Seismic attributes for characterization of gas hydrate and free gas in the Mahanadi BasinUma Shankar* and Kalachand Sain

CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad-500007umashankar_ngri@yahoo.com

Keywords

Gas hydrates, base of gas hydrate stability zone, seismic attributes, Mahanadi Basin.

Summary

A base of gas hydrate stability zone (BGHSZ) establishedafter gas hydrate drilling and coring in 2006 under NGHPExpedition-01 shows close correspondence with drillingresults in the Mahanadi Basin. The BGHSZ followed byvery high reflectivity on seismic section indicates thepresence of free-gas. Here, we compute the seismicattributes such as the reflection-strength, instantaneousfrequency and phase from seismic data in the MahanadiBasin and demonstrate that these attributes can be used asimportant indicators for the exploration of gas-hydrates andfree-gas. Presence of gas hydrates increases the seismicvelocity and causes amplitude blanking due to hydratecementation. Underlying free-gas saturated sediments havelower velocities than host sediments and exhibit highreflection strength due to variation in gas saturation.Presence of free-gas shows high frequency absorption inthe instantaneous frequency plot. A remarkable lowfrequency and very high reflectivity indicates presence ofgas zones below BGHSZ in the study area.

Introduction

Gas hydrates are ice-like crystalline solid in which gasmolecules (mainly methane) are trapped within cagesformed by water molecules. They are found in the shallowsediments of outer continental margins and permafrostregions at low temperature and high pressure environment(Sloan, 1998; Paul and Dillon, 2001; Milkov, 2004). Gashydratesare indicated mainly by observingbottomsimulating reflector (BSR) on seismic sections, and theirpresence have been validated by drilling and/or coring(Max, 2003; Lu and McMechan, 2004; Kou et al., 2007;Collett et al., 2008). At many places, BSR has not beenfound on seismic section but gas hydrateshave beenrecovered by drilling (Finley and Krason, 1986; Westbrooket al., 1994; Wood and Ruppel, 2000; He et al., 2007).Again, gas hydratesare not found but BSR has beenobserved on seismic section. Hence, we compute somegeophysical attributes to establish whether a BSR is relatedto gas-hydrates and to find out gas hydrates if BSR is notevident.

The presence of gas hydrate in the Mahanadi Basinhas been inferred and established based on seismic studiesand interpretation of well logand core data (Collett et al.,2008; Sain et al., 2012; Shankar and Riedel, 2014). Several

geophysical investigations have been carried out to studythe hydrocarbon prospect and gas hydrate occurrences intothis basin (Bastia et al., 2010). High reflection amplitudeBSRs followed by high reflectivity that may be due to thepresence of free gas have been observed in the central partof the basin (Shankar and Riedel, 2014).In this basin,Tertiary channel–levee complexes are predominantfeatures, which have been documented to be importantcontrolling factors in sediment distribution (in terms oftheir grain size) and thus gas hydrate accumulations (e.g.Riedel et al., 2011). Paleogene and Neogene sections in theMahanadi deep water basin exhibit channel complexes thatare highly flowing (Nath et al., 2006). A flowing channel-levee complex often results in submarine fan lobes towardsthe deeper part of the basin. Incised valley and valley fillsequences are also prevalent during Paleogene andNeogene periods.

The Mahanadi Basin was formed during rifting andbreak-up of Gondwanaland during the Jurassic period. Theareal extent of the basin is about 260,000 km2 includingdeep waters (Mohapatra, 2006). The Mahanadi offshorebasin covers an area of ~80,000 km2 in the Bay of Bengal,south of Bengal shelf, with water depth ranging from ~100m to ~2500 m (Dangwal et al., 2008). The Mahanadi deepwater basin has accommodated more than 8 km of UpperCretaceous to Recent sediments. The bulk of thesesediments were supplied from the Ganga-Brahmaputradeltaic system during the Mio-Pliocene times. During theEarly Paleogene, the basin experienced passive margincarbonate and finer clastic sedimentation, while during theNeogene, it received major fan sediments from the Ganga-Brahmaputra system (Bharali et al., 1991).

The Mahanadi Basin has the favorable temperatureand pressure conditions for the formation of gashydrates.The water depth ranges from 500-2500 m. TheBasin is characterized by geothermal gradients of 35-45oC/km and high sedimentation rate.The overall sedimentflux that is received in this Basin is mainly from theMahanadi river systems (Mahanadi, Brahmani, Baitaraniand Dhamararivers) with a sediment load to the basin onthe order of 7.10 × 109 kg/yr (Subramanian, 1978) and thetotal organic carbon (TOC) content is estimated to be morethan 1.5% (Collett et al., 2008) that favors the formation ofgas hydrates into this region.

