Quantification of free gas in the Kumano fore-arc basin detected from borehole physical properties: IODP NanTroSEIZE drilling Site C0009

Doan, Mai‐Linh; Conin, Marianne; Henry, Pierre; Wiersberg, Thomas; Boutt, D. F.; Buchs, David M.; Saffer, D. M.; McNeill, Lisa C.; Cukur, Deniz; Lin, Weiren

doi:10.1029/2010gc003284

Cited by 18 publications

(20 citation statements)

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“…A high gas flux would induce rapid gas hydrate formation in the hydrate stability zone above the BSR and lead to the coexistence of free gas and gas hydrate, primarily as a result of seawater being incorporated into gas hydrates (Suess et al 1999) and/or the presence of high salinity seawater (Milkov et al 2004). Doan et al (2011) analyzed sonic data obtained at Site C0009, ca. 20 km northeast of Site C0002, and suggested that biogenic gas produced from organic-rich layers in the deep Kumano Basin migrates upward and accumulates within tilted layers of coarser sediments, including migrating up-dip towards the southern or seaward edge of the Kumano Basin, in the vicinity of Site C0002.…”

Section: Discussionmentioning

confidence: 99%

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Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315, in the Kumano Basin, Nankai trough

et al. 2014

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The degree of gas hydrate saturation at Integrated Ocean Drilling Program (IODP) Site C0002 in the Kumano Basin, Nankai Trough, was estimated from loggingwhile-drilling logs and core samples obtained during IODP Expeditions 314 and 315. Sediment porosity data necessary for the calculation of saturation were obtained from both core samples and density logs. Two forms of the Archie equation ('quick-look' and 'standard') were used to calculate gas hydrate saturation from two types of electrical resistivity log data (ring resistivity and bit resistivity), and a three-phase Biot-type equation was used to calculate gas hydrate saturation from P-wave velocity log data. The gas hydrate saturation baseline calculated from both resistivity logs ranges from 0% to 35%, and that calculated from the P-wave velocity log ranges from 0% to 30%. High levels of gas hydrate saturation (>60%) are present as spikes in the ring resistivity log and correspond to the presence of gas hydrate concentrations within sandy layers. At several depths, saturation values obtained from P-wave velocity data are lower than those obtained from bit resistivity data; this discrepancy is related to the presence of free gas at these depths. Previous research has suggested that gas from deep levels in the Kumano Basin has migrated up-dip towards the southern and seaward edge of the basin near Site C0002. The high saturation values and presence of free gas at site C0002 suggest that a large gas flux is flowing to the southern and seaward edge of the basin from a deeper and/or more landward part of the Kumano Basin, with the southern edge of the Kumano Basin (the location of site C0002) being the main area of fluid accumulation.

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Section: Discussionmentioning

confidence: 99%

“…Doan et al (2011) determined that free gas is generated by organic-rich layers at IODP Site C0009 (Fig. 1), landward from the edge of the basin, and suggested that this free gas migrates upwards and accumulates within tilted layers of coarser sediments.…”

Section: Introductionmentioning

confidence: 99%

Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315, in the Kumano Basin, Nankai trough

et al. 2014

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“…[14] Saffer et al [2010] and Doan et al [2011] reported the segment of gas zones above 1285 mbsf. Low P-wave velocity is characterized in these sections.…”

Section: Estimation Of the Magnitude Of The Horizontal Principal Stressmentioning

confidence: 99%

Stress state estimation by geophysical logs in NanTroSEIZE Expedition 319‐Site C0009, Kumano Basin, southwest Japan

Kinoshita

Yukitoshi

2012

Geophysical Research Letters

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To understand the stress regime in the shallow portion of the Nankai Trough seismogenic zone, we carefully investigated the resistivity image logs at IODP Site C0009 that penetrated to 1600 meters below the sea floor (mbsf) in the central Kumano forearc basin. During the riser drilling, several downhole measurements were run including image logs, caliper and comprehensive geophysical logs sets. Borehole resistivity images obtained by a wireline‐logging tool were reprocessed in order to eliminate image artifacts generated by sticky tool movements, etc. The constraints on the possible magnitude and orientation of horizontal principal stresses are provided from the borehole images, rock strength, and logging data. The absence of borehole breakouts above 1285 mbsf represents a small difference (<10 MPa) between horizontal principal stresses and reflects the normal faulting and strike–slip faulting stress regimes. A stable, continuous breakout was observed in the resistivity image logs suggest that the stress state is in a strike–slip faulting and tending to reverse faulting regime below 1285 mbsf. The differential horizontal stress (up to 15 MPa) is significantly larger than in the shallow portion of the borehole (SHAMX ≫ Sv > Shmin).

