Numerical investigation on the long-term production behavior of horizontal well at the gas hydrate production site in South China Sea

Yin, Faling; Gao, Yonghai; Chen, Ye; Sun, Baojiang; Li, Shaoqiang; Zhao, Danshi

doi:10.1016/j.apenergy.2022.118603

Cited by 24 publications

(18 citation statements)

References 38 publications

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“…With the dissociation of hydrate, the effective permeability of hydrate formation changes with the change of porosity. In this study, the relationship between effective permeability and porosity is based on the Carmen-Kozeny model [42,44]:…”

Section: The Relation Between Porosity and Permeabilitymentioning

confidence: 99%

Enhanced Gas Production from Class II Gas Hydrate Reservoirs by the Multistage Fractured Horizontal Well

Sun

Li²,

He³

et al. 2023

Energies

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In the two test productions that have been conducted in the hydrate reservoir test development zone in the South China Sea, the gas production capacity of single wells is low and the exploitation difficulty with the cost is too high for commercial demand economically. The low permeability of the hydrate-bearing layer (HBL) acts as the major barrier for pressure propagation during depressurization. Hydraulic fracturing by the combined depressurization is considered a promising hydrate production enhancement technology that can effectively improve the seepage state in the reservoir. In this study, to evaluate the effectiveness of the development methods association with fracturing, we established an idealized Class II hydrate reservoir and studied it using a multi-stage fractured horizontal well to assist in depressurization extraction. In order to evaluate the production enhancement effect of this method, we compared the gas production results of four methods, including single vertical well, vertical fractured well, horizontal well, and multistage fractured horizontal well through numerical simulation. In order to investigate the influence of key fracture parameters on the production enhancement effect, a sensitivity analysis of the production effect of Class II hydrate reservoirs with different fracture spacing, number of fractures, fracture conductivity, and fracture length was conducted, and the results were analyzed in terms of gas production and water production behavior curves as well as physical field evolution over time. The simulation results show that the multi-stage fractured horizontal wells have the best production increase in the comparison of well types. In the analysis of fracture parameters, it can be found that the selection of proper fracture spacing and dimensionless fracture conductivity can lead to a significant increase in gas production.

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Section: The Relation Between Porosity and Permeabilitymentioning

confidence: 99%

Enhanced Gas Production from Class II Gas Hydrate Reservoirs by the Multistage Fractured Horizontal Well

Sun

Li²,

He³

et al. 2023

Energies

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“…The initial conditions and boundary conditions are given below. The initial pore water pressure within the reservoir follows a hydrostatic pressure gradient, with the top surface of the hydrate-bearing layer (HBL) set at an initial pressure of 14.76 MPa . The initial temperature field in the reservoir follows a geothermal gradient of 0.045 °C/m, and the seafloor temperature is 3.6 °C .…”

Section: Model Setupmentioning

confidence: 99%

“…22 (3) The effect of salinity on phase equilibrium has not been considered. 23 Under these assumptions, the mass conservation equation for each component can be expressed as 24…”

Section: Thermo-hydro-mechanical-chemical Couplingmentioning

confidence: 99%

“…The initial pore water pressure within the reservoir follows a hydrostatic pressure gradient, with the top surface of the hydrate-bearing layer (HBL) set at an initial pressure of 14.76 MPa. 23 The initial temperature field in the reservoir follows a geothermal gradient of 0.045 °C/m, and the seafloor temperature is 3.6 °C. 20 The initial in situ stress is determined by both hydrostatic and lithostatic pressures.…”

Section: Thermo-hydro-mechanical-chemical Couplingmentioning

confidence: 99%

“…To simplify the analysis, the following assumptions are made: The diffusion between methane and water is slow and contributes little to mass transfer. , Ice and secondary hydrate formation are disregarded during hydrate dissociation in the Shenhu area The effect of salinity on phase equilibrium has not been considered …”

