シェールロックにおける油ガスの生成と移動, 現在の理解

抄録

“Shale Rocks” have been investigated in detail since 1970's as Source Rocks and Seal Rocks for conventional oil and gas, which promoted the understanding of “Shale Rocks”. In recent years, unconventional oil and gas, especially Shale Oil and Gas have been paid much attention as new resources. This situation is driven by the progress in enhancing technology such as hydraulic fracturing and higher oil and gas prices.
Shale Oil and Gas are actually to produce remaining oil and gas in matured Source Rocks, which could not be expelled during geological history. Therefore, the knowledge derived from Source Rocks for conventional oil and gas should be very useful for the Shale Oil and Gas development and production.
Not all Source Rocks are good for the Shale Oil and Gas. In order to be economical in current situations, the production rate after fracturing is the key. High production rate should be accomplished from the “Shale Rocks”, which have much concentration of oil and gas and brittle character rich in brittle minerals such as quartz and carbonate. Therefore, the “Shale Rocks” good for Shale Oil and Gas are older (Paleozoic and Mesozoic) marine Source Rocks with high TOC and maturity.
In order to save costs, the well for Shale Oil and Gas should be shallower. However, in order to generate oil and gas in Source Rocks, they have to bury more than 3000m, which is too deep for the Shale Oil and Gas businesses. Therefore, the Source Rocks should be uplifted shallower after the generation, which is likely to occur in onshore areas. The conditions discussed above limit the Shale Oil and Gas businesses within North American Continent now. However, they can expand to other areas in the future by using current knowledge of Source Rocks.