scholarly journals The differences between the measured heat flow and BSR heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

2018 ◽  
Vol 37 (2) ◽  
pp. 756-769 ◽  
Author(s):  
Miao Dong ◽  
Jian Zhang ◽  
Xing Xu ◽  
Shi-Guo Wu
Keyword(s):  
Heat Flow ◽  
Gas Hydrate ◽  
Northern South China Sea ◽  
Geothermal Gradient ◽  
Topographic Effects ◽  
Fluid Flux ◽  
Flow Measurements ◽  
Upward Migration ◽  
Bottom Simulating Reflector ◽  
The Impact

Temperature is an important factor that affects the stability of a gas hydrate. To investigate the geothermal characteristics in the gas hydrate drilling area, heat flow measurements were performed in the surrounding area of the SH2 well. The measured heat flow was compared with the bottom simulating reflector heat flow, which was calculated by using the depth of the bottom simulating reflector in the seismic data. Combined with the geological background of the Shenhu drilling area, we analyzed the reasons for the differences between the measured heat flow and the bottom simulating reflector heat flow. In addition to analyzing the differences caused by the calculation parameters, we calculated the 3-D topographic effects on the measured heat flow by using the finite element numerical simulation method. The results show that the measured heat flow was seriously affected by the topography and produced a −50–30% error in the study area. After terrain correction of the measured heat flow, we found that the data were greater than the bottom simulating reflector heat flow at almost all sites. Therefore, we considered the impact of fluid activity and calculated the relationship among the thickness of the gas hydrate stability zone, the fluid flux and the heat flow. The results show that when the base of the bottom simulating reflector was at a certain depth, the geothermal gradient increased with the increasing upward migration of the fluid flux. Therefore, when upward fluid migration is present, the measured heat flow in the seafloor sediments is greater than the heat flow in the deep layers. In general, we showed that the influences of the topography and fluid activity are the main factors leading to the inconsistency between the bottom simulating reflector heat flow and the measured heat flow in the Shenhu gas hydrate drilling area.

scholarly journals Heat Flow Measurements at the Danube Deep-Sea Fan, Western Black Sea

Geosciences ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 240
Author(s):  
Michael Riedel ◽  
Jörg Bialas ◽  
Heinrich Villinger ◽  
Thomas Pape ◽  
Matthias Haeckel ◽  
...  
Keyword(s):  
Heat Flow ◽  
Black Sea ◽  
Gas Hydrate ◽  
Deep Sea ◽  
Topographic Effects ◽  
Red Clay ◽  
Flow Measurements ◽  
Study Region ◽  
Late Pleistocene To Holocene ◽  
Sea Fan

Seafloor heat flow measurements are utilized to determine the geothermal regime of the Danube deep-sea fan in the western Black Sea and are presented in the larger context of regional gas hydrate occurrences. Heat flow data were collected across paleo-channels in water depths of 550–1460 m. Heat flow across levees ranges from 25 to 30 mW m−2 but is up to 65 mW m−2 on channel floors. Gravity coring reveals sediment layers typical of the western Black Sea, consisting of three late Pleistocene to Holocene units, notably red clay within the lowermost unit cored. Heat flow derived from the bottom-simulating reflector (BSR), assumed to represent the base of the gas hydrate stability zone (GHSZ), deviates from seafloor measurements. These discrepancies are linked either to fast sedimentation or slumping and associated variations in sediment physical properties. Topographic effects account of up to 50% of heat flow deviations from average values. Combined with climate-induced variations in seafloor temperature and sea-level since the last glacial maximum large uncertainties in the prediction of the base of the GHSZ remain. A regional representative heat flow value is ~30 mW m−2 for the study region but deviations from this value may be up to 100%.

