• Journal of Ocean Engineering and Technology
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• v.25 no.3
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• pp.90-95
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• 2011

On April 20, 2010, a well control event allowed hydrocarbon (oil and gas) to escape from the Macondo well onto Deepwater Horizon (DWH), resulting in an exploration and fire on the rig. While 17 people were injured, 11 others lost their lives. The fire continued for 36 hours until the rig sank. Hydrocarbons continued to flow out from the reservoir through the well bore and blowout preventer (BOP) for 87 days, causing an unprecedented oil spill. Beyond Petroleum (BP) and the US federal government tried various methods to prevent the oil spill and to capture the spilled oil. The corresponding responses were very challenging due to the scale, intensity, and duration of the incident that occurred under extreme conditions in terms of pressure, temperature, and amount of flow. On July 15, a capping stack, which is another BOP on top of the existing BOP, was successfully installed, and the oil spill was stopped. After several tests and subsea responses, the well was permanently sealed by a relief well and a bottom kill on September 19. This paper analyzes the subsea responses and engineering efforts to capture the oil, stop the leaking, and kill the subsea well. During the investigation and analysis of subsea responses, information was collected and data bases were established for future accident prevention and the development of subsea engineering.

• Journal of the Korean Geophysical Society
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• v.5 no.2
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• pp.75-86
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• 2002

A TSP(Tunnel Seismic Prediction) survey which is modified VSP(Vertical Seismic Profiling) survey applied in tunnel was carried out at Pyongtaek and Incheon liquefied petroleum gas(LPG) storage cavern during excavation. The TSP survey in Pyongtaek LPG storage cavern which is located below Namyangho was performed to confirm the location and orientation of the fault detected at pre-investigation stage. The TSP survey was carried out in access tunnel, construction tunnel, and watercurtain tunnel to characterize 3 dimensional figure of the fault. The results of TSP survey are compared four in vestigation boreholes drilled in shelter of access tunnel. The fault was also detected by borehole survey and the location was coincided with the result of TSP survey. Depending on the result of TSP survey and core logging, the design such as cavern layout and length was changed. Another TSP survey was performed in Incheon LPG storage cavern which is located below sea. Because of poor geological information at pre-investigation stage and suffering from heavy leakage of groundwater, the TSP survey to detect fracture zone was carried out. The support and grouting design was reflected by the result of TSP survey.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.417-426
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• 2006

Data acquisition is as important as data processing and interpretation in the field of marine geophysical exploration. Marine geophysicist, however, may not have enough information in this field because data acquisition method has been mainly developed by the commercial companies manufacturing the equipment. Therefore, the purpose of this paper is to introduce the general data acquisition method and information to help to construct the systematic and effective survey plan. When a survey plan is set up, the most important thing is to select the seismic equipment based on required penetration depth and resolution, and then construct the survey line intervals. Although a line interval varies from the research purposes, it should be narrower than the expected subsurface structures. Also, if 100% coverage of multibeam data is required, line intervals need to be adjusted based on the equipment characteristics. In case of merging with the preexisting dataset like bathymetry, gravity and magnetic, cross-over errors occurred at the each cross point should be removed to avoid any kinds of misinterpretation.

• Journal of the Mineralogical Society of Korea
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• v.18 no.2
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• pp.73-81
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• 2005

Mineralogical and chemical examinations were performed on chlorite-smectite mixed layer minerals that occur in the sandstones from a petroleum exploration well in the southern part of the Ulleung Basin. X-ray diffraction and chemical analyses show that the chlorite-smectite mixed layer mineral is tosudite, a 1 : 1 R1 ordered interstratification of chlorite and smectite with an overall dioctahedral character. This mineral is almost the same as the tosudite reported from hydrothermally-altered regions, which is rich in Li. This fact indicates that the tosudite area may be affected by hydrothermal events, because the studied well is located in the tectonically-deformed area, in which lots of trust faults and folds are present. In these respects, the formation of tosudite is probably due to the variable effect of hydrothermal fluids from the deeper part of the area.

• Journal of the Korean Geophysical Society
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• v.8 no.4
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• pp.187-194
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• 2005

As a study of Arctic marine survey project, Side-scan sonar survey was carried out in the Pechora Sea belonging to the southeaster part of Barents Sea. The study area is a shallow sea 11 m-16 m deep with recent sediments of rich organic carbon. Side-scan sonar profiles show large-scale marine plant communities 2-3 m wide covering the southeastern area. A lot of lineaments are traced on the seafloor in the central and northern area. The major trends of the lineaments are 220°and 290°(WSW-ENE and WNW-ESE). This trends is thought to be a main path of icebergs. Pockmarks on the seafloor are locally distributed in the area, which are formed by fluid and/or gas discharge. These would be related with petroleum/gas system well developed around the study area. Dut to weak appearances and limited distribution of the pockmarks, more detailed studies are necessary to examine their nature and structure.