Seismic attributes analysis and interpretations arevery useful in identification of methane gas hydrate incomplex geological setup. Seismic attributes (instantaneous

11th Biennial International Conference & Exposition

Seismic attributes for gas hydrate and free gas

amplitude, instantaneous frequency, reflection strength,instantaneous phase and polarity etc.) are derived fromseismic data using complex trace analysis (Mazotti, 1991;Yilmaz, 1987). These seismic attributes were produced bypassing the seismic data through Hilbert transform. In thepresent study, we have computed the reflectionstrength,instantaneous frequency and phase attributes toqualitatively infer the presence of gas hydrate and freegas.Seismic attributes can be extracted along interpretedsurfaces or over volumes, which can be defined betweeninterpreted surfaces or time windows. The extractedattributes are then displayed as attribute maps. It is alsopossible to display the seismic attributes along profiles.

The reflection strength is simply an expression ofthe amplitude envelope of the seismic trace and isindependent of phase (Taner et al. 1979). This attribute isvery useful in identifying the changes in the seismicimpedance contrast and is often associated with thelithologic changes between adjacent rocks such as gashydrate and free gas. Furthermore, lateral variations in bedthickness change the interference of the reflections, therebycausing lateral changes in the reflection strength.

Instantaneous frequency is the derivative of theinstantaneous phase with time. The character of acomposite reflection will change gradually as the sequenceof layers gradually changes in thickness or lithology. Thereflections from the gas bearing zone shift the frequency tothe lower ends. This is because the gas-bearing zonesabsorb high frequency (Taner et al. 1979; Taylor et al.2000). This specific quality of instantaneous frequencyallows discrimination between regions of high and lowattenuation. Low frequency shadows are commonlyassociated with the free gas that occurs below BSRindicating a strong velocity contrast (Taylor et al. 2000;Yilmaz 1987). This means attenuation is higher in free-gas-bearing zones rather than in the hydrate-bearing sediments,because the shorter wavelengths promptly attenuated in theregions of high attenuation.

Method

The seismic data can be interpreted on its own withoutseismic attributes. However, sometime this does notprovide the most detailed subsurface hydrocarbon bearinginformation and can mislead under certain conditions.Seismic attributes are considered important tools for theinterpretation of gas hydrate and free gas in complexgeological system. The seismic attributes are directlyrelated to the subsurface lithology and rock properties andcomputed sample by sample and indicate continuouschange of attributes along the time and spaceaxis.Existence of gas-hydrates and free-gas across a BSRcan thus beestablished by studying the attributes like thereflection strength, instantaneous phase, instantaneousfrequency etc. Pure gas-hydrates have much higher seismic

velocities than those of the pore fluids and shallow hostsediments. Presence of solid gas-hydrates reduces theporosity by filling the pore spaces of sediments (Shipley etal., 1979; Kou et al.,2007) and makes sediments transparentto the passing seismic energy, causing reduction of seismicamplitudesor blanking

Post-stack seismic attributes are derived from thecomplex trace analysis of stacked data. The complex traceanalysis concept described by Taner (1979) and defined as:= [ + ]where, is the complex seismic trace, is the seismictrace and is the Hilbert’s transform of .The reflectionstrength is the signal envelope represents the instantaneousenergy of the signal and is proportional to its magnitude tothe reflection coefficient calculated from the complex traceby formula: = { + }The reflection strength attribute is useful in highlightinggas hydrate and free gas zones, discontinuities,changes inlithology, faults, changes in deposition, tuning effect,sequence boundaries etc.

Instantaneous phase attribute used for the seismicdata interpretation for lateral continuity of the reflectionevents (example, BSR) and sequence boundary continuitiesand can be described as:= | / |The seismic trace and its Hilbert transform are relatedto the envelope and by following relation:= cos ( )= sin ( )It is measured in degree and independent of amplitude.

Instantaneous frequency is the time derivative ofthe phase and described as:= ( )/Instantaneous frequency can indicate bed thickness andlithological parameters.