The characteristics of heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

2016 ◽  
Vol 37 (4) ◽  
pp. 325-335 ◽  
Author(s):  
Xing Xu ◽  
Zhifeng Wan ◽  
Xianqing Wang ◽  
Yuefeng Sun ◽  
Bin Xia
Keyword(s):  
Heat Flow ◽  
South China Sea ◽  
South China ◽  
Gas Hydrate ◽  
Northern South China Sea ◽  
China Sea

A discussion concerning the floor of the northwest Indian Ocean - Heat flow in the northwest Indian Ocean and Red Sea

1966 ◽  
Vol 259 (1099) ◽  
pp. 271-278 ◽  
Keyword(s):  
Indian Ocean ◽  
Heat Flow ◽  
Red Sea ◽  
Deep Structure ◽  
Geothermal Gradient ◽  
Mean Value ◽  
Flow Measurements ◽  
Bottom Water Temperature ◽  
The Indian Ocean ◽  
Flow Through

Twenty-four measurements of the heat flow through the ocean floor were made in the Indian Ocean and three in the Red Sea. A critical analysis of the effects of fluctuations of bottom-water temperature on the geothermal gradient in the Red Sea shows that these fluctuations do not invalidate the measurements of heat flow. The mean value for the Gulf of Aden (this includes five previous measurements) is 3.89 + 0.49 /tcal cm -2 s -1 . This high value, combined with the shape of a profile across the Gulf, suggests a region of unusually high temperature at a depth of less than 10 km below the bottom. The seventeen heat flow measurements made by R.R.S. Discovery and R. V. Vema between the African coast and the Seychelles show little variation about a mean value of 1.17 /tcal cm -2 s -1 . The comparison of these observations and the deep structure, as determined by a series of seismic lines, shows a constant heat flow across the continental margin. The author is indebted to Mr R. Belderson of the National Institute of Oceanography for a brief description of the cores taken on the cruise.

Associated Interpretation of Sub-Bottom and Single-Channel Seismic Profiles from Shenhu Area in the North Slope of South China Sea - Characteristic of Gas Hydrate Sediment

2011 ◽  
Vol 217-218 ◽  
pp. 1430-1437
Author(s):  
Shou Jun Li ◽  
Feng You Chu ◽  
Yin Xia Fang ◽  
Zi Yin Wu
Keyword(s):  
South China Sea ◽  
South China ◽  
Gas Hydrate ◽  
Single Channel ◽  
Northern South China Sea ◽  
Seismic Profile ◽  
Seismic Profiles ◽  
Shenhu Area ◽  
Bottom Simulating Reflector ◽  
China Sea

Abstract：The study area of this paper is the slope of Shenhu Area in the northern South China Sea. We interpreted both sub-bottom and single-channel seismic profiles to describe the acoustic characteristic of gas hydrate sediment and to discuss the cause of its formation. We distinguished some abnormal physiognomy and geologic objects that are relative to gas hydrate in profiles. Protuberance, shallow fault, acoustic blank patch, partial enhanced reflection and acoustic blank zone were discovered in the legible sub-bottom profile. The shallow gassy belt locates under the seabed from 34 to 82 m. Contrasting the sub-bottom profile with the data of Chinese first gas hydrate expedition, we believed that the gas in the shallow gassy belt came from the decompounding of gas hydrate in deep stratum. Pockmark, seepage, fold and Bottom Simulating Reflector (BSR) were recognized in the single-channel seismic profile. The depth of BSR is slightly deeper than that of the samples of Chinese first gas hydrate expedition in the study area. We think the BSR in the seismic profile may be the bottom of gas hydrate. Based on the time-depth conversion, we plotted out Oligocene, early Miocene, middle Miocene and Pliocene in the seismic profile according to the sedimentary thickness, sedimentary rate and age of ODP site 1148 and set up the chronology of the gas hydrate sediment.

Occurrence of gas hydrate in the Chukchi plateau, Arctic

2020 ◽  
Author(s):  
Young Keun Jin ◽  
Seung-Goo Kang ◽  
Ugeun Jang ◽  
Sookwan Kim ◽  
Yeonjin Choi ◽  
...  
Keyword(s):  
Heat Flow ◽  
Gas Hydrate ◽  
Lower Boundary ◽  
Geothermal Gradient ◽  
The Arctic ◽  
Western Slope ◽  
Seismic Profiles ◽  
Arctic Seas ◽  
Geophysical Surveys ◽  
Chukchi Plateau

