• Proceedings of the Petrological Society of Korea Conference
• /
• 2001.06a
• /
• pp.111-114
• /
• 2001

• 한국석유지질학회:학술대회논문집
• /
• spring
• /
• pp.82-86
• /
• 1997

• The Journal of Engineering Geology
• /
• v.23 no.4
• /
• pp.329-340
• /
• 2013

A geologic survey of the Bukpyeong and Pohang basins, as candidate basins for the geological storage of $CO_2$, was performed to evaluate storage capacity and security. To analyze the mechanical stability of the storage reservoir and cap rocks, we measured the porosity, seismic velocity, uniaxial strength, internal frictional angle, and Young's modulus of core samples recovered from the two basins. It is costly and sometimes impossible to conduct tests over the entire range of drill holes, and continuous logging data do not yield the mechanical parameters directly. In this study, to derive the mechanical properties of geologic formations from the geophysical logging data, we determined the empirical relations between the physical properties (seismic velocity, porosity, and dynamic modulus) and the mechanical properties (uniaxial strength, internal friction angle) of the core samples. From the comparison with our core test data, the best fits to the two basins were selected from the relations suggested in previous studies. The relations between uniaxial strength, Young's modulus, and porosity of samples from the Bukpyeong and Pohang basins are more consistent with certain rock types than with the locality of the basins. The relations between the physical and mechanical properties were used to estimate the mechanical rock properties of geologic formations from seismic logging data. We expect that the mechanical properties could also be used as input data for a modeling study to understand the mechanical instability of rock formations prior to $CO_2$ injection.

• 한국해양학회지
• /
• v.29 no.2
• /
• pp.164-170
• /
• 1994

The well preserved ostracodes of the Chunbuk Formation in Pohang Basin were analyzed isotopically to understand paleoceanographic conditions of the southeastern park of Korean peninsula which Songhacdong, and Mulcheonri areas range from - 2.2 to - 0.7% (PDB), - 0.7 to 0.0% , and -20.0 to - 0.8%, and their corresponding paleotemperatures range from ca 20 to 27$^{\circ}C$ (average = 24$^{\circ}C$), 17 to 20$^{\circ}C$ (average = 18$^{\circ}C$), and 20 to 26$^{\circ}C$ (average=23$^{\circ}C$),respectively. Assuming the $\delta$/SUP 18/O composition of the Middle Miocene seawater was about - 0.34% (SMOW), the paleotemperatures of the Middle Miocene shallow seawater in the Pohang Basin was almost equal to or slightly higher than the present summer temperature (ca 16 to 20$^{\circ}C$) near Pohang area. Carbon isotopic value of Cyhere omotenipponica is - 0.8% (PDB), reflecting marine carbonate carbon composition. Carbon isotopic compositions of other ostracodes such as Aurial okumurai, Trachyleberis niitsmai, Urocythereis sp., Urocythereis cf. gorokuensis, and Acanthocythereis mutsuensis range from - 5.2 to - 3.4% (PDB), which might have secreted their shells out of equilibrium with ambient seawater. This disequilibrium was most likely to have resulted from metabolic (=vital) effect, rather than temperature of productivity.

• The Korean Journal of Petroleum Geology
• /
• v.5 no.1_2 s.6
• /
• pp.48-58
• /
• 1997

Core samples from the B, E, F, H wells in the Tertiary Pohang Basin were analysed for total organic carbon (TOC) content and subject to Rock-Eval pyrolysis in order to assess petroleum geochemical characteristics of organic matter. Following geochemical screening, we selected samples from each well for the study of bitumen and kerogens such as optical observation, infra-red spectroscopy and biomarker analyses. Sediments of the Tertiary Yonil Group contain total organic carbon ranging from $0.55{\%} to 3.74{\%}$ with S1+S2 values higher than 2mgHC/g Rock in B, E and F wells, which indicates fair hydrocarbon generation potential. Most organic matter in the B, E, F wells is compared to type II based on the Rock-Eval pyrolysis, infra-red spectroscopy and optical observation. However, organic matter in the H well is compared to type III because the well is located at the margin of the basin where the preservation of terrestrial material is dominant. Geochemical analyses show that organic matter in the Yonil Group is thermally immature although thermal maturity slightly increases with depth. Maturity levels of the extracted kerogens are similar to those of bulk samples ($Tmax<435^{\circ}C$. Petroleum geochemical charateristics of the sediments in the Tertairy Yonil Group is fair in terms of the organic richness and hydrocarbon genetic potential, but organic matter is thermally immature due to the shallow burial depth. Optical observation of the kerogens and biomarker analysis show that organic matter in the Yonil Group is both marine and terrestrial origin, although it was deposited in marine environment. Pristane/phytane ratio suggests rather anoxic depositional environment. Transitional characteristics of organic matter indicate that the marine Yonil Group was deposited near the terrestrial environments. Input of terrestrial organic matter is more prevalent in the samples recovered from the lowermost horizon in the wells due to the terrestrial environment at the time of basin formation.