Examples

Presence of gas-hydrates and free-gas in the sedimentchanges geo-technical properties of the sediment. Thesechanges can be characterized by various seismic attributeslike amplitude blanking, reflection strength andinstantaneous frequency (Ojha and Sain, 2009; Shankar etal., 2014).Presence of gas-hydrates in the pore spaces ofsediments produces amplitude blanking. On the other hand,free-gas in thepore spaces reduces the seismic velocityconsiderably with respect to the host sediment andexhibitsstrongreflectivity. As gas-charged sediments absorbhigh frequency and low frequency domination can beobserved in the instantaneous frequency plot (Taylor et al.,2000). Instantaneous phase plot shows clear continuity ofthe events such as BSR in complex geological setup. Wecalculate these attributes from seismicdata in the Mahanadi

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Seismic attributes for gas hydrate and free gas

Basin where BSR has beenidentified (Collett et al.,2008;Sain et al., 2012; Shankar and Riedel, 2014) andexamined whether the BSR is related to gas-hydrates andfree-gas.

We use seismic data that were made available tothe NGHP through Reliance Industries Ltd., and wereextracted from a larger 3D seismic volume for scientificresearch purpose (Collett et al., 2008). The seismic data setwas also previously used for defining geophysical drillingtargets and site selection for the NGHP Expedition-01.BSR and BSR-like features are identified along availableseismic lines. Figure 1 shows detailed bathymetry map ofMahanadi Basin along with seismic lines passing throughdrilling sites. The BSR depth along seismic lines shownwith color code varies from 200 m to 241 m below seafloor(mbsf). The seismicdata in the study area shows complexstructures and geometries typical of channel (cut-and-fill)deposition (Shankar and Riedel, 2014). The enhancedseismic reflectivity beneath the BSR, mapped usingavailable 3D seismic data, reveals a clear system ofmeandering distributary channels and (to a lesser degree)early fan-type deposits (Fig. 1b). Enhanced reflectionsbelow the BSR are seen in several places and are especiallyprominent where the amplitude of the BSR is high (Fig. 2).In general, enhanced reflections below BSR are laterallyextensive towards SW.

The seismic attributes namely reflection strength(Fig. 3), instantaneous frequency (Fig. 4) and instantaneousphase (Fig. 5) are estimated from the same seismic data inthe Mahanadi Basin. The reflection strength is the envelopeof the seismic signal and represents main seismic featureson seismic section. The envelope represents theinstantaneous energy of seismic signal therefore change ingas hydrate and free gas boundary, faults, unconformitiesetc. interpreted confidently. The high reflectivity and lowinstantaneous frequency attributes characterize the presenceof free-gas below the BSR (Fig. 3 & 4). The instantaneousfrequencies plot exhibits a shift to lower frequency(yellowish pink) beneath the BSR. Presence of a number ofgas-rich/gas-poor strata masks the noticeable frequencyabsorption beneath the BSR (Fig. 4). Instantaneous phaseattribute shows lateral continuity of BSR (Fig. 5), which isindependent of amplitude used for the seismic datainterpretation for lateral continuity of the reflection eventsand sequence boundary continuities.

Figure 1: (a) Study area map with detailed bathymetryshowing the location of the drilling Sites NGHP-01-08, -09,-18 and -19 in the Mahanadi Basin targeted during NGHPExpedition-01. The depth of BSRs superimposed onseismic lines crossing or adjacent to the drilling sites.(b)Time slice of seismic amplitude features showing sedimentfairway system of meandering channel system and earlydevelopment of fan deposits. Data were extracted from a3D seismic volume across the study area in theMahanadiBasin (courtesy M. Mathur, Reliance Industry).Amplitudes were taken from a 20 ms thick window justbeneath the base of gas hydrate stability. Highestamplitudes are shown in yellow (clipped at 50% ofmaximum amplitude value). Seafloor bathymetry issuperimposed on time slice. Drill sites of ExpeditionNGHP-01 (LWD and/or coring with wire-line logging) areshown as red dots (After Shankar and Riedel, 2014).

Seismic attributes for gas hydrate and free gas

Basin where BSR has beenidentified (Collett et al.,2008;Sain et al., 2012; Shankar and Riedel, 2014) andexamined whether the BSR is related to gas-hydrates andfree-gas.

