1997 Volume 62 Issue 1 Pages 3-12
The MITT (Ministry of International Trade and Industry) has been encouraging oil and gas exploration in domestic areas. In line with this policy, a “Five Year Plan for Domestic Oil and Natural Gas Resources Development” was set up in 1995 and has been renewed every five years to meet the current situation respectively. The plan comprises of both reconnaissance geophysical surveys (mainly on seismic fields) and exploratory test drillings.
During the period from 1955 through to 1994, a total of seventy-two wells were drilled by MITI for structural, stratigraphic and exploratory tests. As a result, samples, geological data and imformative knowledge, acquired from these tests, were utilized for plannning exploration by the private sector, as well as for studies and research in academic institutes of Japan.
Some highlights of MITI exploratory test wells drilled include:
1. Five wells out of a total of seventy-two resulted in success. One of them (MITI Yoshida well) could be developed for commercial production.
2. Deep seated crystalline basement rocks were found in six wells. These rocks are of mostly Cretaceous granites or metamorphics.
3. Stratigraphy and sedimentary facies were recognized in some unexplored areas.
4. Potential source rocks were discovered in some areas in Hokkaido.
5. Much information and data on Green Tuff volcanic rocks were gathered for their distribution, stratigraphy, facies changes, fracture development, reservoir properties, and rock alteration enhancing reservoir quality.