Section: Model Setupmentioning

confidence: 99%

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Long-Term Performance and Security of Gas Production for Horizontal-Well Depressurization Exploitation: Insights from a Coupled Thermo-Hydro-Mechanical-Chemical Model for the Shenhu Hydrate Reservoir

Li,

Fan,

et al. 2023

Energy Fuels

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Horizontal-well depressurization for marine hydrate exploitation started in 2020. Short-term gas production stability (∼30 days) contrasts with ongoing uncertainties about long-term performance and security. To address these concerns, we used the 2020 Shenhu field test as a case study and created a fully coupled thermo-hydro-mechanical-chemical model. Employing this model, cumulative gas production closely matched field test data, with a deviation below 1.5%. Our numerical simulations showed the following: (1) Following depressurization initiation, the rapid increase in effective principal stress of the hydrate reservoir stabilized near the well after 30 days and at the seafloor after 2 years, without reaching failure conditions. (2) Variable effective principal stress led to complex temporal and spatial formation deformation. During the 30-day test, subsidence mostly occurred near the well (<10 cm). However, after approximately 250 days, measurable seafloor subsidence (∼3 cm) began, reaching 21 cm after 4 years. (3) Formation deformation hindered gas production. Simulations indicated reductions of 33.6 and 15.2% in cumulative gas release and production volumes, respectively, over 5 years. Our findings shed light on the interplay among depressurization, formation deformation, and gas production in marine hydrate exploitation, contributing to a better understanding of the long-term performance and dynamics of marine hydrate exploitation.

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Numerical study on gas production via a horizontal well from hydrate reservoirs with different slope angles in the South China Sea

Luo,

Song,

Sun

et al. 2024

Deep Underground Science and Engineering

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It is important to study the effect of hydrate production on the physical and mechanical properties of low‐permeability clayey–silty reservoirs for the large‐scale exploitation of hydrate reservoirs in the South China Sea. In this study, a multiphysical‐field coupling model, combined with actual exploration drilling data and the mechanical experimental data of hydrate cores in the laboratory, was established to investigate the physical and mechanical properties of low‐permeability reservoirs with different slope angles during 5‐year hydrate production by the depressurization method via a horizontal well. The result shows that the permeability of reservoirs severely affects gas production rate, and the maximum gas production amount of a 20‐m‐long horizontal well can reach 186.8 m3/day during the 5‐year hydrate production. Reservoirs with smaller slope angles show higher gas production rates. The depressurization propagation and hydrate dissociation mainly develop along the direction parallel to the slope. Besides, the mean effective stress of reservoirs is concentrated in the near‐wellbore area with the on‐going hydrate production, and gradually decreases with the increase of the slope angle. Different from the effective stress distribution law, the total reservoir settlement amount first decreases and then increases with the increase of the slope angle. The maximum settlement of reservoirs with a 0° slope angle is up to 3.4 m, and the displacement in the near‐wellbore area is as high as 2.2 m after 5 years of hydrate production. It is concluded that the pore pressure drop region of low‐permeability reservoirs in the South China Sea is limited, and various slope angles further lead to differences in effective stress and strain of reservoirs during hydrate production, resulting in severe uneven settlement of reservoirs.

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Numerical investigation on the long-term production behavior of horizontal well at the gas hydrate production site in South China Sea

Cited by 24 publications

References 38 publications

Enhanced Gas Production from Class II Gas Hydrate Reservoirs by the Multistage Fractured Horizontal Well

Enhanced Gas Production from Class II Gas Hydrate Reservoirs by the Multistage Fractured Horizontal Well

Long-Term Performance and Security of Gas Production for Horizontal-Well Depressurization Exploitation: Insights from a Coupled Thermo-Hydro-Mechanical-Chemical Model for the Shenhu Hydrate Reservoir

Numerical study on gas production via a horizontal well from hydrate reservoirs with different slope angles in the South China Sea

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