We use seismic data that were made available tothe NGHP through Reliance Industries Ltd., and wereextracted from a larger 3D seismic volume for scientificresearch purpose (Collett et al., 2008). The seismic data setwas also previously used for defining geophysical drillingtargets and site selection for the NGHP Expedition-01.BSR and BSR-like features are identified along availableseismic lines. Figure 1 shows detailed bathymetry map ofMahanadi Basin along with seismic lines passing throughdrilling sites. The BSR depth along seismic lines shownwith color code varies from 200 m to 241 m below seafloor(mbsf). The seismicdata in the study area shows complexstructures and geometries typical of channel (cut-and-fill)deposition (Shankar and Riedel, 2014). The enhancedseismic reflectivity beneath the BSR, mapped usingavailable 3D seismic data, reveals a clear system ofmeandering distributary channels and (to a lesser degree)early fan-type deposits (Fig. 1b). Enhanced reflectionsbelow the BSR are seen in several places and are especiallyprominent where the amplitude of the BSR is high (Fig. 2).In general, enhanced reflections below BSR are laterallyextensive towards SW.

The seismic attributes namely reflection strength(Fig. 3), instantaneous frequency (Fig. 4) and instantaneousphase (Fig. 5) are estimated from the same seismic data inthe Mahanadi Basin. The reflection strength is the envelopeof the seismic signal and represents main seismic featureson seismic section. The envelope represents theinstantaneous energy of seismic signal therefore change ingas hydrate and free gas boundary, faults, unconformitiesetc. interpreted confidently. The high reflectivity and lowinstantaneous frequency attributes characterize the presenceof free-gas below the BSR (Fig. 3 & 4). The instantaneousfrequencies plot exhibits a shift to lower frequency(yellowish pink) beneath the BSR. Presence of a number ofgas-rich/gas-poor strata masks the noticeable frequencyabsorption beneath the BSR (Fig. 4). Instantaneous phaseattribute shows lateral continuity of BSR (Fig. 5), which isindependent of amplitude used for the seismic datainterpretation for lateral continuity of the reflection eventsand sequence boundary continuities.

Figure 1: (a) Study area map with detailed bathymetryshowing the location of the drilling Sites NGHP-01-08, -09,-18 and -19 in the Mahanadi Basin targeted during NGHPExpedition-01. The depth of BSRs superimposed onseismic lines crossing or adjacent to the drilling sites.(b)Time slice of seismic amplitude features showing sedimentfairway system of meandering channel system and earlydevelopment of fan deposits. Data were extracted from a3D seismic volume across the study area in theMahanadiBasin (courtesy M. Mathur, Reliance Industry).Amplitudes were taken from a 20 ms thick window justbeneath the base of gas hydrate stability. Highestamplitudes are shown in yellow (clipped at 50% ofmaximum amplitude value). Seafloor bathymetry issuperimposed on time slice. Drill sites of ExpeditionNGHP-01 (LWD and/or coring with wire-line logging) areshown as red dots (After Shankar and Riedel, 2014).

Seismic attributes for gas hydrate and free gas

Basin where BSR has beenidentified (Collett et al.,2008;Sain et al., 2012; Shankar and Riedel, 2014) andexamined whether the BSR is related to gas-hydrates andfree-gas.

We use seismic data that were made available tothe NGHP through Reliance Industries Ltd., and wereextracted from a larger 3D seismic volume for scientificresearch purpose (Collett et al., 2008). The seismic data setwas also previously used for defining geophysical drillingtargets and site selection for the NGHP Expedition-01.BSR and BSR-like features are identified along availableseismic lines. Figure 1 shows detailed bathymetry map ofMahanadi Basin along with seismic lines passing throughdrilling sites. The BSR depth along seismic lines shownwith color code varies from 200 m to 241 m below seafloor(mbsf). The seismicdata in the study area shows complexstructures and geometries typical of channel (cut-and-fill)deposition (Shankar and Riedel, 2014). The enhancedseismic reflectivity beneath the BSR, mapped usingavailable 3D seismic data, reveals a clear system ofmeandering distributary channels and (to a lesser degree)early fan-type deposits (Fig. 1b). Enhanced reflectionsbelow the BSR are seen in several places and are especiallyprominent where the amplitude of the BSR is high (Fig. 2).In general, enhanced reflections below BSR are laterallyextensive towards SW.

