Seismic chimneys in the Southern Viking Graben – Implications for palaeo fluid migration and overpressure evolution

Karstens, Jens; Berndt, Christian

doi:10.1016/j.epsl.2014.12.017

Cited by 86 publications

(74 citation statements)

References 48 publications

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“…RMS amplitude taken between the uppermost SS2 reflector, to the base of the conical feature (Fig. 10b,c;Krabbenhoeft et al, 2013;Karstens & Berndt, 2015). There is a small rim-syncline feature around the northern flank of the conical feature (Fig.…”

Section: Conical Featurementioning

confidence: 99%

Paleo‐fluid expulsion and contouritic drift formation on the Chatham Rise, New Zealand

et al. 2017

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The Chatham Rise is located offshore of New Zealand's South Island. Vast areas of the Chatham Rise are covered in circular to elliptical seafloor depressions that appear to be forming through a bathymetrically controlled mechanism, as seafloor depressions 2-5 km in diameter are found in water depths of 800-1100 m. High-resolution P-Cable 3D seismic data were acquired in 2013 across one of these depressions. The seafloor depression is interpreted as a mounded contourite. Our data reveal several smaller buried depressions (<20-650 m diameter) beneath the mounded contourite that we interpret as paleo-pockmarks. These pockmarks are underlain by a complex polygonal fault system that deforms the strata and an unusual conical feature results. We interpret the conical feature as a sediment remobilization structure based on the presence of stratified reflections within the feature, RMS amplitude values and lack of velocity anomaly that would indicate a nonsedimentary origin. The sediment remobilization structure, polygonal faults and paleo-depressions are the indicators of the past subsurface fluid flow. We hypothesize that the pockmarks provided the necessary topographic roughness for the formation of the mounded contourites thus linking fluid expulsion and the deposition of contouritic drifts.

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Section: Conical Featurementioning

confidence: 99%

Paleo‐fluid expulsion and contouritic drift formation on the Chatham Rise, New Zealand

et al. 2017

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“…The North Sea is affected by focused flow of hydrocarbons from deep thermogenic sources, strongly mixed with microbially formed shallow methane (Chand et al, ; Karstens & Berndt, ). Three decades of extensive surveying and seafloor mapping in the Witch Ground Basin has revealed abundant “normal” pockmarks and multiple “unusually large” pockmarks.…”

Section: Regional Settingmentioning

confidence: 99%

Pockmarks in the Witch Ground Basin, Central North Sea

Böttner

Berndt

Reinardy

et al. 2019

Geochem Geophys Geosyst

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Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. Quantitative estimates for methane release from marine sediments are scarce, and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios. Here, we use 2‐D and 3‐D seismic reflection, multibeam bathymetric, geochemical, and sedimentological data to (I) map and describe pockmarks in the Witch Ground Basin (central North Sea), (II) characterize associated sedimentological and fluid migration structures, and (III) analyze the related methane release. More than 1,500 pockmarks of two distinct morphological classes spread over an area of 225 km2. The two classes form independently from another and are corresponding to at least two different sources of fluids. Class 1 pockmarks are large in size (>6 m deep, >250 m long, and >75 m wide), show active venting, and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources. Class 2 pockmarks, which comprise 99.5% of all pockmarks, are smaller (0.9–3.1 m deep, 26–140 m long, and 14–57 m wide) and are limited to the soft, fine‐grained sediments of the Witch Ground Formation and possibly sourced by compaction‐related dewatering. Buried pockmarks within the Witch Ground Formation document distinct phases of pockmark formation, likely triggered by external forces related to environmental changes after deglaciation. Thus, greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present‐day fluxes but require an analysis of the pockmark forming processes through geological time.

