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Kalachand Sain - One of the best experts on this subject based on the ideXlab platform.
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Seismic attributes for characterizing gas hydrates: a study from the Mahanadi offshore, India
Marine Geophysical Research, 2019Co-Authors: Jitender Kumar, Kalachand Sain, K. P. ArunAbstract:Seismic attributes have become successful in illuminating subsurface features and are widely used for identifying hydrocarbon reservoirs. The present work delivers case study carried out in the Mahanadi offshore basin lying in the eastern margin of India to delineate gas hydrates bearing zones using high resolution 2D seismic data. The presence of gas hydrates is identified by a bottom simulating Reflector (BSR) on seismic section based on its characteristic features. Seismic attributes are computed to ascertain whether the BSR is related to gas hydrates. The data is conditioned using several post-stack processing steps such as detailed and background steering. The conditioning begins by steering of seismic data, which stores dip and azimuth information at every sample location. The Original seismic data is then filtered using a statistical filter to generate the dip-steered median filter data for extracting the instantaneous amplitude, instantaneous phase, instantaneous frequency, RMS amplitude and sweetness attributes. These are then used in demarcating the zones of gas hydrates or free gas occurrences. The low amplitude, high frequency and low sweetness attributes characterize the presence of gas hydrates. Whereas, free gas zones are characterized by bright amplitudes associated with low frequency and high sweetness below the BSR.
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Seismic attenuation for characterization of gas hydrate reservoir in Krishna-Godavari basin, eastern Indian margin
Journal of the Geological Society of India, 2017Co-Authors: Veligeti Jyothi, Kalachand Sain, Vivekanand Pandey, Ajoy K. BhaumikAbstract:Gas hydrates have received global attention as a possible alternative non-conventional energy resource. Hence, the detection, characterization and quantification of gas hydrates are very important for evaluating the resource potential. Presence of gas hydrates in sediments above the bottom simulating Reflector or BSR is associated with low attenuation or high quality factor (Q), whereas, free gas bearing sediments below the BSR exhibit high attenuation or low seismic Q. Here the logarithm spectral ratio (LSR) method is applied to marine seismic reflection data along two cross lines (18 and 46) in the Krishna-Godavari (KG) basin in eastern Indian margin, where gas hydrates have already been established by drilling/coring. The interval Qs is calculated for three sedimentary layers (A, B, and C) bounded by the seafloor, BSR, one Reflector above and another Reflector below the BSR at some common depth points (CDPs) to study the attenuation characteristics of sediments across the BSR. The estimated average interval Q (160) for the hydrate bearing sediments (layer B) is much higher than the average interval Q (80) for both the loose clayey sediments (Layer A) and underlying free gas saturated sediments (layer C). This demonstrates that estimation of seismic quality factor Q can be used for characterization of gas hydrate reservoir.
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Characteristics of Bottom-Simulating Reflectors for Hydrate-filled fractured sediments in Krishna–Godavari basin, eastern Indian margin
Journal of Petroleum Science and Engineering, 2014Co-Authors: Jiliang Wang, Kalachand Sain, Xiujuan Wang, N. SatyavaniAbstract:The Bottom-Simulating Reflector (BSR) is weak and patchy on the seismic section in the Krishna-Godavari basin, eastern Indian margin, where massive gas-hydrates have been recovered at Site 10 of the Indian National Gas-hydrates Program Expedition 01 (NGHP-01). The depth of the BSR near this site is around 160 m below the sea floor (mbsf). The average reflection coefficient from the BSR is -0.06, significantly smaller than the common global values of -0.1 to -0.2. The BSR shows a strong lateral variation in amplitudes along the seismic line due to the presence of faults. The methane solubility is modeled using a theoretical model of the gas-hydrates system, and methane concentrations from the pressure core show that the distribution of free gas below BSR is not uniform. A combination of synthetic seismogram analysis and rock physics modeling leads to the conclusion that weak and patchy BSRs are primarily caused by lateral discontinuities induced by the gas-filled fractures below BSRs. The free gas zone is thin and it shows segmented characteristics on the seismic section and acoustic impedance profile that we inverted. Fault zones increase the permeability and therefore trap gas in associated fractures that can scatter seismic energy and create low velocity zones. (C) 2014 Elsevier B.V. All rights reserved.
