Myong-Ho Park

Finding Least-Cost Paths across a Continuous Raster Surface with Discrete Vector Networks

The problem of finding the least-cost path from a source point to a destination point can be dealt with by routing across a continuous surface or routing along a discrete network. The solutions within these two contexts are linked to the use of a raster- or a vector-based least-cost path algorithm. This study presents a technique which integrates raster- and vector-based least-cost path algorithms for determining the least-cost path across a continuous raster surface with discrete vector networks. The technique incorporates ancillary vector data sets that are required to examine the travel cost at each link, connections between nodes, and the representation of intersecting links in the discrete vector network into raster-based least-cost path analysis. The integrated technique presented here is applicable to all-terrain vehicle navigation where a continuous raster surface and discrete vector networks need to be considered simultaneously in order to find least-cost paths. This paper describes the concept behind, and details of, the integrated technique. Applications of the technique with synthetic and real-world data sets are also presented. They provide proof that the technique is effective in finding least-cost paths across a continuous raster surface with discrete vector networks.

A Preliminary Evaluation on CO 2 Storage Capacity of the Southwestern Part of Ulleung Basin, Offshore, East Sea

A theoretical storage capacity is estimated on the southwestern continental shelf margin of Ulleung Basin, offshore Korea using 2D/3D multi-channel seismic and wellbore data acquired in the area over the two decades since the late 1980s. For the first time in Korea, the present study applies an efficiency factor to the capacity calculation, together with the other required parameters. For possible storage volume estimation of the study area, we interpreted the seismic data in the Gorae area from 800 m to 3,000 m below the seafloor integrated with the well data, and identified five different seismic units; the limited depth interval is considered because of fluid state of and tightness of the formation. The total volumes of each seismic unit were converted with a time-depth relation inferred from the checkshot surveys before the other required parameters including porosity and density were applied to compute the potential storage capacity. The accumulated possible storage volume from the five depositional units in the study area is estimated to be approximately 5,100 Mton (). The approaches made in this study will be applied to the rest area of the basin and other continental shelves (i.e., Yellow Sea and northern part of East China Sea) in the next phase.

Abrupt climatic changes induced by ice-rafting events in the eastern North Atlantic during the late Quaternary: stable isotope and X-ray mineralogical analyses

Stable oxygen- and carbon-isotope and X-ray mineralogical analyses are used to obtain information on ice-rafting (Heinrich) events in the eastern North Atlantic during the last glacial period. A sediment core collected from the continental slope off Portugal reveals that the X-ray mineralogy of some ice-rafted debris (IRD) layers is similar to that of the Heinrich layers H1, H2, and H4 in the North Atlantic, although the quantities of various detrital fragments are relatively low. The IRD layers are marked by a maximum abundance of planktonic foraminiferaNeogloboquadrina pachyderma (sin.), minima or lowered values of planktonic δ18O (Globigerina bulloides), and negative δ13C anomalies of benthic foraminiferaCibicidoides wuellerstorfi. Significant decreases in seasurface temperature and salinity are also characteristic. These data suggest that the icebergs passed along the western Iberian margin were of the same origin as those which led to the formation of Heinrich layers in the North Atlantic. In particular, a decrease in benthic δ13C of the IRD events implies a decreased ventilation of the North Atlantic that may have enhanced the advection of a12C-enriched intermediate water from the south. The absence of an IRD layer corresponding to the Heinrich layer H3 in the studied cores suggests that the reduction of convection in the North Atlantic prevented the iceberg drifting to the study area off Portugal during the period H3.

