india national gas hydrate program expedition 02 operational and technical summary abstract the india national gas hydrate program is being steered by the government of india s ministry of petroleum and natural gas mopng with participation of directorate general of hydrocarbons dgh oil and natural gas corporation limited ongc and the national oil companies and research institutes of india the india national gas hydrate program expedition 01 nghp 01 established the presence of gas hydrate in the krishna godavari kg and mahanadi basins and in the offshore area of the andaman sea basin however the gas hydrates discovered during nghp 01 were mainly distributed as fracture filling material in fine grained clay rich sediments the india national gas hydrate program expedition 02 nghp 02 was carried out with an objective to discover gas hydrate in sand rich sediment along the eastern offshore margin of india ongc planned and executed nghp 02 on the behalf of the mopng nghp 02 started on march 3 2015 and was completed on july 28 2015 total 147 days using the japanese scientific drilling vessel chikyu d v chikyu during nghp 02 42 holes at 25 sites were drilled cored and or surveyed with downhole logging tools these sites were located in four areas along the eastern margin of india and formally named area a mahanadi basin three sites area b northern part of the kg basin twelve sites area c central part of the kg basin six sites and area e southern part to the kg basin four sites all 25 sites established during nghp 02 were first drilled and logged with logging while drilling lwd tools and an additional 17 holes were then drilled and or cored with conventional coring tools hpcs escs or pressure coring tools pctb wireline logging was conducted in 10 holes and formation tests using a dual packer modular formation dynamics tester mdt tool were carried out in two holes the onboard science team used the laboratory facilities on the d v chikyu to examine and analyse the physical properties geochemistry and sedimentology of all the cores collected during the expedition core samples were also analysed in additional post expedition shore based studies conducted in numerous domestic and international gas hydrate research laboratories the nghp 02 sediment cores were archived at the national gas hydrate core repository in mumbai india which is associated with the ongc gas hydrate research and technology centre ghrtc the necessary data for characterizing the occurrence of gas hydrate such as interstitial water chlorinities core derived gas chemistry physical and sedimentological properties thermal images of the recovered cores pressure core and downhole measured logging data lwd and or conventional wireline log data were obtained from most of the drill sites established during nghp 02 almost all the drill sites yielded evidence for the occurrence of gas hydrate however the inferred in situ concentration of gas hydrate varied substantially from site to site for the most part the interpretation of downhole logging data core thermal images interstitial water analyses and pressure core images from the sites established during nghp 02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained sand rich sediments this paper presents the operational and technical summary of nghp 02

water and gas chemistry at lake kivu drc geochemical evidence of vertical and horizontal heterogeneities in a multibasin structure 1 waters and dissolved gases collected along vertical profiles in the five basins main kabuno bay kalehe ishungu and bukavu forming the 485 m deep lake kivu democratic republic of the congo were analyzed to provide a geochemical conceptual model of the several processes controlling lake chemistry the measured horizontal and vertical variations of water and gas compositions suggest that each basin has distinct chemical features produced by 1 different contribution from long circulating fluid system containing magmatic co2 responsible of the huge co2 ch4 rich reservoir hosted within the deep lake water 2 spatial variations of the biomass distribution and or speciation and 3 solutes from water rock interactions the kabuno bay basin is characterized by the highest rate of magmatic fluid input accordingly this basin must be considered the most hazardous site for possible gas outburst that could be triggered by the activity of the nyiragongo and nyamulagira volcanoes located a few kilometers north of the lake

holocene aridification of india 1 spanning a latitudinal range typical for deserts the indian peninsula is fertile instead and sustains over a billion people through monsoonal rains despite the strong link between climate and society our knowledge of the long term monsoon variability is incomplete over the indian subcontinent here we reconstruct the holocene paleoclimate in the core monsoon zone cmz of the indian peninsula using a sediment core recovered offshore from the mouth of godavari river carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the cmz and document a gradual increase in aridity adapted vegetation from 4 000 until 1 700 years ago followed by the persistence of aridity adapted plants after that the oxygen isotopic composition of planktonic foraminiferglobigerinoides ruberdetects unprecedented high salinity events in the bay of bengal over the last 3 000 years and especially after 1 700 years ago which suggest that the cmz aridification intensified in the late holocene through a series of sub millennial dry episodes cultural changes occurred across the indian subcontinent as the climate became more arid after 4 000 years sedentary agriculture took hold in the drying central and south india while the urban harappan civilization collapsed in the already arid indus basin the establishment of a more variable hydroclimate over the last ca 1 700 years may have led to the rapid proliferation of water conservation technology in south india

