Diagenetic change of residual gas in mudstones

2014 Fiscal Year Final Research Report

• Project/Area Number: 24540484
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Hokkaido University
• Principal Investigator: SUZUKI Noriyuki 北海道大学, 理学(系)研究科(研究院), 教授 (00144692)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: シェールガス / 残留ガス / メタン / 天然ガス / 四万十帯 / 続成作用 / 変成作用

Outline of Final Research Achievements

Concentration and compositional changes of hydrocarbon gases in shale rocks and metapelites during diagenesis and metamorphism were revealed by this study. The shale rocks and metapelites were collected from borehole MITI-Mishima and outcrops in Shimanto belt, Chichibu belt, and Sanbagawa metamorphic belt in Shikoku region. Concentration of residual methane begins to increase when shale rock porosity reaches about 5%, suggesting a significant retention of methane in shale rocks. The highest concentration of residual methane corresponds to maturity levels of vitrinite refrectance (VR)=2 to 3 % (maximum heated temperature=200 to 250ºC). Residual methane concentration significantly decreases in the stage of metamorphism suggesting the graphitization of methane. The maturity level of VR=2 to 3 % is the main maturation stage for the formation of shale gas deposit. Several gas seepages observed in Shimanto belt suggest the formation of shale gas deposits in accretionary prism.

Free Research Field

石油天然ガス・堆積学