• The Korean Journal of Petroleum Geology
• /
• v.1 no.1 s.1
• /
• pp.15-27
• /
• 1993

Seismic reflection profiles from the eastern continental margin of Korea delineate three major Neogene sedimentary basins perched on the shelf and slope regions: Pohang-Youngduk, Mukho and Hupo basins. The stratigraphic and structural analyses demonstrate that the formation and filling of these basins were intimately controlled by two phases of regional tectonism: transtensional and subsequent contractional deformations. In the Oligocene to Early Miocene, back-arc opening of the East Sea induced extensional shear deformation with dextral strike-slip movement along right-stepping Hupo and Yangsan faults. During the transtensional deformation, the Pohang-Youngduk Basin was formed by pull-apart opening between two strike-slip faults; in the northern part, block faulting caused to form the Mukho Basin between basement highs. As a result of the back-arc closure, the stress field was inverted into compression at the end of the Middle Miocene. Under the compressive regime, two episodes (Late Miocene and Early Pliocene) of regional deformation led to the destruction and partial uplift of the basin-filling sequences. In particular, during the second episode of compressive deformation, the Hupo fault was reactivated with an oblique-slip sense, which resulted in an opening of the Hupo Basin as a half-graben on the downthrown fault block.

• Journal of the Korean earth science society
• /
• v.31 no.6
• /
• pp.573-583
• /
• 2010

A paleobotanical study of the fossil woods has been carried out from the Tertiary Janggi Group, Pohang Basin. Three species belonging to three genera of Ulmus sp., Prunus sp., and Acer sp. were identified from the Lower Coalbearing Formation, and two species of two genera of Taxodioxylon sp. and Fagus hondoensis (Watari) from the Upper Coal-bearing Formation. As our specimens are mostly poorly preserved, it is difficult to give clear specific names, but mostly are all characteristic constitutional elements of the Miocene fossil woods in Korea. The values of mean sensitivity measured from the fossil woods of Lower and Upper Coal-bearing Formations are 0.367 and 0.370 respectively, but they are more than 0.30. Based on the present two data mentioned above, it stands to reason that there were many changes in the water supply to the roots of the woods or having influence to some degree each year because of the seasonal changes in rainfall.

• Journal of the Korean earth science society
• /
• v.29 no.4
• /
• pp.319-327
• /
• 2008

A paleobotanical study of the Metasequoia has been carried out from the Miocene Keumkwangdong Formation of the non-marine Janggi Group in the Pohang Basin. As a result of this study, deciduous leafy shoots mostly belong to a single species of Metasequoia occidentalis. This species is characterized by its opposite leaves with decurrent base, and by its presence of scale leaf at base of petiole. This species is common in the Korean Tertiary floras in Miocene age, yet it has not been recorded in the Korean Peninsula after Miocene. Based on the distribution and ecology of extant Metasequoia. it is considered that the Metasequoia might have flourished in the fluvial plains as swamp forest.

• Proceedings of the KSEG Conference
• /
• 2001.03a
• /
• pp.3-14
• /
• 2001

암석은 외력하에서 탄성 및 점탄성적 변형거동을 보인다. 크리프 특성은 일정하중하에서 시간에 대한 암석의 변형으로 장기적인 지반거동을 예측할 수 있는 중요한 요소이며 암석의 점탄성적 성질을 반영한다. 포항지역에 분포하는 미고결 퇴적암인 이암을 대상으로 암석의 기본적인 물성, 역학적 특성 및 크리프 시험을 실시하였다. 일축압축강도의 40-70% 응력수준에서 순간탄성변형률은 하중의 증가에 대하여 선형적인 관계를 보였으며, 일차 크리프변형률은 시간경과에 대하여 로그함수로 적절히 설명되었다. 일차 크리프에서 이차 크리프로 진행하는 과정을 살피기 위하여 약 5일 이상의 시간이 필요하였으며 최종 크리프 변형에 의한 파괴시의 변형률은 약 0.01로 밝혀졌다.

• Economic and Environmental Geology
• /
• v.46 no.3
• /
• pp.221-234
• /
• 2013

Laboratory experiments for the reaction with supercritical $CO_2$ under the $CO_2$ sequestration condition were performed to investigate the mineralogical and geochemical weathering process of the sandstones and mudstones in the Pohang basin. To simulate the supercritical $CO_2$-rock-groundwater reaction, rock samples used in the experiment were pulverized and the high pressurized cell (200 ml of capacity) was filled with 100 ml of groundwater and 30 g of powdered rock samples. The void space of the high pressurized cell was saturated with the supercritical $CO_2$ and maintained at 100 bar and $50^{\circ}C$ for 60 days. The changes of mineralogical and geochemical properties of rocks were measured by using XRD (X-Ray Diffractometer) and BET (Brunauer-Emmett-Teller). Concentrations of dissolved cations in groundwater were also measured for 60 days of the supercritical $CO_2$-rock-groundwater reaction. Results of XRD analyses indicated that the proportion of plagioclase and K-feldspar in the sandstone decreased and the proportion of illite, pyrite and smectite increased during the reaction. In the case of mudstone, the proportion of illite and kaolinite and cabonate-fluorapatite increased during the reaction. Concentration of $Ca^{2+}$ and $Na^+$ dissolved in groundwater increased during the reaction, suggesting that calcite and feldspars of the sandstone and mudstone would be significantly dissolved when it contacts with supercritical $CO_2$ and groundwater at $CO_2$ sequestration sites in Pohang basin. The average specific surface area of sandstone and mudstone using BET analysis increased from $27.3m^2/g$ and $19.6m^2/g$ to $28.6m^2/g$ and $26.6m^2/g$, respectively, and the average size of micro scale void spaces for the sandstone and mudstone decreased over 60 days reaction, resulting in the increase of micro pore spaces of rocks by the dissolution. Results suggested that the injection of supercritical $CO_2$ in Pohang basin would affect the physical property change of rocks and also $CO_2$ storage capacity in Pohang basin.