Porosity analysis of drill cuttings for seeking out reservoir formations suitable for CO2 geological storage in Gunsan Basin, West Sea of Korea

This study addresses the evaluation of lithology and porosity of 155 and 171 drill-cuttings obtained respectively from Inga-1 and Kachi-1 boreholes in order to screen deep saline reservoir formations suitable for storing CO2 in the Gunsan Basin, offshore Korea. The sedimentary succession ofKachi-1 consists mainly of Early and Late Cretaceous rocks. The upper part of the Late Cretaceous succession is truncated by the regional middle Miocene unconformity. The porosity range of the Cretaceous succession is 8.65 +/- 12.42% with minor variations along the depth. It is expected that the Cretaceous succession in the West Subbasin, where Kachi-1 was drilled, has poor injectivity due to its low porosity and tight texture. The Inga-1 was drilled in the East Subbasin and penetrated the Early Cretaceous basaltic and volcaniclastic rocks (2,728 similar to 4,103 m) in the lower part. The overlying succession (2,316 similar to 2,728 m) is dominated by fine-grained deposits and has low porosity less than 10 %. It is, however, overlain by a thick sedimentary succession (506 similar to 2,316 m) with relatively high porosity (about 10 similar to 20%). Within this succession, the section from 1,767.8 to 1,959.9 m has relatively high content of sandstone with the porosity and depth suitable for storing a great amount of CO2 in supercritical phase. The Early Miocene succession ranging from 506 to 917.5 m in depth is interpreted to contain porous sandstones, but its distribution and thickness are quite limited to the area surrounding Inga-1 borehole. We suggest to drill the northern part of the East Subbasin where the Early Miocene succession is relatively thick and extensive for evaluating its CO2 geological storage potential in the Gunsan Basin.