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2-D velocity structure in Kerala-Konkan basin using traveltime inversion of seismic data
Journal of the Geological Society of India, 2012Co-Authors: Praveen Kumar Singh, Kalachand SainAbstract:The existence of gas-hydrates in marine sediments increases the seismic velocity, whereas even a small amount of underlying free-gas reduces the velocity considerably. The change in velocities against the background (without gas-hydrates and free-gas) velocity can be used for identification and assessment of gas-hydrates. Traveltime inversion of identifiable reflections from large offset multi channel seismic (MCS) experiment is an effective method to derive the 2-D velocity structure in an area. We apply this method along a seismic line in the Kerala-Konkan (KK) offshore basin for delineating the gas-hydrates and free-gas bearing sediments across a bottom simulating Reflector (BSR). The result reveals a four layer 2-D shallow velocity model with the topmost sedimentary layer having velocity of 1,680–1,740 m/s and thickness of 140–190 m. The velocity of the second layer of uniform thickness (110 m) varies from 1,890 to 1,950 m/s. The third layer, exhibiting higher velocity of 2,100–2,180 m/s, is interpreted as the gas-hydrates bearing sediment, the thickness of which is estimated as 100 to 150 m. The underlying sedimentary layer shows a reduction in seismic velocity between 1,620 to 1,720 m/s. This low-velocity layer with 160–200 m thickness may be due to the presence of free-gas below the gas-hydrates layer.
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Seismic quality factors across a bottom simulating Reflector in the Makran Accretionary Prism, Arabian Sea
Marine and Petroleum Geology, 2011Co-Authors: Kalachand Sain, Anoop Kumar SinghAbstract:The hydrate-bearing sediments above the bottom simulating Reflector (BSR) are associated with low attenuation or high quality factor (Q), whereas underlying gas-bearing sediments exhibit high attenuation. Hence, estimation of Q can be important for qualifying whether a BSR is related to gas hydrates and free-gas. This property is also useful for identifying gas hydrates where detection of BSR is dubious. Here, we calculate the interval Q for three submarine sedimentary layers bounded by seafloor, BSR, one Reflector above and another Reflector below the BSR at three locations with moderate, strong and no BSR along a seismic line in the Makran accretionary prism, Arabian Sea for studying attenuation (Q � 1 ) characteristics of sediments. Interval Q for hydrate-bearing sediments (layer B) above the BSR are estimated as 191 � 11, 223 � 12, and 117 � 5, whereas interval Q for the underlying gas-bearing sediments (layer C) are calculated as 112 � 7, 107 � 8 and 124 � 11 at moderate, strong and no BSR locations, respectively. The large variation in Q is observed at strong BSR. Thus Q can be used for ascertaining whether the observed BSR is due to gas hydrates, and for identifying gas hydrates at places where detection of BSR is rather doubtful. Interval Q of 98 � 4, 108 � 5, and 102 � 5, respectively, at moderate, strong and no BSR locations for the layer immediately beneath the seafloor (layer A) show almost uniform attenuation.
Hervé Nouzé - One of the best experts on this subject based on the ideXlab platform.
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Geophysical characterization of bottom simulating Reflectors in the Fairway Basin (off New Caledonia, Southwest Pacific), based on high resolution seismic profiles and heat flow data
Marine Geology, 2009Co-Authors: Hervé Nouzé, Jean-paul Foucher, Emmanuel Cosquer, Julien Collot, Frauke Klingelhoefer, Yves Lafoy, Louis GéliAbstract:High-resolution reflection and refraction seismic data were collected in 2004 to investigate, in further detail than allowed by pre-existing low resolution seismic data, the nature of a Bottom Simulating Reflector (BSR) that extends over a broad area of the Fairway Basin, a rifted, continental structure located on the eastern flank of the Lord Howe Rise, to the southwest of New Caledonia. Two main Reflectors are documented: the shallower (RN) mimics the seafloor and has a negative polarity while the deeper (RP) does not always mimic the seafloor and has a positive polarity. Using the existing regional seismic lines, we can show that Reflector RN can be continuously followed up to DSDP 208 drill hole site. Reflector RP is discontinuous and cannot be traced to DSDP 208. Based on DSDP 208 stratigraphic data, Reflector RN is assigned to the Eocene/Oligocene regional unconformity; Reflector RP is interpreted in terms of a diagenetic BSR, likely related to an Opal-A/Opal-CT transition front. Heat flow data collected in 2006 suggest that Reflector RP lies too deep to be related to methane hydrates, strengthening our interpretation that RP is of diagenetic origin.