<p>The Arctic MArine Geoscience Expedition (AMAGE) program led by the Korea Polar Research Institute (KOPRI) is a multidisciplinary undertaking to investigate the geological environment and methane release phenomena in the Arctic seas. The icebreaking research vessel (IBRV) Araon has carried out three expeditions in the Chukchi Plateau (CP) and the East Siberian Seas in 2016, 2018 and 2019. In the first 2016 expedition, a chain of topographic mounds (with the height of several tens meters and the width of hundreds meters) was identified by subbottom profiler and multibeam bathymetric survey in the western continental slope of the CP. Gas hydrate samples were first retrieved in the Araon Mound-6 among the mound structures in the CP and ESS areas during the expedition. The detailed morphology and subsurface structures of the mounds were mapped from the subsequent expeditions in 2018 and 2019. More gas hydrate samples were obtained in the Araon Mound-3 and Araon Mound-6 in these expeditions. To examine gas hydrate occurrence conditions, we conducted geophysical surveys including seismic (sparker in 2018 and multi-channel in 2019) and heat flow methods during these expeditions. The seismic profiles obtained using two seismic methods show very well-developed bottom simulating reflectors (BSRs) which are widespread on the western slope of the study area. The BSR depths detected on the seismic profiles are well coincided with the depths of the lower boundary of the gas hydrate stability zone calculated from the geothermal gradient of heat flow measurement.</p><p>Arctic gas hydrates are considered to be vulnerable to the ongoing rapid Arctic warming. The AMAGE program will provide comprehensive understanding on poorly-known gas hydrate in the Arctic in the various research fields of geology, geophysics, geochemistry, biogeoscience, and oceanography.</p>

scholarly journals Model-Based Identification of the Base of the Gas Hydrate Stability Zone in Multichannel Reflection Seismic Data, Offshore Costa Rica

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
Romina Gehrmann ◽  
Christian Müller ◽  
Peter Schikowsky ◽  
Thomas Henke ◽  
Michael Schnabel ◽  
...  
Keyword(s):  
Costa Rica ◽  
Heat Flow ◽  
Gas Hydrate ◽  
Depth Range ◽  
Stability Zone ◽  
Amplitude Variation With Offset ◽  
Bottom Simulating Reflector ◽  
Thermal Anomalies ◽  
Reflection Seismic ◽  
Hydrate Stability

Along the pacific margin offshore Costa Rica the Bottom Simulating Reflector (BSR) shows a patchy occurrence in 2-D seismic reflection profiles. The reason for this can be either lack of free gas beneath parts of the gas hydrate stability zone (GHSZ) or poor seismic imaging. We compare far to near offset stacked common midpoint sections to reduce imaging ambiguity utilizing the amplitude variation with offset effect and thus successfully distinguish BSRs from regular sediment reflections. In combination with 1-D modeling of the base of the GHSZ we disqualify or qualify reflections in the predicted depth range as BSR. Additionally we calculate the heat flow and compare it with an analytical solution to detect thermal anomalies, for example, at the frontal prism. The higher confidence in BSR depths based on the far offset stacks and heat flow calculations allows further analyses on gas hydrate concentration estimates and tectonic evolution of the margin.

scholarly journals Gas origin linked to paleo BSR

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iván de la Cruz Vargas-Cordero ◽  
Lucia Villar-Muñoz ◽  
Umberta Tinivella ◽  
Michela Giustiniani ◽  
Nathan Bangs ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Geothermal Gradient ◽  
Last Deglaciation ◽  
Seismic Line ◽  
Central Chile ◽  
Free Gas ◽  
Bottom Simulating Reflector ◽  
South Central ◽  
Gas System ◽  
Central South

AbstractThe Central-South Chile margin is an excellent site to address the changes in the gas hydrate system since the last deglaciation associated with tectonic uplift and great earthquakes. However, the dynamic of the gas hydrate/free gas system along south central Chile is currently not well understood. From geophysical data and modeling analyses, we evaluate gas hydrate/free gas concentrations along a seismic line, derive geothermal gradients, and model past positions of the Bottom Simulating Reflector (BSR; until 13,000 years BP). The results reveal high hydrate/free gas concentrations and local geothermal gradient anomalies related to fluid migration through faults linked to seafloor mud volcanoes. The BSR-derived geothermal gradient, the base of free gas layers, BSR distribution and models of the paleo-BSR form a basis to evaluate the origin of the gas. If paleo-BSR coincides with the base of the free gas, the gas presence can be related to the gas hydrate dissociation due to climate change and geological evolution. Only if the base of free gas reflector is deeper than the paleo-BSR, a deeper gas supply can be invoked.

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