Estimation of the CO2 storage capacity of the structural traps in the southern Jeju Basin, offshore southern Korea, northern East China Sea

We analyzed 2-D seismic and well-log data from the southern Jeju Basin, offshore southern Korea, northern East China Sea to estimate the CO2 storage capacity of the structural traps in the area. Sand intervals with >10-m gross thickness were identified from the gamma-ray logs and their porosity was estimated from the neutron logs corrected for the shale effect. A total of 14 structural closures was delineated from the depth-converted maps of the sand intervals. Seismic inversion and multi-attribute transform were performed to predict the reservoir quality (i.e., porosity) of the closures away from the well control. The total storage capacity of the closures was estimated from the deterministic, volumetric method, based on the published storage efficiency parameters. The estimated CO2 storage capacity for the 14 closures is about 302 Mt, comparable to the CO2 emission (ca. 530 Mt) of Korea in 2009.

Inorganic and Organic Geochemical Characteristics of Devonian Bitumen Carbonate in Alberta, Canada

Inorganic and organic geochemical characteristics of Devonian bitumen carbonates in Alberta were studied using two drilling cores, Saleski 03-34-88-20w4 and Saleski 08-01-88-20w4, taken from the Core Research Center of Canada. The results of elements analyses showed high Total Inorganic Carbon, low Total Nitrogen and Total Sulfur, and Rock-Eval pyrolysis showed double peaks in the oxidation part. These mean that the Devonian bitumen carbonates are mainly composed of dolomite formed by diagenesis, and its crystal texture is dominantly subhedral to anhedral but often euhedral. Bitumen contents were 3.6~19.0% in Saleski 3-34-88-20w4 and 5.0~16.4% in Saleski 08-01-88-20w4, respectively. As samples color become dark, bitumen and Total Organic Carbon contents are generally increasing in two cores. The results of biomarker analyses showed that the contents of resins and asphaltenes were 5~28% higher than those of saturated hydrocarbon, interring that the bitumen has been heavily biodegradated. According to the results of carbon isotope analyses in each component of bitumen, asphaltenes had highest values and the others had constant values. However, their values were varied in the range of normal crude oil (-18~-30‰).

Distribution of late Quaternary tephra layers in the western part of the Ulleung Basin, East Sea

Lithologies and stratigraphic relationships of late Quaternary core sediments were examined in three piston cores, recovered from the western Ulleung Basin. The approximately 8-m long cores consist of muddy sediments that are interbedded with lapilli and ash layers. The morphological and major element compositional studies suggest that volcanic glass shards of the tephra layers are equivalent to those of fallout deposits of the Ulleung—Oki (ca. 9.3 ka), Aira—Tanzawa (ca. 22–24.3 ka), and Ulleung—Yamato (ca. 25–33 ka). The occurrence of the lapilli layers in the western Ulleung Basin implies that the known fallout distribution of pumicetype glass shards can be extended about 50 to 100 km to the west.

Geochemical analyses on bituminous carbonate reservoir in Alberta, Canada: focusing on the GC/GC-MS results of bitumen

The geochemical study on bituminous carbonate reservoir in Alberta has been performed to document the organic geochemical characteristics of the Grosmont Formation using two drilling cores (SAL 03-34 and SAL 08-01), especially focusing on the GC and GC-MS analyses. The results of GC and GC-MS analyses for the extracted organic matter (EOM) showed that all samples have been severely undergone a biodegradation process. However, the GC-MS data have displayed a little variation among the samples, which may be due to degree/type of biodegradation and the type of microbial activity. Triterpane biomarkers are present in low amounts, and steranes in even lesser amounts. Source and maturity assessments from both biomarkers are limited due to the lack of peaks by advanced biodegradation. The demethylated hopanes, which are typical of biodegraded oils, are not seen in these samples but they are apparently not unusual for the Athabasca tar sands, probably due to the specific type of post-emplacement microbial activity. Triterpanes biomarkers illustrate that a highly anoxic hypersaline source environment has contributed to the original oils, at the same time having anoxic marine carbonate/marl character. There is also tenuous evidence for a post-Triassic source according to the tricyclic terpane ratios. The steranes similarly indicate a marine, possibly carbonate-influenced source. Some of the aromatic compounds could also indicate a marine and anoxic hypersaline sourcing. The available peak ratios and patterns of EOM by GC-MS suggest high maturity, and aromatic parameters infer condensate window level with a vitrinite reflectance equivalent range of ∼0.9–1.2%. This could explain the remaining relatively light n-alkanes in the saturated GC chromatograms.