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“…This package of lower basin sediments is very thin at C0002, but is significantly thicker in other regions more landward in the basin (refer to Table S1). Very high TOC content was found in the same sequence at C0009 (5.0 wt %) [57]. HARs are imaged across the organic rich sediment package, and are geophysical evidence for gas charge fluid delivery from the accretionary prism and deep basin sediments.…”

Section: Drilling Data Summarymentioning

confidence: 88%

“…Prior to subduction, these thermogenic gases may be transported up into basin sediments with deeply sourced fluids from the heavily fractured underlying accretionary prism. Hydrate saturations in the upper basin sediments were calculated by several groups using proxy measurements including Cl-freshening [59] and well-logs [57,[59][60][61]. Discrepancies in their assessments are related to their baseline assumptions.…”

Section: Drilling Data Summarymentioning

confidence: 99%

Gas-In-Place Estimate for Potential Gas Hydrate Concentrated Zone in the Kumano Basin, Nankai Trough Forearc, Japan

2017

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Methane hydrate concentrated zones (MHCZs) have become targets for energy exploration along continental margins worldwide. In 2013, exploratory drilling in the eastern Nankai Trough at Daini Atsumi Knoll confirmed that MHCZs tens of meters thick occur directly above bottom simulating reflections imaged in seismic data. This study uses 3-dimensional (3D) seismic and borehole data collected from the Kumano Basin offshore Japan to identify analogous MHCZs. Our survey region is located~100 km southwest of the Daini Atsumi Knoll, site of the first offshore gas hydrate production trial. Here we provide a detailed analysis of the gas hydrate system within our survey area of the Kumano forearc including: (1) the 3D spatial distribution of bottom simulating reflections; (2) a thickness map of potential MHCZs; and (3) a volumetric gas-in-place estimate for these MHCZs using constraints from our seismic interpretations as well as previously collected borehole data. There is evidence for two distinct zones of concentrated gas hydrate 10-90 m thick, and we estimate that the amount of gas-in-place potentially locked up in these MHCZs is 1.9-46.3 trillion cubic feet with a preferred estimate of 15.8 trillion cubic feet. Keywords: gas hydrates; Kumano Basin; bottom simulating reflections; methane hydrate exploration; 3D seismic interpretation; Nankai Trough IntroductionNatural gas hydrates (GH) are crystalline inclusion compounds that form within the pore space of marine sediments along continental margins worldwide. These hydrate deposits are stable at specific pressure-temperature relationships, host highly compressed gas molecules (most commonly methane), and are proposed to be the largest dynamic reservoir of organic carbon on this planet [1][2][3]. GHs have enticed global interest for several reasons including climate change and potential slope stability hazards, but primarily because these deposits could prove to be an unconventional energy resource [3,4]. At the exploration stage, it is important to develop systematic GH exploration methods that consider gas source, migration mechanisms into the hydrate stability field, zones of free gas, indicators of gas hydrate accumulation, and at least a first order volumetric gas-in-place estimate for apparent zones of concentrated hydrates [5,6].Seismic imaging is an important tool for identifying GH because both GH and free gas alter the physical properties of marine sediments, which will in turn affect the travel path and attenuation of the seismic wavelet [7][8][9]. Concentrated hydrate deposits tend to form at and just above the base of gas hydrate stability (BGHS). This results in a sharp contrast in mechanical properties at the phase boundary between GH saturated layers overlying a zone where free gas, water, and potentially non-cementing hydrate occupy the pore space [10]. This contrast in physical properties is expressed in seismic data as bottom simulating reflections (BSRs), and BSRs remain our strongest remotely sensed indicator to infer the presence of GH [11...

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Quantification of free gas in the Kumano fore-arc basin detected from borehole physical properties: IODP NanTroSEIZE drilling Site C0009

Cited by 18 publications

References 20 publications

Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315, in the Kumano Basin, Nankai trough

Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315, in the Kumano Basin, Nankai trough

Stress state estimation by geophysical logs in NanTroSEIZE Expedition 319‐Site C0009, Kumano Basin, southwest Japan

Gas-In-Place Estimate for Potential Gas Hydrate Concentrated Zone in the Kumano Basin, Nankai Trough Forearc, Japan

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