Petroleum Reservoir Evaluation and Development ›› 2023, Vol. 13 ›› Issue (6): 809-818.doi: 10.13809/j.cnki.cn32-1825/te.2023.06.012

• Comprehensive Research • Previous Articles     Next Articles

Effects of creep on depressurization-induced gas well productivity in South China Sea natural gas hydrate reservoirs

CUI Yudong1,2(),LU Cheng2,GUAN Ziyue3,LUO Wanjing1(),TENG Bailu1,MENG Fanpu1,PENG Yue1   

  1. 1. School of Energy Resources, China University of Geosciences, Beijing 100083, China
    2. Oil & Gas Survey, China Geological Survey, Beijing 100083, China
    3. Engineering Technology Research Institute, PetroChina Xinjiang Oilfield Company, Karamay, Xinjiang 834000, China
  • Received:2022-10-26 Online:2023-12-26 Published:2024-01-03


The South China Sea's natural gas hydrate reservoirs, primarily composed of clayey silt with non-diagenetic properties, undergo creep during depressurization development. The implications of this creep on key reservoir characteristics such as permeability, porosity, pressure, temperature, hydrate saturation distribution, and gas well productivity remain unclear. To address this, a combination of water seepage experiment data from clayey-silt cores and numerical simulation methods was employed to study the development of these hydrate reservoirs through depressurization-induced vertical wells. The simulation results show that the creep effects reduce the effective reservoir porosity and permeability while developing South China Sea natural gas hydrate reservoirs using a depressurization-induced vertical well. Specifically, the pressure drop is predominantly observed near the well, accompanied by a significant decrease in temperature around the well. Additionally, the reservoir creep results in a more pronounced pressure drop funnel within the reservoir. The hydrate decomposition mainly occurs at the regions of the near-well, the top of hydrate layer A, and the bottom of hydrate layer B, and the radius of hydrate decomposition is decreased by 66.7 % due to creep effects. The reservoir creep effects reduced the gas well productivity, and the cumulative production of the gas well in five years decreased by 87 %. The creep of the South China Sea natural gas hydrate reservoir dominates while the production pressure difference is greater than 4 MPa. As the production pressure difference is larger, the increasing degree of cumulative production gradually becomes smaller. A production pressure difference lower than 4 MPa is recommended for future long-term development. This study provides a reliable theoretical basis for developing South China Sea natural gas hydrate efficiently.

Key words: clayey silt, natural gas hydrate, reservoir creep, depressurization-induced, gas well productivity, numerical simulation

CLC Number: 

  • TE37