• Geosciences Journal
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• v.22 no.6
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• pp.1027-1039
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• 2018

Seismic attributes are often used to identify lithology and evaluate reservoir properties. However, interpretation based only on structural attributes and without knowledge of the Vp/Vs ratio can limit the ability to evaluate changes in heavy oil reservoirs. These limitations are often due to less obvious impedance differences. In order to investigate pieces of evidence of a heavy-oil shaly-sand reservoir from seismic data, besides geochemistry, we studied seismic attributes and characterized the reservoir using seismic stack data and well logging data. The study area was the Muglad rift basin in South Sudan. We conducted a seismic complex analysis to evaluate the target reservoir. To delineate the frequency responses of the different lithological units, we applied the spectral decomposition method to the target reservoir. The most unexpected result was continuous bands of strong seismic reflectors in the target reservoir, which extended across the borehole. Spectral decomposition analysis showed that the low-frequency zone of 25 Hz dominant frequency was consistent with instantaneous attributes. This approach can identify lithology, reveal frequency anomalies, and filter the stacked section into low- and high-frequency bands. The heavy-oil reservoir zones exhibited velocity attenuation and the amplitude was strongly frequency dependent.

• Geosciences Journal
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• v.22 no.6
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• pp.1041-1052
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• 2018

A single-well push-drift-pull tracer test using two different tracers ($SF_6$ and salt) was performed at the Environmental Impact Test (EIT) site to determine suitable locations for monitoring wells and arrange them prior to artificial $CO_2$ injection and leak tests. Local-scale estimates of hydraulic properties (linear groundwater velocity and effective porosity) were obtained at the study site by the tracer test with two tracers. The mass recovery percentage of the volatile tracer ($SF_6$) was lower than that of the non-volatile tracer (salt) and increased drift time may make degassing of $SF_6$ intensified. The $CO_2$ leakage monitoring results for both unsaturated and saturated zones suggest that the $CO_2$ monitoring points should be located near points at which a high concentration gradient is expected. Based on the estimated hydraulic properties and tracer mass recovery rates, an optimal $CO_2$ monitoring network including boreholes for monitoring the unsaturated zone was constructed at the study site.

• Geosciences Journal
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• v.22 no.6
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• pp.1053-1067
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• 2018

This paper uses a probability-based approach to study the spatial relationships between landslides and their causative factors in the Mingchukur area, Bostanlik districts of Tashkent, Uzbekistan. The approach is based on digital databases and incorporates methods including probability analysis, spatial pattern analysis, and interactive mapping. First, an object-oriented conceptual model for describing landslide events is proposed, and a combined database of landslides and environmental factors is constructed by integrating various databases within a unifying conceptual framework. The frequency ratio probability model and landslide occurrence data are linked for interactive, spatial evaluation of the relationships between landslides and their causative factors. In total, 15 factors were analyzed, divided into topography, hydrology, and geology categories. All analyzed factors were also divided into numerical and categorical types. Numerical factors are continuous and were evaluated according to their $R^2$ values. A landslide susceptibility map was constructed based on conditioning factors and landslide occurrence data using the frequency ratio model. Finally, the map was validated and the accuracy showed the satisfactory value of 83.3%.

• Geosciences Journal
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• v.22 no.6
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• pp.903-919
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• 2018

This paper focuses on the depositional processes and environmental changes during initial marine flooding recorded in the lower Cambrian succession of the North China Platform in Shandong Province, China. In order to understand imbalance of accommodation and sediment supply in the initial stage of basin-fill, a detailed analysis of sedimentary facies was made for the lowermost siliciclastic deposits of the Liguan Formation. It reveals ten siliciclastic lithofacies in three large-scale outcrops (Jinhe, Anqianzhuang, and Zhangjiapo sections). These facies are grouped into four facies associations, representing siliciclastic foreshoreshoreface (S1), siliciclastic offshore (S2), distributary mouth bars (S3), and coastal plain (S4). The siliciclastic components occur in a linear belt, emanating from a major drainage system in the northeastern part of the platform. Deposition of siliciclastic sediments was largely controlled by regional topography of the unconformable surface and shoreline configuration as well as strong effect of waves and currents. With ensued rise in sea level and decrease in siliciclastic sediment supply, carbonate sediments prevailed, filling the accommodation created by epeirogenic subsidence and sediment loading.

• Geosciences Journal
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• v.23 no.4
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• pp.547-556
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• 2019

A new species of the most primitive rosenellid stromatoporoid Cystostroma, C. primordia sp. nov. is reported from the Hunghuayuan Formation (Lower Ordovician, Floian) of Guizhou Province in the South China Block and the Duwibong Formation (Middle Ordovician, Darriwilian) of the Taebaeksan Basin in mid-eastern Korea (North China Block). This species is the first representative of the genus found in both the North and South China blocks. Cystostroma primordia sp. nov. is characterized by the absence of denticles and distinctively smaller cyst plates (height 0.04-0.20 mm, length 0.09-0.39 mm) than any other known species of Cystostroma. The presence of C. primordia sp. nov. in Lower to Middle Ordovician strata of western Gondwana challenges the long-held view of the late Middle Ordovician emergence of Paleozoic stromatoporoids. The simple internal morphological features of this new species and its occurrence in the Lower Ordovician of South China strongly indicate that an Early Ordovician Cystostroma-type precursor from western Gondwana is located near the base of the stromatoporoid stock. This occurrence greatly preceded the late Middle Ordovician (late Darriwilian) stromatoporoid diversification in circum-equatorial regions worldwide.

