Deep exploration of the Niigata region

Abstract

Ministry of International Trade and Industry (MITI) and Ministry of Economy, Trade, and Industry (METI) wells in the Niigata basin have been providing invaluable data on the conditions of future potential hydrocarbon traps in the deeper part of the basin. In the MITI-Niigata Heiya well, the large amount of core data provided rock properties which are required to consider the standard lithostatic pressure of the basin. The results of the MITI-Mishima well gave useful indicators concerning maturity level of source rocks, as well as realization of difficulties to interpret seismic sections of steep folded zone. The MITI Higashiyama well, which was drilled in the western part of the Higashiyama anticline, showed the existence of faulted block structures below the thick and steep surface limb. Using the MITI and METI wells, together with the other wells drilled by private oil companies, this paper presents some assumptions in order to discuss the seal potential, the structural analysis, and the fracture distributions in the deeper part of the Niigata basin. The different ways of fracture development in acidic rock and in mafic rock of the deeper part of the basin support the idea that the ductility contrast of rocks creates the environment in which remnant stress and the distribution of natural fractures are controlled in deep-sited conditions. In Japanese