocean sediments. The marine gas hydrate drilling explorations at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate deposits. Gas hydrate reservoirs are composed of alternating beds of sand and clay, with various conditions of permeability, porosity, and hydrate saturation. This study looks into the multiphase flow behaviors of layered methane hydrate reservoirs induced by gas production. Firstly, a history matching model by incorporating the available geological data at the test site of the Eastern Nankai Trough, which considers the layered heterogeneous structure of hydrate saturation, permeability, and porosity simultaneously, was constructed to investigate the production characteristics from layered hydrate reservoirs. Based on the validated model, the effects of the placement of production interval on production performance were investigated. The modeling results indicate that the dissociation zone is strongly affected by the vertical reservoir’s heterogeneous structure and shows a unique dissociation front. The beneficial production interval scheme should consider the reservoir conditions with high permeability and high hydrate saturation. Consequently, the identification of the favorable hydrate deposits is significantly important to realize commercial production in the future.

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Comparison of Simplistic and Geologically Descriptive Production Modeling for Natural-Gas Hydrate by Depressurization

SPE Journal ◽

10.2118/194214-pa ◽

2019 ◽

Vol 24 (02) ◽

pp. 563-578 ◽

Cited By ~ 3

Author(s):

Yilong Yuan ◽

Tianfu Xu ◽

Yingli Xia ◽

Xin Xin

Keyword(s):

Gas Hydrate ◽

History Matching ◽

Nankai Trough ◽

Flow Behavior ◽

Test Site ◽

Gas Production ◽

Production Test ◽

Hydrate Reservoir ◽

Hydrate Saturation ◽

Production Modeling

Summary Marine-gas-hydrate-drilling exploration at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate accumulations, which are composed of alternating beds of sand, silt, and clay in sediments, with vertically varying porosity, permeability, and hydrate saturation. The main purposes of this work are to evaluate gas productivity and identify the multiphase-flow behavior from the sedimentary-complex hydrate reservoir by depressurization through a conventional vertical well. We first established a history-matching model by incorporating the available geological data at the offshore-production test site in the Eastern Nankai Trough. The reservoir model was validated by matching the fluid-flow rates at a production well and temperature changes at a monitoring well during a field test. The modeling results indicate that the hydrate-dissociation zone is strongly affected by the reservoir heterogeneity and shows a unique dissociation front. The gas-production rate is expected to increase with time and reach the considerable value of 3.6 × 104 std m3/d as a result of the significant expansion of the dissociation zone. The numerical model, using a simplified description of porosity, permeability, and hydrate saturation, leads to significant underestimation of gas productivity from the sedimentary-complex hydrate reservoir. The results also suggest that the interbedded-hydrate-occurrence systems might be a better candidate for methane (CH4) gas extraction than the massive hydrate reservoirs.

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An Early-Time Model for Drawdown Testing of a Hydrate-Capped Gas Reservoir

SPE Reservoir Evaluation & Engineering ◽

10.2118/108971-pa ◽

2009 ◽

Vol 12 (04) ◽

pp. 595-609 ◽

Cited By ~ 6

Author(s):

Shahab Gerami ◽

Mehran Pooladi-Darvish

Keyword(s):