The seismic attributes namely reflection strength(Fig. 3), instantaneous frequency (Fig. 4) and instantaneousphase (Fig. 5) are estimated from the same seismic data inthe Mahanadi Basin. The reflection strength is the envelopeof the seismic signal and represents main seismic featureson seismic section. The envelope represents theinstantaneous energy of seismic signal therefore change ingas hydrate and free gas boundary, faults, unconformitiesetc. interpreted confidently. The high reflectivity and lowinstantaneous frequency attributes characterize the presenceof free-gas below the BSR (Fig. 3 & 4). The instantaneousfrequencies plot exhibits a shift to lower frequency(yellowish pink) beneath the BSR. Presence of a number ofgas-rich/gas-poor strata masks the noticeable frequencyabsorption beneath the BSR (Fig. 4). Instantaneous phaseattribute shows lateral continuity of BSR (Fig. 5), which isindependent of amplitude used for the seismic datainterpretation for lateral continuity of the reflection eventsand sequence boundary continuities.

Figure 1: (a) Study area map with detailed bathymetryshowing the location of the drilling Sites NGHP-01-08, -09,-18 and -19 in the Mahanadi Basin targeted during NGHPExpedition-01. The depth of BSRs superimposed onseismic lines crossing or adjacent to the drilling sites.(b)Time slice of seismic amplitude features showing sedimentfairway system of meandering channel system and earlydevelopment of fan deposits. Data were extracted from a3D seismic volume across the study area in theMahanadiBasin (courtesy M. Mathur, Reliance Industry).Amplitudes were taken from a 20 ms thick window justbeneath the base of gas hydrate stability. Highestamplitudes are shown in yellow (clipped at 50% ofmaximum amplitude value). Seafloor bathymetry issuperimposed on time slice. Drill sites of ExpeditionNGHP-01 (LWD and/or coring with wire-line logging) areshown as red dots (After Shankar and Riedel, 2014).

11th Biennial International Conference & Exposition

Seismic attributes for gas hydrate and free gas

Figure 2: Seismic line crossing site NGHP-01-19. A strongbut patchy BSR is observed along the profile at around 205m below seafloor with complex structure of channel featureand high reflectivity zones below the BSR. Resistivity logis superimposed on the seismic section at the drill sitelocation.

Figure 3: Reflection strength plot along seismic profile.Highest amplitudes strengthis shown in red.

Figure 4: Instantaneous frequency plot along same profile.

Figure 5: The instantaneous phase profile along seismicsection.

Conclusions

In this paper we discusses on some seismic attributes likethe reflection strength, instantaneous frequency and phasethat can be used as important tools for identifying andqualifying gas-hydrates and free-gas across a BSR. Theseattributes can be used at places where BSR is not very clearon seismic section but various other geological,geochemical or microbiological parameters indicate theprobable occurrences of gas hydrates. Strong reflectivityobserved below the BSR is attributed to the gasaccumulations. This is also supported by the absorption ofhigh frequencies in the instantaneous frequency plot.Understanding of all these attributes is essential to drawproper and meaningful conclusions.

References

Bastia, R., Radhakrishna, M., Srinivas, T., Nayak, S.,Nathaniel, D.M., Biswal, T.K., 2010, Structural andtectonic interpretation of geophysical data along theEasternContinental Margin of India with special referenceto the deepwater petroliferous basins; Journal of AsianEarth Sciences, 39, 608-619.

Bharali, B., Rath, S., and Sarma, R.,1991. A brief reviewofMahanadi Delta and the Deltaic sediments inMahanadiBasin; In Quaternary Deltas of India, Memoir 22,GSIpublication.

Collett, T.S., Riedel, M., Cochran, J.R., Boswell, R.,Presley, J., Kumar, P., Sathe, A.V., Sethi, A., Lall, M.,Sibal, V., NGHP Expedition 01 Scientists, 2008, NationalGas Hydrate Program Expedition 01 initial reports;Directorate General of Hydrocarbons, New Delhi.

Dangwal, V., Sengupta, S, and Desai, A.G., 2008,Speculated Petroleum Systems in Deep Offshore Mahanadi

Seismic attributes for gas hydrate and free gas

Figure 2: Seismic line crossing site NGHP-01-19. A strongbut patchy BSR is observed along the profile at around 205m below seafloor with complex structure of channel featureand high reflectivity zones below the BSR. Resistivity logis superimposed on the seismic section at the drill sitelocation.

Figure 3: Reflection strength plot along seismic profile.Highest amplitudes strengthis shown in red.

Figure 4: Instantaneous frequency plot along same profile.

Figure 5: The instantaneous phase profile along seismicsection.