Geochemical Characteristics of Devonian Bitumen Carbonates in Alberta, Canada

The objective of this study is to investigate inorganic characteristics of Devonian bitumen carbonates in Alberta using two drilling cores, Saleski 03-34-88-20w4 and Saleski 08-01-88-20w4, taken from the Core Research Center (CRC) of Canada. The bitumen carbonates are mainly composed of less than 0.2 mm dolomites and some carbonate includes small amount of quartz and calcite. The bitumen carbonates from two cores are interpreted to have formed in similar sedimentary environments and dolomitization processes. Carbonates from Saleski 03-34-88-20w4 core were formed under higher inflow of clastic sediment than those from Saleski 08-01-88-20w4 core. Range of crystallization temperature of dolomites in the both bitumen carbonate cores is about 40~. Dolomitizing fluid of the bitumen carbonates would be Devonian seawater. Bitumen carbonates from Cairn Formation, compared with the CRC cores, have experienced a similar crystallization temperature, but dolmititizing fluid of the bitumen carbonates from Cairn Formation have been modified from the isotopic exchange with continental crust.

Exploring pore water biogeochemical characteristics as environmental monitoring proxies for a CO2 storage project in Pohang Basin, South Korea

Biogeochemical parameters of pore waters, including dissolved organic matter, nutrients, sulfate, alkalinity, and chloride are explored as convenient and sensitive proxies to monitor the CO2 geological storage sites. Five sites for a CO2 storage project in the Pohang Basin of the East Sea in South Korea were investigated for the pre-injection biogeochemical conditions of these sites. Higher dissolved organic carbon (~36 mg L-1), chromophoric and fluorescent dissolved organic matter, nutrients, and alkalinity were observed in a fluvially affected acoustic blanking site with geological faults. A general increasing downcore trend of measured DOM parameters, nutrients, and alkalinity with depth was found at the acoustic blanking site affected by riverine runoff with significant correlations among the parameters (R2: ~0.4-0.8), highlighting the impact of geological features and external inputs on the downcore biogeochemical properties. The results presented in this study suggest that DOM could be utilized as a robust and complementary biogeochemical parameter.

Analysis of Hydrocarbon Trap in the Southwestern Margin of the Ulleung Basin, East Sea

A commercial gas field was found in the southwestern continental shelf of the Ulleung Basin, East Sea in the late 1990s. To develop additional gas field, an exploration well was drilled through the coarse infill of submarine canyon near the gas field, but it was uneconomic to develop hydrocarbons. Using newly acquired deep seismic reflection and previous well data, we have identified additional geological structure which has hydrocarbon potentials below submarine canyons in the southwestern margin of the basin. Based on the interpretation of the deep seismic reflection and well data, the sequences of the study area can be classified into the syn-rift megasequence(MS1), post-rift megasequence(MS2), syn-compressional megasequence(MS3), and post-compressional megasequence(MS4) in relation to the tectonic events. MS1, deposited simultaneously with the basin formation before the middle Miocene, is characterized by chaotic seismic facies with low- to moderate-amplitude and low frequency reflections. MS2 comprises laterally continuous, low- to moderate-amplitude reflections, showing progradational stacking patterns due to high rates of sediment supply during basin expansion in the middle Miocene. MS3 is mainly composed of continuous reflections with high amplitude and moderate- to high-frequency which are interpreted as coarse-grained sediments. The coarse-grained sediments of MS3 sequence is widely truncated by several submarine canyons which filled with fine-grained sediment of MS4 to form a stratigraphic trap of hydrocarbon. Therefore, the reservoir and seal of the hydrocarbon trap in the study area are coarse-grained sediment of MS3 and submarine canyon filled with fine-grained sediment of MS4, respectively. A flat-spot seismic anomaly, which may indicate the presence of hydrocarbon, is observed within the stratigraphic trap.