• Economic and Environmental Geology
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• v.46 no.4
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• pp.359-373
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• 2013

Shale is considered as a source rock for conventional oil and gas exploration and development because shale is fine-grained detrital sedimentary rock which can preserve the organic matter better. Shale has a good sealing capacity for the petroleum trap due to its low permeability. Commercial recoveries of gas from shale in the North America based on the development of technologies of horizontal drilling and hydraulic fracturing reveal that shale also function as a effective reservoir rock. Geochemical techniques to evaluate generation potential of the hydrocarbons from organic matter in the source rocks can be applied for the exploration of the shale gas resources. To evaluate shale gas resources, it is important to understand various geochemical processes and shale characteristics controlling generation, storage and estimation of shale gas reserves. In this paper, the generation mechanism of the oil and gas from organic matter is reviewed, and geochemical techniques which can be applied for the evaluation and characterization of shale gas are introduced.

• Ocean and Polar Research
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• v.36 no.4
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• pp.383-394
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• 2014

The surface sediments from the manganese nodule exploration area of Korea in the Clarion-Clipperton fracture zone were investigated to understand the resource potential of and emplacement mechanism for rare earth elements (REEs). The sediments are categorized into three lithological units (Unit I, II and III from top to bottom), but into two groups (Unit I/II and Unit III) based on the distribution pattern of REEs. The distribution pattern of REEs in Unit I/II is similar to that of Post-Archean Australian Shale (PAAS), but shows a negative Ce anomaly and enrichment in heavy REEs (HREEs). In Unit III, the HREE enrichment and Ce anomaly is much more remarkable than Unit I/II when normalized to PAAS, which are interpreted as resulting from the absorption of REEs from seawater by Fe oxyhydroxides that were transported along the buoyant plume from remotely-located hydrothermal vents. It is supported by the PAAS-normalized REE pattern of Unit III which is similar to those of seawater and East Pacific Rise sediments. Meanwhile, the PAAS-normalized REE pattern of Unit I/II is explained by the 4:1 mixing of terrestrial eolian sediment and Unit III from each, indicating the much smaller contribution of hydrothermal origin material to Unit I/II. The studied sediments have the potentiality of a low-grade and large tonnage REE resource. However, the mining of REE-bearing sediment needs a large size extra collecting, lifting and treatment system to dress and refine low-grade sediments if the sediment is exploited with manganese nodules. It is economically infeasible to develop low-grade REE sediments at this moment in time because the exploitation of REE-bearing sediments with manganese nodules increase the mining cost.

• Economic and Environmental Geology
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• v.49 no.3
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• pp.201-212
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• 2016

Due to growing problems securing stable mineral and energy resources with international political and economic changes, China has dedicated itself to strategies and policies to enhance its stable mineral and energy resources security. China has established a rare earth elements(REE) industry policy after the abolition of the REE exports quota system. China's six large REE companies have also been integrated into REE mining, smelting and refining companies. Efforts have been increased to enhance China's energy security through unconventional oil and gas exploration and development investment, as well as effort in R&D. The country will focus on technology development and exploration to promote commercial production of unconventional oil and gas based on countries with shale gas. China is making long-term contracts and joint ventures to ensure the acquisition of reliable mineral and energy resources from abroad. Government of China has proposed a range of initiatives, such as the integration of resources development strategies and environmental development strategies, internationalization of resource management, supply diversification and advancement, strengthening industry linking strategy, grouping and diversification strategy.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.587-603
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• 2018

3-D petroleum system modeling was performed on the Jeju Basin, offshore southern Korea to analyze the hydrocarbon migration and accumulation as well as the generation and expulsion of the hydrocarbon, based on subsurface structure maps of respective sedimentary formations. The lowermost formation deposited in Eocene time was assigned as a source rock, for which a mixed kerogen of type II and III was input in the modeling of oil and gas generation in consideration of the sedimentary environment of fluvio-lacustrine condition. Initial TOC was 4% as an input, based on the analysis of the well data and sedimentary environment. The modeling results show that a considerable amount of hydrocarbons was generated and expelled from the source rocks at the western Joint Development Zone (JDZ) sub-block 4, where the hydrocarbons was migrated to the above reservoir rocks at 20 Ma. The oil and gas in the reservoir rocks of the JDZ sub-block 4 are accumulated into the prospects with closure structures that has already been formed at the nearby areas. Another generation of hydrocarbon occurs from the source rock at the eastern border area of JDZ sub-block 1 and 2, where the expulsion of the hydrocarbons occurs at 10 Ma from the source rock into the above reservoir rocks, in which the accumulation also is expected. The generation, migration and accumulation were retarded at the eastern area of the JDZ sub-block 1 and 2, compared with the area of the western JDZ sub-block 4. Based on the modeling results, it is estimated that gases migrated laterally and vertically in long distance whereas oil migrated laterally in shorter distance than gases. A substantial amount of hydrocarbon could have seeped out of the reservoir formations to the surface since the migration of oil and gas actively occurred in Miocene time before the formation of seals. However, the modeling shows that the hydrocarbon could be accumulated smoothly into the closed structures that can be formed locally by alternation of sand and shale beds.