Wellbore stability analysis during drilling through marine gas hydrate-bearing sediments in Shenhu area: A case study

Sun, Jiaxin; Ning, Fulong; Lei, Hongwu; Gai, Xuerui; Sánchez, Marcelo; Lu, Jing; Li, Yanlong; Liu, Lele; Liu, Changling; Wu, N.; He, Yong; Wu, Min

doi:10.1016/j.petrol.2018.06.032

Cited by 126 publications

(45 citation statements)

References 45 publications

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“…The reasons for the two different fracture directions considered can be summarized as follows. Natural gas hydrates in the Shenhu area of the South China Sea are distributed in poorly consolidated sediments near the seafloor, so the horizontal stress may be lower than that in the vertical direction . This situation may give rise to vertical fractures in the GHBS if fracturing technology is adopted.…”

Section: Simulation Modelmentioning

confidence: 99%

“…In this work, TOUGH + HYDRATE 62 software was employed to address this issue because the software was generally used to simulate gas recovery from hydrate reservoirs in marine and permafrost regions, 27,28,30,[63][64][65] The geomechanical response was not considered because the influence of effective stress variation on the sediment and fracture properties in GHBS at this site during depressurization is currently unclear, even though the coupled thermo-hydro-mechanical model was proposed and used to perform the coupling processes during drilling and gas recovery. 25,29,[66][67][68][69][70][71][72] However, the assigned permeability of fractures takes the influence of the effective stress into account. The latter means that the value adopted is the experimental measurement in other sediments after which the bottom hole pressure remains constant after initially decreasing (i.e., the assigned fracture permeability is measured at the corresponding effective confining pressure condition).…”

Section: Numerical Simulation Codementioning

confidence: 99%

“…Natural gas hydrates in the Shenhu area of the South China Sea are distributed in poorly consolidated sediments near the seafloor, so the horizontal stress may be lower than that in the vertical direction. 70,71 This situation may give rise to vertical fractures in the GHBS if fracturing technology is adopted. However, the occurrence of hydrates in the sediment may increase the cohesion of the deposits.…”

Section: Model Constructionmentioning

confidence: 99%

“…Therefore, the model built should handle the complex multifield coupling processes and cover different phases. In this work, TOUGH + HYDRATE software was employed to address this issue because the software was generally used to simulate gas recovery from hydrate reservoirs in marine and permafrost regions, The geomechanical response was not considered because the influence of effective stress variation on the sediment and fracture properties in GHBS at this site during depressurization is currently unclear, even though the coupled thermo‐hydro‐mechanical model was proposed and used to perform the coupling processes during drilling and gas recovery . However, the assigned permeability of fractures takes the influence of the effective stress into account.…”

Section: Simulation Modelmentioning

confidence: 99%

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Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

Sun

Ning

Liu

et al. 2019

Energy Science & Engineering

Self Cite

108

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The low permeability of silty hydrate reservoirs in the South China Sea is a critical issue that threatens safe, efficient, and long‐term gas production from these reservoirs. Hydraulic fracturing is a potentially promising stimulation technology for such low‐permeability reservoirs. Here, we assess the gas production potential of a depressurization horizontal well that is assisted by the hydraulic fracturing using numerical simulation according to field data at site SH2 in this area. In addition, the number of horizontal wells drilled is discussed if commercial production is to be performed at this site. The results show that the production potential can be significantly stimulated at the early production stage by adopting hydraulic fracturing in this reservoir due to a better depressurization effect. However, the increase in gas recovery gradually decreases with the continuous dissociation of gas hydrates, and the evolution trend is similar to that in a reservoir without stimulation during later periods of gas production because the dissociation front gradually moves away from the fractures. From the perspective of production potential, using a horizontal well scheme assisted by the hydraulic fracturing technology for gas recovery from a hydrate deposit can sharply reduce the number of operation wells, shorten the drilling operation time, and boost the economic efficiency. The horizontal well scheme may be an effective way to increase the gas yield if the application of quickly deployed horizontal wells and hydraulic fracturing techniques in such hydrate reservoirs greatly increases in the near future.

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Section: Simulation Modelmentioning

confidence: 99%

Section: Numerical Simulation Codementioning

confidence: 99%

Section: Model Constructionmentioning

confidence: 99%

Section: Simulation Modelmentioning

confidence: 99%

See 2 more Smart Citations

Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

Sun

Ning

Liu

et al. 2019

Energy Science & Engineering

Self Cite

108

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show abstract

“…Finally, the wellbore reservoir stability was analyzed from the perspective of stratum subsidence and shear failure. Sun et al [6] studied the stability of hydrate-bearing near-wellbore reservoirs under the condition of drilling fluid invasion in the Shenhu area. The results showed that the change in pore pressure and the decrease of the mechanical strength of the stratum caused by hydrate dissociation were the key factors affecting the stability of the wellbore reservoir.…”

Section: Introductionmentioning

confidence: 99%

Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments

Xia

Han

2019

JMSE

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The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is introduced into a multi-field coupled model based on continuous damage theory and multi-field coupling theory. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established. The effects of damage of hydrate-bearing sediments on the thermal field, seepage field, and mechanical field are considered. Finally, the distributions of hydrate saturation, pore pressure, damage variable, and effective stress of a near-wellbore reservoir in gas hydrate exploitation by depressurization are calculated, and the stability of a hydrate-bearing near-wellbore reservoir is analyzed using the model. Through calculation and analysis, it is found that structural damage of hydrate-bearing sediments has an adverse effect on the stability of hydrate-bearing near-wellbore reservoirs. The closer to the wellbore, the worse the reservoir stability, and the near-wellbore reservoir stability is the worst in the direction of minimum horizontal ground stress.

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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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Wellbore stability analysis during drilling through marine gas hydrate-bearing sediments in Shenhu area: A case study

Cited by 126 publications

References 45 publications

Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments

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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