• Korean Journal of Remote Sensing
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• v.19 no.5
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• pp.393-402
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• 2003

In times of the civil uses of commercialized high-resolution satellite imagery, applications of remote sensing have been widely extended to the new fields or the problem solving beyond traditional application domains. Transportation application of this sensor data, related to the automatic or semiautomatic road extraction, is regarded as one of the important issues in uses of remote sensing imagery. Related to these trends, this study focuses on automatic road extraction using Gradient Direction Profile Algorithm (GDPA) scheme, with IKONOS panchromatic imagery having 1 meter resolution. For this, the GDPA scheme and its main modules were reviewed with processing steps and implemented as a prototype software. Using the extracted bi-level image and ground truth coming from actual GIS layer, overall accuracy evaluation and ranking error-assessment were performed. As the processed results, road information can be automatically extracted; by the way, it is pointed out that some user-defined variables should be carefully determined in using high-resolution satellite imagery in the dense or low contrast areas. While, the GDPA method needs additional processing, because direct results using this method do not produce high overall accuracy or ranking value. The main advantage of the GDPA scheme on road features extraction can be noted as its performance and further applicability. This experiment study can be extended into practical application fields related to remote sensing.

• Journal of The Geomorphological Association of Korea
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• v.24 no.3
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• pp.13-25
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• 2017

This study is quantitative reconstruction of palaeo sea level records around Sinduk-ri, Gochang-Gun. 7 cores were collected from GC14 to GC18 in order to examine the entire sedimentary facies and reconstruct the sea level records. The cores were analysed by AMS, sedimentary facies, diatom and WA-pls. As a result of the diatom analysis, diatom zone were classified as No diatom zone, B1 zone, M zone and B2 zone. The result of WA-pls was that the sea level was about 1.5m lower than the present level around 6,000 BP and about 1m lower during last 5,000 BP. Thereafter, sea level rose to the present during the Mc sub-diatom zone period. Moreover, during the Md sub-diatom zone period, sea level was about 0.5m higher than the present.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.192-192
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• 2017

In this paper we showed the application of European Space Agency's C-band Sentinel-1 Synthetic Aperture Radar (SAR) imagery to identify land subsidence in a heavily groundwater pumping area. We used the repeat pass satellite interferometry method in combination with persistent scattering (PS) interferometric technique to generate and analyze twenty-eight interferograms for the period October 2014 to November 2016. The interferometry results show that land subsidence is more pronounced in the urban areas. Excessive groundwater pumping in the study area is believed to be the main reason for land subsidence. The results are compared with the subsidence rate measured by GPS as reported in other studies and with the mean change in total water storage field of GRACE solutions provided by the Jet Propulsion Laboratory (JPL), the German Research Centre for Geosciences (GFZ) and the Center for Space Research (CSR). The comparison shows persistently decreasing trends during the period of study. A strong reliance of the trend of land subsidence on the temporal decline in total water storage proposes that much of the land subsidence can be attributed to heavy pumping of the groundwater.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.3165-3181
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• 2019

Spherical videos, which are also called 360-degree videos, have become increasingly popular due to the rapid development of virtual reality technology. However, the large amount of data in such videos is a huge challenge for existing transmission system. To use the existing encode framework, it should be converted into a 2D image plane by using a specific projection format, e.g. the equi-rectangular projection (ERP) format. The existing high-efficiency video coding standard (HEVC) can effectively compress video content, but its enormous computational complexity makes the time spent on compressing high-frame-rate and high-resolution 360-degree videos disproportionate to the benefits of compression. Focusing on the ERP format characteristics of 360-degree videos, this work develops a fast decision algorithm for predicting the coding unit depth interval and adaptive mode decision for intra prediction mode. The algorithm makes full use of the video characteristics of the ERP format by dealing with pole and equatorial areas separately. It sets different reference blocks and determination conditions according to the degree of stretching, which can reduce the coding time while ensuring the quality. Compared with the original reference software HM-16.16, the proposed algorithm can reduce time consumption by 39.3% in the all-intra configuration, and the BD-rate increases by only 0.84%.

• Geosystem Engineering
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• v.21 no.6
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• pp.318-325
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• 2018

Eight tight sandstone reservoir samples from $He_8$ and $Shan_1$ Formations of the Sulige Gas field were selected to perform gas-water micro-displacement experiment based on authentic sandstone micro-model. The gas pressure-relief experiment was proposed for the first time to simulate the pressure change and gas-water percolation characteristics in the process of gas exploitation. The experiment results show that: (1) In the process of gas accumulation, the gas preferentially flows into the well-connected pores and throats with large radius, but rarely flows into the area without pores and throats. (2) Under sufficient gas drive, the water in pores and throats usually exists in the forms of 'thin water film', 'thick water film', and 'water column', but under insufficient gas drive, gas fails to flow into new pathways in time, so that the reservoirs with large pores and throats are high in water cut. (3) Under the same water saturation, the reservoirs with better petrophysical properties has higher gas recovery factor within unit time. Under the same petrophysical conditions, the reservoirs with lower water saturation show higher gas recovery factor within unit time. The higher the permeability, the stronger the liquid carrying capacity of reservoirs.