Gas hydrates in the Ulleung Basin, East Sea of Korea

Abstract

To develop gas hydrates as a potential energy source, geophysical surveys and geological studies of gas hydrates in the Ulleung Basin, East Sea off the east coast of Korea have been carried out since 1997. Bottom-simulating reflector (BSR), initially used indicator for the potential presence of gas hydrates was first identified on seismic data acquired in 1998. Based on the early results of preliminary R&D project, 12367 km of 2D multichannel reflection seismic lines, 38 piston cores, and multi-beam echo-sounder data were collected from 2000 to 2004. The cores showed high amounts of total organic carbon and high residual hydrocarbon gas levels. Gas composition and isotope ratios define it as of primarily biogenic origin. In addition to the BSRs that are widespread across the basin, numerous chimney structures were found in seismic data. These features indicate a high potential of the Ulleung Basin to host significant amounts of gas hydrate. Dedicated geophysical surveys, geological and experimental studies were carried out culminating in two deep drilling expeditions, completed in 2007 and 2010. Sediment coring (including pressure coring), and a comprehensive well log program complements the regional studies and were used for a resource assessment. Two targets for a future test-production are currently proposed: pore-filling gas hydrate in sand-dominated sediments and massive occurrences of gas hydrate within chimney-like structures. An environmental impact study has been launched to evaluate any potential risks to production.

Progress in Global Gas Hydrate Development and Production as a New Energy Resource

“…2D multichannel reflection seismic data, 38 piston cores, and multibeam echo-sounder data were acquired between 2000 and 2004. Laboratory analyses of cores yielded high total organic carbon contents and high levels of residual hydrocarbon gas (Ryu and Riedel, 2017). Besides the abundance of BSRs across the Ulleung Basin, the survey also resulted in the discovery of numerous gas chimneys.…”

“…Besides the abundance of BSRs across the Ulleung Basin, the survey also resulted in the discovery of numerous gas chimneys. The research vessel R/V TAMHAE II, enabled the acquisition of 700 km 2 of 3D seismic, high resolution compressed high intensity radar pulse, and echo-sounder data from 2005 to 2009 (Ryu and Riedel, 2017).…”

Analysis of short‐ and long‐term system response during gas production from a gas hydrate deposit at the UBGH2‐6 site of the Ulleung Basin in the Korean East Sea

“…[1][2][3][4][5] The water depth at the UBGH2-6 site (Figure 2) is 2157 m, with the top of the F I G U R E 1 Physiographic map of the Ulleung Basin [3] F I G U R E 2 Bathymetry, 2-D seismic track lines, 3-D survey area (blocked) and drilling sites during the UBGH1 and UBGH2 scientific (UBGHx: Ulleung Basin Gas Hydrates, x: number of the scientific expedition) expeditions [5] hydrate layer being at 140 mbsf under a relatively thin layer of mud. [4] The 12.7 m-thick (41.5 ft) system [2] we are investigating here extends over a 3 Â 4 km area and is characterized by the alternating layers of (a) clays (muds) that are nearly devoid of hydrates and (b) hydrate-rich sands depicted in Figure 3, which provides some basic data on the system geometry, the thickness of the various layers, the corresponding layer porosity ϕ, and the initial hydrate saturation S H . The base of the gas hydrate stability zone (BGHSZ) is 22.3 m below the base of the hydrate accumulation, that is, this is a thermodynamically stable system at an initial pressure of about 2.4 bars above the equilibrium pressure at the reservoir temperature.…”

“…It uses the most recent information on the geology, stratigraphy, flow, and geomechanics of the sediments at the UBGH2-6 site (UBGH2, Ulleung Basin Gas Hydrates 2; 2 is the number of the scientific expedition), as gleaned from core analyses and advanced geophysical surveys referenced in that study, and later expanded via additional field data and site characterization. [2] The objective of this work is to quantify by means of numerical simulation the response of the hydrate accumulation at the UBGH2-6 site during (a) a short-term field test (14-day long) aiming to determine the technical feasibility of gas production through depressurization-induced dissociation and (b) a longer-term production regime that may continue to the point of hydrate exhaustion and/or reservoir abandonment. The study, the main focus of which is a proposed short-term test, estimates the baseline production performance of the accumulation and then estimates the sensitivity of production to several important parameters.…”

Preliminary results of integrated oceanographic and geophysical observations in the profile of Peter the Great Bay – Tsushima Strait (the Sea of Japan, October 2019)

“…В рейсе LV84 отмечены аномально высокие значения метана в приповерхностной воде Цусимской котловины -9,9 нмоль/л. Известно, что в данном регионе были обнаружены газогидраты [7].…”