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Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège)
Comptes Rendus Geoscience, 2004Co-Authors: Hervé Nouzé, Isabelle Contrucci, Jean-paul Foucher, Bruno Marsset, Yannick Thomas, Estelle Thereau, Alain Normand, Eliane Le Drezen, Stéphane Didailler, Jean-pierre RegnaultAbstract:The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroit aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating Reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area. Les glissements de Storegga, au large de la Norvege, sont les plus grands glissements connus sur une pente continentale. Lors de la campagne Hydratech sur le N/O Le Suroit, un leve geophysique a haute resolution d'un secteur du flanc nord des glissements a ete effectue. Ce leve permet d'imager en detail l'extension et les proprietes du Bottom Simulating Reflector (BSR), les structures d'echappement de fluides et les deformations sedimentaires. La combinaison des differentes donnees acquises ainsi que leur qualite permettent de mieux comprendre les interactions encore mal contraintes entre fluides, hydrates de gaz et glissements sur la zone d'etude.
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Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège) First results of a geophysical survey on the northern flank of the Storegga slides (Norway).
2004Co-Authors: Hervé Nouzé, Isabelle Contrucci, Jean-paul Foucher, Bruno Marsset, Yannick Thomas, Alain Normand, Eliane Le Drezen, Stéphane Didailler, Jean-pierre RegnaultAbstract:The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroit aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating Reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area.
Satish C. Singh - One of the best experts on this subject based on the ideXlab platform.
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A Double Gas‐Hydrate Related Bottom Simulating Reflector at the Norwegian Continental Margin
Annals of the New York Academy of Sciences, 2006Co-Authors: Karin Andreassen, Jurgen Mienert, Petter Bryn, Satish C. SinghAbstract:: An unusual pattern of two bottom simulating reflections (BSRs) has been observed on seismic profiles from the continental margin offshore Western Norway. One of these reflections (BSR1) extends over large areas and has the characteristics of the classical BSR, that is a phase-reversed reflection from the base of the gas-hydrate stability zone. The second BSR (BSR0) occurs at approximately 70 ms two-way travel time beneath BSR1 and is here called a double BSR. The distribution of BSR0 is more local than that of BSR1 and it does not show the phase-reversal relative to the sea floor reflection that is characteristic for a BSR at the gas hydrate-free gas boundary. Results from an industrial borehole, from full waveform inversion of multichannel seismic data, from high-frequency ocean bottom hydrophones, and interpretation of seismic profiles, clearly indicate that BSR1 is reflected from the base of the methane hydrate equilibrium field. Results from full waveform inversion indicate that BSR0 corresponds to a 16–20 m zone where the velocity drops from about 1.8 km/s to a minimum of 1.4 km/s and then increases again. The low velocity of 1.4 km/s suggests the presence of free gas. The results support the hypothesis that BSR0 is a reflection from the base of gas hydrates containing hydrocarbons with a heavier molecular weight in addition to methane gas. Interference of reflections from the top and base of the low-velocity zone associated with BSR0 explain why BSR0 is not phase-reversed.
