Based on the geophysical survey data and basin evaluation results for the area around Japan until now and the analysis of the exploratory well data drilled for resource assessment, there are porous sandy and volcano-clastic rocks in the Pleistocene and Pliocene as the formations that satisfy the conditions as a CO2 injection reservoir. For the former, it is important to evaluate the ability of the sealing layer directly above because of the shallow formation below sea bottom floor, and for the latter, it is important to evaluate the CO2 injectivity because of the deeper horizon of less permeable.

Exploratory drillings for the assessment project of oil and natural gas potential were implemented by the Ministry of International Trade and Industry (MITI) at that time, offshore Akita, and cuttings lithology description, their petrographic / mineralogy analysis for whole depth interval, sequential formation pressure measurement, well logging measurement were carried out. Referring to such geological information, we conducted well log analysis on a provided borehole data for the sake of investigating capability of CO2 injection in the drilled formations. Outline of the analysis is reported in this article, then acquisition of indispensable data of the reservoir and sealing formation in the new exploratory drillings are proposed for establishing CO2 injection reservoir model.

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