• Geomechanics and Engineering
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• v.36 no.2
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• pp.183-204
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• 2024

In current investigation, a novel beam finite element model is formulated to analyze the buckling and free vibration responses of functionally graded porous beams resting on Winkler-Pasternak elastic foundations. The novelty lies in the formulation of a simplified finite element model with only three degrees of freedom per node, integrating both C⁰ and C¹ continuity requirements according to Lagrange and Hermite interpolations, respectively, in isoparametric coordinate while emphasizing the impact of z-coordinate-dependent porosity on vibration and buckling responses. The proposed model has been validated and demonstrating high accuracy when compared to previously published solutions. A detailed parametric examination is performed, highlighting the influence of porosity distribution, foundation parameters, slenderness ratio, and boundary conditions. Unlike existing numerical techniques, the proposed element achieves a high rate of convergence with reduced computational complexity. Additionally, the model's adaptability to various mechanical problems and structural geometries is showcased through the numerical evaluation of elastic foundations, with results in strong agreement with the theoretical formulation. In light of the findings, porosity significantly affects the mechanical integrity of FGP beams on elastic foundations, with the advanced beam element offering a stable, efficient model for future research and this in-depth investigation enriches porous structure simulations in a field with limited current research, necessitating additional exploration and investigation.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.50-59
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• 2006

The risk of fault reactivation in the Gippsland Basin was calculated using the FAST (Fault Analysis Seal Technology) technique, which determines fault reactivation risk by estimating the increase in pore pressure required to cause reactivation within the present-day stress field. The stress regime in the Gippsland Basin is on the boundary between strike-slip and reverse faulting: maximum horizontal stress $({\sim}\;40.5\;Mpa/km)$ > vertical stress (21 Mpa/km) ${\sim}$ minimum horizontal stress (20 MPa/km). Pore pressure is hydrostatic above the Campanian Volcanics of the Golden Beach Subgroup. The NW-SE maximum horizontal stress orientation $(139^{\circ}N)$ determined herein is broadly consistent with previous estimates, and verifies a NW-SE maximum horizontal stress orientation in the Gippsland Basin. Fault reactivation risk in the Gippsland Basin was calculated using two fault strength scenarios; cohesionless faults $(C=0;{\mu}=0.65)$ and healed faults $(C=5.4;\;{\mu}=0.78)$. The orientations of faults with relatively high and relatively low reactivation potential are almost identical for healed and cohesionless fault strength scenarios. High-angle faults striking NE-SW are unlikely to reactivate in the current stress regime. High-angle faults oriented SSE-NNW and ENE-WSW have the highest fault reactivation risk. Additionally, low-angle faults (thrust faults) striking NE-SW have a relatively high risk of reactivation. The highest reactivation risk for optimally oriented faults corresponds to an estimated pore pressure increase (Delta-P) of 3.8 MPa $({\sim}548\;psi)$ for cohesionless faults and 15.6 MPa $({\sim}2262\;psi)$ for healed faults. The absolute values of pore pressure increase obtained from fault reactivation analysis presented in this paper are subject to large errors because of uncertainties in the geomechanical model (in situ stress and rock strength data). In particular, the maximum horizontal stress magnitude and fault strength data are poorly constrained. Therefore, fault reactivation analysis cannot be used to directly measure the maximum allowable pore pressure increase within a reservoir. We argue that fault reactivation analysis of this type can only be used for assessing the relative risk of fault reactivation and not to determine the maximum allowable pore pressure increase a fault can withstand prior to reactivation.