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Evidence for a thick free gas layer beneath the bottom simulating Reflector in the Makran accretionary prism
Marine Geology, 2000Co-Authors: Kalachand Sain, Satish C. Singh, Timothy A. Minshull, Richard HobbsAbstract:Abstract Seismic reflection data from the Makran continental margin indicate the presence of a strong and widespread bottom simulating Reflector (BSR). We apply a nonlinear full waveform inversion technique to multichannel reflection data from this area, to investigate the detailed velocity structure and hence the origin of the BSR. Our result shows an abrupt decrease in the compressional wave velocity from 2.2 to 1.3 km/s at a depth of 500 m below the sea-bed. The low velocity zone is unusually thick (∼200–350 m), and may contain large quantities of free gas, similar to some of the recently drilled Blake Ridge sites of ODP Leg 164. The voluminous free gas may have been generated by the dissociation of gas hydrates as a consequence of the upward movement of the base of gas-hydrate stability field, relative to the sediment column, due to uplift and sedimentation in the accretionary wedge.
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Seismic velocity studies of a gas hydrate Bottom-Simulating Reflector on the northern Cascadia continental margin: Amplitude modeling and full waveform inversion
Journal of Geophysical Research: Solid Earth, 1999Co-Authors: T. Yuan, Roy D. Hyndman, Timothy A. Minshull, George D. Spence, Satish C. SinghAbstract:On the northern Cascadia subduction margin, the multichannel seismic amplitude-versus-offset (AVO) behavior of a Bottom-Simulating Reflector (BSR) suggests a P wave velocity change from high-velocity hydrate-bearing sediment to lower velocity sediment containing a small amount of free gas. The observed nonlinear AVO behavior, constant or slightly decreasing amplitudes at near-to-mid offsets and a large-amplitude increase at far offsets, can be reproduced in the models if an S wave velocity enhancement is assumed as expected from hydrate cementation. The AVO behavior of the hydrate BSR is found not to be as useful as was earlier thought for determining the amount of free gas below the BSR. This is because Poisson's ratio change below the BSR due to gas is likely very small in high-porosity unconsolidated sediments. The uncertainty in the models is large, as there is no reliable S wave velocity information for the sediments containing hydrate or gas. AVO modeling alone is not sufficient to distinguish different velocity models across the BSR. Our interpretation of the BSR amplitude behavior is that a P wave velocity increase above the BSR is the main cause of the BSR reflection amplitude increase at large incidence angles. Caution must be taken in applying AVO analysis, as little is known about S wave velocities. However, subtle differences in BSR amplitude behavior and reflection waveform can provide constraints through very careful full waveform inversion. A well-defined reference velocity-depth profile is also required to represent water-saturated sediment unaffected by either hydrate or free gas. Using full waveform velocity inversion, a high-resolution velocity model for the hydrate BSR has been derived. The best fit model for the seismic data near the Ocean Drilling Program (ODP) sites 889/890 consists of a high-velocity zone above the BSR and a thin low-velocity layer below, in agreement with the ODP downhole velocity data.
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Velocity structure of a bottom simulating Reflector offshore Peru: Results from full waveform inversion
Earth and Planetary Science Letters, 1996Co-Authors: Ingo A Pecher, Satish C. Singh, Timothy A. Minshull, Roland Von HueneAbstract:Much of our knowledge of the worldwide distribution of submarine gas hydrates comes from seismic observations of Bottom Simulating Reflectors (BSRs). Full waveform inversion has proven to be a reliable technique for studying the fine structure of BSRs using the compressional wave velocity. We applied a non-linear full waveform inversion technique to a BSR at a location offshore Peru. We first determined the large-scale features of seismic velocity variations using a statistical inversion technique to maximise coherent energy along travel-time curves. These velocities were used for a starting velocity model for the full waveform inversion, which yielded a detailed velocity/depth model in the vicinity of the BSR. We found that the data are best fit by a model in which the BSR consists of a thin, low-velocity layer. The compressional wave velocity drops from 2.15 km/s down to an average of 1.70 km/s in an 18m thick interval, with a minimum velocity of 1.62 km/s in a 6 m interval. The resulting compressional wave velocity was used to estimate gas content in the sediments. Our results suggest that the low velocity layer is a 6-18 m thick zone containing a few percent of free gas in the pore space. The presence of the BSR coincides with a region of vertical uplift. Therefore, we suggest that gas at this BSR is formed by a dissociation of hydrates at the base of the hydrate stability zone due to uplift and subsequently a decrease in pressure.
Jean-paul Foucher - One of the best experts on this subject based on the ideXlab platform.