rise of the base of the gas hydrate zone since the last glacial recorded by rock magnetism gas hydrate a clathrate of methane and water widespread on continental margins has been implicated as a trigger of climate change and submarine slides as a result of methane release when the base of its stability zone moves upward rapidly direct tests of these hypotheses are made difficult by the ephemeral record of gas hydrate in sediment in places a seismic reflector double bottom simulating reflector bsr appears to mark the old base of the gas hydrate layer but the occurrence of this feature is patchy and its interpretation is controversial microbial activity is stimulated in the presence of gas hydrate and results in the production of magnetic iron sulfides the base of the gas hydrate interval is marked by a sharp reduction in the magnetic hysteresis parameter d j h at hydrate ridge on the cascadia margin sampled during ocean drilling program leg 204 this signature occurs between 20 and 65 m below the present day base of the gas hydrate zone at a depth consistent with predictions for the base of gas hydrate stability given water depths and bottom water temperatures appropriate for the last glacial maximum seismic evidence for a double bsr over part of hydrate ridge corroborates the rock magnetic interpretation

origin of gas in gas hydrates as interpreted from geochemistry data obtained during the national gas hydrate program expedition 02 krishna godavari basin offshore india abstract this report presents the result of geochemical studies carried out on cores recovered from krishna godavari basin k g basin during the national gas hydrate program expedition 02 nghp 02 nghp 02 targeted gas hydrate accumulations in sand facies in the k g basin off the east coast of the indian peninsula three areas area b area c and area e in the k g basin were investigated during this expedition 10 research sites in k g basin were cored and samples for geochemistry analysis were collected high toc tn ratios indicate an input from terrestrial organic matter analysis of gas samples from pressure cores also acquired during nghp 02 were composed of mostly methane carbon isotopic studies show that methane gas sampled from recovered gas hydrate samples were derived from biogenic microbial sources this list of factors appears to indicate that the gas associated with the recovered hydrate bearing core samples were derived from a microbial source however the biogeochemical processes responsible for generating the microbial gases found with the recovered gas hydrates may not have been limited to current limits off the gas hydrate stability zone it is important to note here that microbial process likely extend to more than 1 km deep into the basin so gas coming from below the gh stability zone can still be from a microbial source in addition the microbial gas within the stability zone was likely in part recycled from hydrate accumulations that has passed through the base of the gas hydrate stability zone as a product of sedimentation with the dissociated microbial gas migration again vertically in the section entering the gas hydrate stability zone and reforming gas hydrates although the organic carbon required for in situ methanogenesis and gas hydrate formation is abundant in the shallow sedimentary section of the kg basin the faulted fractured and deformed stratigraphy observed in the kg basin coupled with high pore filling gas hydrate saturations at many sites suggests that advective processes may be contributing to the supply of methane to the gas hydrates in the kg basin the possible migration of gas from greater depths is also supported by seismic evidence of through going migration pathways that can connect the gas hydrate system with deeper petroleum systems it is important to note here that the deep conventional gas accumulations in the basin also contain microbially sourced gas

the evolution of the east coast of india abstract the evolution of the east coast of india from the permian up to the end of the cretaceous is traced peninsular india had an imprint of hercynian epeirogeny manifested in the formation of some regional geofracture and rift systems the east coast basins mahanadi godavari krishna palar and cauvery basins are pericratonic the structural style and regional trends during the jurassic are ne sw the basin architecture during the late jurassic is of horst graben type the close of the mesozoic was marked by regional easterly regression basinal tilt and formation of monoclinal post mesozoic sedimentary cover the oldest sequence in these basins is of permian age and is known in the palar basin the triassic sediments are not known in the land area from the faunistic and floristic evidence the uppermost jurassic lower cretaceous gondwana sediments are paralic the occurrence of marine permian palynofossils in the indian east coast sediments points to the presence of a narrow paleo shelf to the east prior to the break up and drift of gondwanaland different continental fits offered by various authors are analysed to understand the evolution of the indian ocean the structural grain and basin architecture of the pre drift and post drift basins of the east coast of india are similar to that of the western and northwestern coastal basins of australia it is postulated that permian sediments were extensive and have since been eroded such a pattern of erosion of permian beds is also observed in northwestern australia the most favoured fit of western australia against northern india does not conform to the regional geotectonic pattern and the nature of sediments that are present in india and the australian counterparts in addition to geological evidence palaeo biological evidence has been considered which favours the juxtaposition of the east coast of india with western australia the authors are of the opinion that palaeomagnetic interpretations which have of late gained importance fail to explain the pre drift geological similarities of the east coast of india and western coast of australia

an overview of indian sedimentary basins with special focus on emerging east coast deepwater frontiers this article will provide an overview of the current indian petroleum exploration scenario with special focus on the east coast deepwater basins an attempt has been made to distinguish the hydrocarbon system and play types for both rift related and other structural styles using high quality 2d and 3d seismic imaging information integrating the geologic information with state of the art seismic data has generated a large portfolio of play types e g channel levee complex lobes synrift structural closures and wedge outs against basement highs worthy of exploration