Gas Hydrate ◽

Gas Production ◽

Production Performance ◽

Gas Reservoir ◽

Unconventional Gas ◽

Free Gas ◽

Hydrate Decomposition ◽

Hydrate Reservoir ◽

Wellbore Pressure ◽

Hydrate Reservoirs

Summary Development of natural gas hydrates as an energy resource has gained significant interest during the past decade. Hydrate reservoirs may be found in different geologic settings including deep ocean sediments and arctic areas. Some reservoirs include a free-gas zone beneath the hydrate and such a situation is referred to as a hydrate-capped gas reservoir. Gas production from such a reservoir could result in pressure reduction in the hydrate cap and endothermic decomposition of hydrates. Well testing in conventional reservoirs is used for estimation of reservoir and near-wellbore properties. Drawdown testing in a hydrate-capped gas reservoir needs to account for the effect of gas from decomposing hydrates. This paper presents a 2D (r,z) mathematical model for a constant-rate drawdown test performed in a well completed in the free-gas zone of a hydrate-capped gas reservoir during the earlytime production. Using energy and material balance equations, the effect of endothermic hydrate decomposition appears as an increased compressibility in the resulting governing equation. The solution for the dimensionless wellbore pressure is derived using Laplace and finite Fourier cosine transforms. The solution to the analytical model was compared with a numerical hydrate reservoir simulator across some range of hydrate reservoir parameters. The use of this solution for determination of reservoir properties is demonstrated using a synthetic example. Furthermore, the solution may be used to quantify the contribution of hydrate decomposition on production performance. Introduction In recent years, demands for energy have stimulated the development of unconventional gas resources, which are available in enormous quantities around the world. Gas hydrate as an unconventional gas resource may be found in two geologic settings (Sloan 1991):on land in permafrost regions, andin the ocean sediments of continental margins. During the last decade, extensive efforts consisting of detection of the hydrate-bearing areas, drilling, logging, coring of the intervals, production pilot-testing, and mathematical modeling of hydrate reservoirs have been pursued to evaluate the potential of gas production from these gas-hydrate resources.

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SS Gas Hydrate: Prediction of Production Test Performances in Eastern Nankai Trough Methane Hydrate Reservoirs Using 3D Reservoir Model

10.4043/20737-ms ◽

2010 ◽

Cited By ~ 9

Author(s):

Masanori Kurihara ◽

Akihiko Sato ◽

Hisanao Ouchi ◽

Hideo Narita ◽

Takao Ebinuma ◽

...

Keyword(s):

Gas Hydrate ◽

Methane Hydrate ◽

Nankai Trough ◽

Production Test ◽

Reservoir Model ◽

Hydrate Reservoirs

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Numerical Modelling of Gas Production from the Oceanic Gas Hydrate Reservoirs in Eastern Nankai Trough (AT1 site), Japan

Environmental Geotechnics ◽

10.1680/jenge.19.00177 ◽

2020 ◽

pp. 1-9

Author(s):

Yongchang Feng ◽

Lin Chen ◽

Sukru Merey ◽

K P Lijith ◽

Devendra N Singh ◽

...

Keyword(s):

Numerical Modelling ◽

Gas Hydrate ◽

Nankai Trough ◽

Gas Production ◽

Hydrate Reservoirs

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Mechanical Response of Reservoir and Well Completion of the First Offshore Methane-Hydrate Production Test at the Eastern Nankai Trough: A Coupled Thermo-Hydromechanical Analysis

SPE Journal ◽

10.2118/191145-pa ◽

2018 ◽

Vol 24 (02) ◽

pp. 531-546 ◽

Cited By ~ 4

Author(s):

Jun Yoneda ◽

Akira Takiguchi ◽

Toshimasa Ishibashi ◽

Aya Yasui ◽

Jiro Mori ◽

...

Keyword(s):

Gas Hydrate ◽

Mechanical Response ◽

Nankai Trough ◽

Water Pressure ◽

Compressive Force ◽

Gas Production ◽

Production Test ◽

Frictional Stress ◽

Well Completion ◽

Hydrate Saturation

Summary During gas production from offshore gas-HBS, there are concerns regarding the settlement of the seabed and the possibility that frictional stress will develop along the production casing. This frictional stress is caused by a change in the effective stress induced by water movement caused by depressurization and dissociation of hydrate as well as gas generation and thermal changes, all of which are interconnected. The authors have developed a multiphase-coupled simulator by use of a finite-element method named COTHMA. Stresses and deformation caused by gas-hydrate production near the production well and deep seabed were predicted using a multiphase simulator coupled with geomechanics for the offshore gas-hydrate-production test in the eastern Nankai Trough. Distributions of hydrate saturation, gas saturation, water pressure, gas pressure, temperature, and stresses were predicted by the simulator. As a result, the dissociation of gas hydrate was predicted within a range of approximately 10 m, but mechanical deformation occurred in a much wider area. The stress localization initially occurred in a sand layer with low hydrate saturation, and compression behavior appeared. Tensile stress was generated in and around the casing shoe as it was pulled vertically downward caused by compaction of the formation. As a result, the possibility of extensive failure of the gravel pack of the well completion was demonstrated. In addition, in a specific layer, where a pressure reduction progressed in the production interval, the compressive force related to frictional stress from the formation increased, and the gravel layer became thin. Settlement of the seafloor caused by depressurization for 6 days was within a few centimeters and an approximate 30 cm for 1 year of continued production.

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