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Geophysical characterization of bottom simulating Reflectors in the Fairway Basin (off New Caledonia, Southwest Pacific), based on high resolution seismic profiles and heat flow data
Marine Geology, 2009Co-Authors: Hervé Nouzé, Jean-paul Foucher, Emmanuel Cosquer, Julien Collot, Frauke Klingelhoefer, Yves Lafoy, Louis GéliAbstract:High-resolution reflection and refraction seismic data were collected in 2004 to investigate, in further detail than allowed by pre-existing low resolution seismic data, the nature of a Bottom Simulating Reflector (BSR) that extends over a broad area of the Fairway Basin, a rifted, continental structure located on the eastern flank of the Lord Howe Rise, to the southwest of New Caledonia. Two main Reflectors are documented: the shallower (RN) mimics the seafloor and has a negative polarity while the deeper (RP) does not always mimic the seafloor and has a positive polarity. Using the existing regional seismic lines, we can show that Reflector RN can be continuously followed up to DSDP 208 drill hole site. Reflector RP is discontinuous and cannot be traced to DSDP 208. Based on DSDP 208 stratigraphic data, Reflector RN is assigned to the Eocene/Oligocene regional unconformity; Reflector RP is interpreted in terms of a diagenetic BSR, likely related to an Opal-A/Opal-CT transition front. Heat flow data collected in 2006 suggest that Reflector RP lies too deep to be related to methane hydrates, strengthening our interpretation that RP is of diagenetic origin.
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Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège)
Comptes Rendus Geoscience, 2004Co-Authors: Hervé Nouzé, Isabelle Contrucci, Jean-paul Foucher, Bruno Marsset, Yannick Thomas, Estelle Thereau, Alain Normand, Eliane Le Drezen, Stéphane Didailler, Jean-pierre RegnaultAbstract:The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroit aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating Reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area. Les glissements de Storegga, au large de la Norvege, sont les plus grands glissements connus sur une pente continentale. Lors de la campagne Hydratech sur le N/O Le Suroit, un leve geophysique a haute resolution d'un secteur du flanc nord des glissements a ete effectue. Ce leve permet d'imager en detail l'extension et les proprietes du Bottom Simulating Reflector (BSR), les structures d'echappement de fluides et les deformations sedimentaires. La combinaison des differentes donnees acquises ainsi que leur qualite permettent de mieux comprendre les interactions encore mal contraintes entre fluides, hydrates de gaz et glissements sur la zone d'etude.
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Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège) First results of a geophysical survey on the northern flank of the Storegga slides (Norway).
2004Co-Authors: Hervé Nouzé, Isabelle Contrucci, Jean-paul Foucher, Bruno Marsset, Yannick Thomas, Alain Normand, Eliane Le Drezen, Stéphane Didailler, Jean-pierre RegnaultAbstract:The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroit aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating Reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area.