• Geophysics and Geophysical Exploration
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• v.21 no.3
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• pp.171-182
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• 2018

We performed the seismic field data processing using an open-source software (Madagascar) to verify if it is applicable to processing of field data, which has low signal-to-noise ratio and high uncertainties in velocities. The Madagascar, based on Python, is usually supposed to be better in the development of processing technologies due to its capabilities of multidimensional data analysis and reproducibility. However, this open-source software has not been widely used so far for field data processing because of complicated interfaces and data structure system. To verify the effectiveness of the Madagascar software on field data, we applied it to a typical seismic data processing flow including data loading, geometry build-up, F-K filter, predictive deconvolution, velocity analysis, normal moveout correction, stack, and migration. The field data for the test were acquired in Gunsan Basin, Yellow Sea using a streamer consisting of 480 channels and 4 arrays of air-guns. The results at all processing step are compared with those processed with Landmark's ProMAX (SeisSpace R5000) which is a commercial processing software. Madagascar shows relatively high efficiencies in data IO and management as well as reproducibility. Additionally, it shows quick and exact calculations in some automated procedures such as stacking velocity analysis. There were no remarkable differences in the results after applying the signal enhancement flows of both software. For the deeper part of the substructure image, however, the commercial software shows better results than the open-source software. This is simply because the commercial software has various flows for de-multiple and provides interactive processing environments for delicate processing works compared to Madagascar. Considering that many researchers around the world are developing various data processing algorithms for Madagascar, we can expect that the open-source software such as Madagascar can be widely used for commercial-level processing with the strength of expandability, cost effectiveness and reproducibility.

• The Korean Journal of Petroleum Geology
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• v.4 no.1_2 s.5
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• pp.27-39
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• 1996

In the Cretaceous, the Gulf Coast Basin evolved as a marginal sag basin. Thick clastic and carbonate sequences cover the disturbed and diapirically deformed salt layer. In the Cretaceous the salinities of the Gulf Coast Basin probably matched the Holocene Persian Gulf, as is evidenced by the widespread development of supratidal anhydrite. The major Lower Cretaceous reservoir formations are the Cotton Valley, Hosston, Travis Peak siliciclastics, and Sligo, Trinity (Pine Island, Pearsall, Glen Rose), Edwards, Georgetown/Buda carbonates. Source rocks are down-dip offshore marine shales and marls, and seals are either up-dip shales, dense limestones, or evaporites. During this period, the entire Gulf Basin was a shallow sea which to the end of Cretaceous had been rimmed to the southwest by shallow marine carbonates while fine-grained terrigengus clastics were deposited on the northern and western margins of the basin. The main Upper Cretaceous reservoir groups of the Gulf Coast, which were deposited in the period of a major sea level .rise with the resulting deep water conditions, are Woodbinefruscaloosa sands, Austin chalk and carbonates, Taylor and Navarro sandstones. Source rocks are down-dip offshore shales and seals are up-dip shales. Major trap types of the Lower and Upper Cretaceous include salt-related anticlines from low relief pillows to complex salt diapirs. Growth fault structures with rollover anticlines on downthrown fault blocks are significant Gulf Coast traps. Permeability barriers, up-dip pinch-out sand bodies, and unconformity truncations also play a key role in oil exploration from the Cretaceous Gulf Coast reservoirs. The sedimentary sequences of the major Cretaceous reseuoir rocks are a good match to the regressional phases on the global sea level cuwe, suggesting that the Cretaceous Gulf Coast sedimentary stratigraphy relatively well reflects a response to eustatic sea level change throughout its history. Thus, of the three main factors controlling sedimentation (tectonic subsidence, sediment input, and eustatic sea level change) in the Gulf Coast Basin, sea-level ranks first in the period.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.165-176
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• 2005

Natural gas in deep sediment may occur in three phases based on the physical and chemical conditions. If the concentration of gas in pore water is less than the solubility, gas is dissolved. If the concentration of gas is greater than its solubility (water is saturated or supersaturated with gas), gas occurs as a fee gas below the gas hydrate stability Lone (GHSZ) and is present as solid hydrate within the GHSZ. The knowledge of gas concentration in deep sediment appears critical to determine the phase of natural gases and to understand the formation and distribution of gas hydrate. However, reliable data on gas concentration are usually available only from the upper section of marine sediment by the headspace gas technique, which is widely used for sampling of gases from the sediments. The headspace gas technique represents only a fraction of gases present in situ because sediments release most of the gases during recovery and sampling. The PCS (Pressure Core Sampler) is a downhole tool developed to recover a nominal $1{\cal}m$ long, $4.32{\cal}cm$ diameter core containing $1,465cm^3$ of sediment, pore water and gas at in situ pressure up to 68.9 MPa. During Leg 204, the PCS was deployed at 6 Sites. In situ methane gas concentration and distribution of gas hydrate was measured by using PCS tool. Characteristics of methane concentration and distribution is different from site to site. Distribution of gas hydrate in the study area is closely related to characteristics of in situ gas concentration measured by PCS.