Integrated Approach for the Understanding of Petroleum System in Frontier Deep Water Area, Offshore Japan

Correlating biostratigraphy and palaeoceanographic changes during late Quaternary at cold seeps with gas hydrate‐free areas of the Japan Sea using foraminifera paleoecology

“…A favorable source rock was developed by high production of organic matter under anoxic conditions in the Nanatani Formation at 16-12.5 Ma and the Teradomari Formation at 12.5-8 Ma (Okui et al 2008). Coarse-grained sediments were transported to the Joetsu Basin from late Miocene to Pliocene, which became primary reservoirs in the lower Teradomari and upper Teradomari at 8-5.5 Ma, and the Shiiya Formation at 5.5-3.5 Ma (Okui et al 2008;Freire et al 2011). For example, a 15-m-thick oil column was confirmed by Okui et al (2008) in tuffaceous sandstones in the lower part of the Shiiya Formation at 5.5-3.5 Ma.…”

“…Coarse-grained sediments were transported to the Joetsu Basin from late Miocene to Pliocene, which became primary reservoirs in the lower Teradomari and upper Teradomari at 8-5.5 Ma, and the Shiiya Formation at 5.5-3.5 Ma (Okui et al 2008;Freire et al 2011). For example, a 15-m-thick oil column was confirmed by Okui et al (2008) in tuffaceous sandstones in the lower part of the Shiiya Formation at 5.5-3.5 Ma. During the middle Pliocene, the tectonic style of the eastern margin of the Japan Sea changed from the extensional to compressive (Tamaki 1998) and a series of NNE-SSW trending folds were formed (Okui et al 2008), where an incipient subduction zone extends throughout the western side of the Japanese island-arc system (Tamaki & Honza 1985).…”

“…The Joetsu Basin in the southwest of Sado Island (Fig. 1) is a rift system, which was formed during the Miocene (Suzuki 1979;Okui et al 2008), and was filled mainly by siliceous shale through the initial stage of rifting (Okui et al 2008). A favorable source rock was developed by high production of organic matter under anoxic conditions in the Nanatani Formation at 16-12.5 Ma and the Teradomari Formation at 12.5-8 Ma (Okui et al 2008).…”

“…During the middle Pliocene, the tectonic style of the eastern margin of the Japan Sea changed from the extensional to compressive (Tamaki 1998) and a series of NNE-SSW trending folds were formed (Okui et al 2008), where an incipient subduction zone extends throughout the western side of the Japanese island-arc system (Tamaki & Honza 1985). As a result, several potential hydrocarbon traps, including the Umitaka Spur and the Joetsu Knoll, were formed during this period and continuous subsidence created kitchen areas with mature source rocks (Okui et al 2008;Nakajima et al 2014).…”