Production potential and stability of hydrate-bearing sediments at the site GMGS3-W19 in the South China Sea: A preliminary feasibility study

• Published in: Marine and Petroleum Geology
• Main Authors: Sun, Jiaxin, Zhang, Ling, Ning, Fulong, Lei, Hongwu, Liu, Tianle, Hu, Gaowei, Lu, Hailong, Lu, Jingan, Liu, Changling, Jiang, Guosheng, Liang, Jinqiang, Wu, Nengyou
• Other Authors: Ning, FL; Wu, NY (reprint author), China Univ Geosci, Fac Engn, Wuhan 430074, Hubei, Peoples R China., China Univ Geosci, Fac Engn, Wuhan 430074, Hubei, Peoples R China., Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266071, Peoples R China., Chinese Acad Sci, Inst Rock & Soil Mech, Wuhan 430071, Hubei, Peoples R China., Qingdao Inst Marine Geol, Key Lab Gas Hydrate, Minist Land & Resources, Qingdao 266071, Peoples R China., Peking Univ, Coll Engn, Beijing 100871, Peoples R China., Minist Land & Resources, Guangzhou Marine Geol Survey, Guangzhou 510760, Guangdong, Peoples R China.
• Format: Journal/Newspaper
• Language: English
• Published: MARINE AND PETROLEUM GEOLOGY 2017
• Subjects: Gas hydrate; Production potential; Geomechanical response; Numerical simulation; EASTERN NANKAI TROUGH; GAS-PRODUCTION; SHENHU AREA; METHANE HYDRATE; RESERVOIR DISSOCIATION; MECHANICAL-PROPERTIES; NUMERICAL-SIMULATION; TRIAXIAL COMPRESSION; THERMAL-STIMULATION; ENERGY RESOURCE; Methane hydrate
• Online Access: https://hdl.handle.net/20.500.11897/471042; https://doi.org/10.1016/j.marpetgeo.2017.05.037

According to the preliminary geological data of gas hydrate bearing-sediments (GHBS) at site GMGS3-W19 in the third Chinese expedition to drill gas hydrates in 2015, a production model using three different recovery pressures was established to assess the production feasibility from both production potential and geomechanical response. The simulation results show that for this special Class 1 deposit, it is a little hard for gas production rate to reach the commercial extraction rate because the degree of hydrate dissociation is limited due to the low reservoir permeability and the permeable burdens. However, the free gas accumulating in the lower part of the GHBS can significantly increase gas-to-water ratio. It also generates many secondary hydrates in the GHBS at the same time. Decreasing the well pressure can be beneficial to gas recovery, but the recovery increase is not obvious. In term of geomechanical response of the reservoir during the gas recovery, the permeable burdens are conducive to reduction of the sediment deformation, though they don't facilitate the gas recovery rate. In addition, significant stress concentration is observed in the upper and lower edges of GHBS around the borehole during depressurization because of high pressure gradient, and the greater the well pressure drop, the more obvious the phenomenon. Yield failures and sand production easily take place in the edges. Therefore, in order to achieve the purpose of safe, efficient and long-term gas production, a balance between the production pressure and reservoir stability should be reached at the hydrate site. The production pressure difference and sand production must be carefully controlled and the high stress concentration zones need strengthening or sand control treatment during gas production. Besides, the sensitivity analyses show that the hydrate saturation heterogeneity can affect the production potential and geomechanical response to some extent, especially the water extraction rate and the effective stress distribution and evolution. Increasing GHBS and its underlying free gas formation permeabilities can enhance the gas production potential, but it probably introduces geomechanical risks to gas recovery operations. (C) 2017 Elsevier Ltd. All rights reserved. National High-Level Talent Special Support Plan; National Natural Science Foundation of China [41672367, 41474119]; Fok Ying Tong Education Foundation [132019]; China Geological Survey Project [DD20160216]; Qingdao National Laboratory for Marine Science and Technology [QNLM2016ORP0203] SCI(E) ARTICLE 447-473 86