N. K. Thakur - One of the best experts on this subject based on the ideXlab platform.
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linking methane seepage to fluid flow mechanisms evidence from avo characteristics of bottom simulating Reflectors
Advances in Petroleum Exploration and Development, 2013Co-Authors: Sanjeev Rajput, N. K. Thakur, Prasada P RaoAbstract:The presence of gas hydrates over continental margins may be inferred by various seismic indicators, including the bottom simulating Reflector (BSR). Recently, the occurrence of two BSRs have been reported from many regions of the world. In this study we estimate the uncertainty in amplitude versus offset (AVO) behaviour of the single BSR and double bottom simulating Reflector (DBSR) observed over two geological provinces; the Kerala-Konkan Basin, offshore India and Green Canyon, offshore USA, and attempt to infer a mechanism for the observed anomalies from the AVO patterns. Anomalous behaviour of seismic velocities within the gas hydrate stability zone (GHSZ) associated with the occurrence of DBSRs, low amplitude seismic chimneys and bright spots, indicates increased hydrate concentration and fluid venting structures underneath the DBSR locations. Such structures, if extended upward into the regional GHSZ through discrete fracture networks, may act as a passage for methane escape into the ocean. Our analysis indicates that the variability in AVO signatures for gas hydrate saturated sediments is potentially linked to the discrete zones of steeply inclined fractures that are responsible for the migration of deep gas and its escape through the seabed. Key Words : Methane hydrate; Gas dynamics; Seismic reflections; Plumbing system; Amplitude versus offset (AVO); Bottom simulating Reflector
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Seismic quality factor observations for gas-hydrate-bearing sediments on the western margin of India
Marine Geophysical Researches, 2009Co-Authors: Kalachand Sain, N. K. Thakur, A. K. Singh, Ramesh KhannaAbstract:Any propagating wave undergoes attenuation, which is primarily governed by the physical properties of the medium, determined in terms of quality factor ( Q ). Research into the characteristics of both P- and S-wave Q with reference to gas-hydrates exploration remains in its infancy. Presence of gas-hydrates increases the Q , and this again depends on the nature of distribution and amount of hydrates within the sediments. Thus, estimation of Q provides useful input for both the detection and quantitative assessment of gas-hydrates. Here we propose a simple technique of deriving Q from prestack surface seismic reflection data based on the logarithm of spectral ratio (LSR), and apply the method to marine multi-channel seismic (MCS) data collected on the western margin of India where a bottom simulating Reflector (BSR), which is a prime marker for gas-hydrates, has already been identified. The Q (256 ± 11) estimated over the region with a strong BSR is found to be more than double the Q (101 ± 9) derived for the region without any BSR or a weak BSR. The anomalously high Q with respect to the background can be used to detect gas-hydrates in areas where the BSR is not very clearly observed on seismic sections.
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Full Waveform Seismic Modelling for Gas Hydrate Studies
70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008, 2008Co-Authors: Sanjeev Rajput, N. K. Thakur, A JoshiAbstract:We simulate the seismic response for different models with varying elastic properties to produce a set of plausible seismic signatures for Bottom Simulating Reflectors (BSRs) in different conditions. These simulations are driven by a set of elastic wave equations. We find that the seismic amplitude is very sensitive to the gas hydrates in the host rock. The spatial structure of the reservoir affects the seismic reflection: A thinly-layered reservoir produces noticeably different amplitude strength than a massive reservoir with the same hydrate volume. A model for the occurrence of Double Bottom Simulating Reflector (DBSR) is proposed and validated by real data.
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Fluid flow related features as an indicator of potential gas hydrate zone: western continental margin of India
Marine Geophysical Researches, 2006Co-Authors: Uma Shankar, N. K. Thakur, B. AshalathaAbstract:Multichannel seismic reflection data from the continental margin of western India suggest the potential presence of fluid expulsion features, which may or may not be associated with gas hydrates. No typical bottom simulating Reflector was observed on the reflection seismic section. As a result we look for other evidence in seismic sections in a small corridor of the western continental margin of India in order to establish the presence of gas hydrates. We study features including venting through the seafloor, pockmarks, sea floor collapse, faults acting as migration paths for fluid flow, transparent gas-charged sediment, reduction in amplitude strength, diapirism and mud-volcano. Presence of all these gas-escape features on a seismic section implies the probable presence of methane within the zone of hydrate stability field.
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Two-dimensional elastic anisotropic/AVO modelling for the identification of BSRs in marine sediments using multicomponent receivers
Geo-Marine Letters, 2005Co-Authors: S. Rajput, P. P. Rao, N. K. ThakurAbstract:In seismic sections, the presence of a gas hydrate stability zone (GHSZ) is often marked by a Bottom-Simulating Reflector, which has a negative polarity with respect to the seafloor. The present study reveals the response of seismic wave characteristics and amplitude versus offset (AVO) effects of large offset compressional ( P ) and converted ( PS ) waves for a GHSZ/free-gas configuration, using a two-dimensional elastic anisotropic modelling technique. The modelling results would provide ‘a priori’ information, which allows unique determination of parameters of seismic models for the design of ocean bottom seismometer experiments over continental margins for the purpose of gas hydrate exploration. The AVO analyses on long offset P and PS waves based on synthetic data yield a typical gas hydrate/free-gas response, as the reflectivity increases with incidence angle.