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“…ERs that represented the charging of hydrocarbons (free gas trap) are observed around or on the structural highs of those diapiric faults and cracks, which demonstrate that the deep hydrocarbons had migrated through diapiric and associated structures (Figure ; Sun, Wu, Cartwright, & Dong, ; Wang, Collett, et al, ). Furthermore, the gas chimney itself is an efficient migration pathway for natural gas (Cartwright et al, ; Horozal et al, ; Kang et al, ; Karstens & Berndt, ; Petersen et al, ; Sun, Wu, Cartwright, & Dong, ; Sun, Wu, Dong, et al, ). The direct evidence is the pull‐down of events that can be found at the edges or inside the gas chimneys, which resulted from a decreased velocity and increased travel time of the seismic wave in the gas‐charged formations (Karstens & Berndt, ; Scholl et al, ; Wu et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the gas chimney itself is an efficient migration pathway for natural gas (Cartwright et al, ; Horozal et al, ; Kang et al, ; Karstens & Berndt, ; Petersen et al, ; Sun, Wu, Cartwright, & Dong, ; Sun, Wu, Dong, et al, ). The direct evidence is the pull‐down of events that can be found at the edges or inside the gas chimneys, which resulted from a decreased velocity and increased travel time of the seismic wave in the gas‐charged formations (Karstens & Berndt, ; Scholl et al, ; Wu et al, ). Based on the analysis of the instantaneous frequency of the seismic fuzzy zones, we find that the gas chimney zones are characterized by low frequency, distinctly different from nearby reflections, indicating a large amount of the high frequency of reflections had been absorbed (Figure c; Sun, Wu, Dong, et al, ; Taylor, Dillon, & Pecher, ).…”

Section: Discussionmentioning

confidence: 99%

Distribution and characteristics of mud diapirs, gas chimneys, and bottom simulating reflectors associated with hydrocarbon migration and gas hydrate accumulation in the Qiongdongnan Basin, northern slope of the South China Sea

Zhang

Gong

et al. 2018

Geological Journal

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A comprehensive analysis on high‐resolution seismic data and the geological characteristics of the Qiongdongnan Basin (QDNB) in the northern South China Sea reveals multiple seismic evidence indicative of hydrocarbon migration and gas hydrate accumulation, including mud diapirs, gas chimneys, bottom simulating reflectors (BSRs), acoustic blanking, enhanced reflections, V‐AMP structures, elevated stacking velocity of sediments, and seafloor expressions. Mud diapirs and gas chimneys, which are characterized by acoustic turbidity, fuzziness, and blanking reflections on seismic profiles, with a diversity of structures and scales, are widespread and concentrated in the centres of sags and the transitional zones between sags and uplifts. Five BSR regions, with a total area of approximately 11,000 km2, have been delineated in the QDNB. They have high or medium‐high continuity amplitudes with overlying acoustic blanking on seismic profiles, indicating the occurrence of gas hydrate. Distinct fluid seepage phenomena are common below the BSRs, demonstrating that abundant free gas has migrated and accumulated beneath the gas hydrate. The distribution of BSRs and the developed zones of mud diapirs and gas chimneys presents a spatial superposition feature, and the BSRs are usually located on top of or within the structural highs of the mud diapirs and gas chimneys, indicating a close relationship between them. Mud diapirs, gas chimneys, and associated faults are efficient pathways for migrating hydrocarbons, through which the mature to highly mature thermogenic gas of the Palaeogene strata and the biogenic gas of the Neogene sediments migrate to the gas hydrate stability zones and form gas hydrate. Gas hydrate samples were recovered from the gas chimney area during the remote operated vehicle (ROV) investigation in deepwater QDNB in 2015. Based on the seismic interpretation and geochemical results, we propose two models of gas hydrate accumulation in the deepwater area of the QDNB: (a) near source biogenic gas hydrate with self‐generation and self‐accumulation, and (b) distal source thermogenic gas hydrate with lower generation and upper accumulation. We believe that the areas with a fine spatial coupling configuration between the mud diapirs, gas chimneys, and BSRs are favourable exploration targets for gas hydrate in the QDNB.

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Seismic chimneys in the Southern Viking Graben – Implications for palaeo fluid migration and overpressure evolution

Cited by 86 publications

References 48 publications

Paleo‐fluid expulsion and contouritic drift formation on the Chatham Rise, New Zealand

Paleo‐fluid expulsion and contouritic drift formation on the Chatham Rise, New Zealand

Pockmarks in the Witch Ground Basin, Central North Sea

Distribution and characteristics of mud diapirs, gas chimneys, and bottom simulating reflectors associated with hydrocarbon migration and gas hydrate accumulation in the Qiongdongnan Basin, northern slope of the South China Sea

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