Conclusions

In this paper we discusses on some seismic attributes likethe reflection strength, instantaneous frequency and phasethat can be used as important tools for identifying andqualifying gas-hydrates and free-gas across a BSR. Theseattributes can be used at places where BSR is not very clearon seismic section but various other geological,geochemical or microbiological parameters indicate theprobable occurrences of gas hydrates. Strong reflectivityobserved below the BSR is attributed to the gasaccumulations. This is also supported by the absorption ofhigh frequencies in the instantaneous frequency plot.Understanding of all these attributes is essential to drawproper and meaningful conclusions.

References

Bastia, R., Radhakrishna, M., Srinivas, T., Nayak, S.,Nathaniel, D.M., Biswal, T.K., 2010, Structural andtectonic interpretation of geophysical data along theEasternContinental Margin of India with special referenceto the deepwater petroliferous basins; Journal of AsianEarth Sciences, 39, 608-619.

Bharali, B., Rath, S., and Sarma, R.,1991. A brief reviewofMahanadi Delta and the Deltaic sediments inMahanadiBasin; In Quaternary Deltas of India, Memoir 22,GSIpublication.

Collett, T.S., Riedel, M., Cochran, J.R., Boswell, R.,Presley, J., Kumar, P., Sathe, A.V., Sethi, A., Lall, M.,Sibal, V., NGHP Expedition 01 Scientists, 2008, NationalGas Hydrate Program Expedition 01 initial reports;Directorate General of Hydrocarbons, New Delhi.

Dangwal, V., Sengupta, S, and Desai, A.G., 2008,Speculated Petroleum Systems in Deep Offshore Mahanadi

Seismic attributes for gas hydrate and free gas

Figure 2: Seismic line crossing site NGHP-01-19. A strongbut patchy BSR is observed along the profile at around 205m below seafloor with complex structure of channel featureand high reflectivity zones below the BSR. Resistivity logis superimposed on the seismic section at the drill sitelocation.

Figure 3: Reflection strength plot along seismic profile.Highest amplitudes strengthis shown in red.

Figure 4: Instantaneous frequency plot along same profile.

Figure 5: The instantaneous phase profile along seismicsection.

Conclusions

In this paper we discusses on some seismic attributes likethe reflection strength, instantaneous frequency and phasethat can be used as important tools for identifying andqualifying gas-hydrates and free-gas across a BSR. Theseattributes can be used at places where BSR is not very clearon seismic section but various other geological,geochemical or microbiological parameters indicate theprobable occurrences of gas hydrates. Strong reflectivityobserved below the BSR is attributed to the gasaccumulations. This is also supported by the absorption ofhigh frequencies in the instantaneous frequency plot.Understanding of all these attributes is essential to drawproper and meaningful conclusions.

References

Bastia, R., Radhakrishna, M., Srinivas, T., Nayak, S.,Nathaniel, D.M., Biswal, T.K., 2010, Structural andtectonic interpretation of geophysical data along theEasternContinental Margin of India with special referenceto the deepwater petroliferous basins; Journal of AsianEarth Sciences, 39, 608-619.

Bharali, B., Rath, S., and Sarma, R.,1991. A brief reviewofMahanadi Delta and the Deltaic sediments inMahanadiBasin; In Quaternary Deltas of India, Memoir 22,GSIpublication.

Collett, T.S., Riedel, M., Cochran, J.R., Boswell, R.,Presley, J., Kumar, P., Sathe, A.V., Sethi, A., Lall, M.,Sibal, V., NGHP Expedition 01 Scientists, 2008, NationalGas Hydrate Program Expedition 01 initial reports;Directorate General of Hydrocarbons, New Delhi.

Dangwal, V., Sengupta, S, and Desai, A.G., 2008,Speculated Petroleum Systems in Deep Offshore Mahanadi

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Seismic attributes for gas hydrate and free gas

Basin in Bay ofBengal, India; In proceeding of 7thInternational Conference and Exposition on PetroleumGeophysics, Hyderabad, India.

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Nath, P.K., Samajdar, C., et al., 2006. Depositional systemof deep watersetting for understanding of hydrocarbon playwith reference toMahanadi basin; Oil and National GasCorporation (ONGC) report for internal circulation.

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Seismic attributes for gas hydrate and free gas

Acknowledgements

We thank the Director NGRI for his kind permission topresent this work. We would like to acknowledge DGH,ONGC and the scientists and crew-members of Expedition01 Indian NGHP, who acquired the log and core data.Inaddition, U Shankar is gratefulto the Indo-US Science andTechnology Forum (IUSSTF), Govt. of India, New Delhifor the Indo-US Fellowship-2013.

11th Biennial International Conference & Exposition