environmental changes and human impact as recorded in a sediment sequence offshore from a viking age town birka southeastern sweden the viking age town of birka which existed between ad 750 and 975 on the island of bjorko in the malar archipelago of the baltic sea is known as the oldest centre used for large scale international trading in sweden birka had a strong defence town rampart hillfort and a water palisade studies of lithology and microand macroremains in a sedimentary sequence accumulated offshore from birka outside the water palisade revealed a stratigraphically distinct refuse stratum referred to as the birka layer we argue that the bulk material of the birka layer emanates from human activities in the town e g latrine cleanings cuttings of shore vegetation cleaning of ditches and storage areas and domestic animal dung organic remains from vegetation and animals deposited during activities on the ice offshore from the town e g winter markets may also have contributed to the composition the material constituting the birka layer started to accumulate after the construction of the protecting water pali

multi measurement approach for establishing the base of gas hydrate occurrence in the krishna godavari basin for sites cored during expedition nghp 02 in the offshore of india abstract the 2015 national gas hydrate program of india s second expedition nghp 02 acquired logging and coring datasets for constraining the base of the gas hydrate occurrence zone deepest gh and the theoretical base of gas hydrate stability zone bghs these data are used here for two primary goals to constrain the deepest occurrence of gas hydrate relative to predicted stability limits and the observed bsr and to characterize the nature of the contact between gas hydrate bearing sediment and the underlying gas hydrate free sediment a consensus depth for the deepest gh is derived for each nghp 02 coring site from downhole indicators of gas hydrate occurrence obtained from well log electrical resistivity and acoustic data pressure core compressional wave velocity measurements and conventional core measurements of anomalously low temperatures to establish the theoretical bghs models of gas hydrate phase stability with depth are compared with downhole temperature profiles derived from 1 assuming a constant geothermal gradient consistent with downhole temperature measurements and 2 assuming constant heat flow using a geotherm through the downhole temperature measurements and incorporating thermal conductivity calculated from borehole logging data although the deepest nghp 02 gh occurrences are controlled at several sites by a lithologic boundary most sites have deepest gh occurrences within a single coarse grained lithology cutoffs within a single coarse grained lithology which occur for the primary nghp 02 area b gas hydrate reservoir will inhibit pore pressure drawdowns used to extract methane from gas hydrate as an energy resource

an 8000 year record of sea level change from grain size parameters data from beach ridges in denmark the low energy beach ridge system near the town of jerup in the extreme north of denmark was sampled at 154 sites on a pattern of one per ridge intervals of 50 51 years starting about 7800 bp

quaternary evolution of the ria de vigo spain abstract the seismic analysis of the sedimentary infill of the ria de vigo reveals that the infill comprises of a fifth order sequence 18 ky bounded by a major discontinuity surface within the holocene sequence several seismic units have been identified the oldest one originated after the wurm glaciation and the origin of its top discontinuity was eroded during the regression sea level at 120 m of this last glacial episode isotopic stages 2 to 4 18 ky b p in some places below this ria infill another sequence can be identified this older sequence is associated with the pre existing faults and troughs in the deepest parts of the ria and it was deposited during the wurm glaciation miocene pleistocene eroded sediments were moved from the rias area to deeper zones where they accumulated in the lowstand system tract the next sea level rise occured in two steps producing two transgressive units separated by an hiatus surface this cycle was interrupted by the next sea level fall to 55 m marked on the seismic records by another recognizable boundary the next sea level rise took place in several steps back stepping with some stillstands generating another transgressive system tract in the ria from that time on the relative sea level continued rising depositing the most recent unit which represents the highstand system tract separating the highstand system tract and the transgresive unit below there is a consensed section the analysis of 29 cores provides groundtruthing for our hypothesis the identified main lithologic units show a transgressive sequence a granitic rock base an overlying second unit locally wedge shaped and most recently a marine muddy unit covering the present ria seafloor

sediment transport of the godavari river basin and its controlling factors abstract the mean annual water flow and sediment transport of the godavari river are estimated to be 92 km 3 and 170 10 6 ton t respectively in terms of sediment transport and the rate of physical erosion 555 t km 2 yr 1 the position of the godavari would be ninth and fifth respectively among the world rivers geology of the basin is the main controlling factor of the sediment transport the sedimentary rocks located in the lower part of the basin and constituting 7 of the total basin area are responsible for 33 of the sediment load more than 67 of sediment load is silt and clay annual monthly and daily variations in sediment transport indicate that a few selected days in the hydrological year control the annual sediment budget our latest estimates are nearly twice that of our earlier values the presently available global estimates on sediment transport need to be re evaluated

national gas hydrate program expedition 01 offshore india gas hydrate systems as revealed by hydrocarbon gas geochemistry abstract the national gas hydrate program expedition 01 nghp 01 targeted gas hydrate accumulations offshore of the indian peninsula and along the andaman convergent margin the primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems four areas were investigated 1 the kerala konkan basin in the eastern arabian sea 2 the mahanadi and 3 krishna godavari basins in the western bay of bengal and 4 the andaman forearc basin in the andaman sea upward flux of methane at three of the four of the sites cored during nghp 01 is apparent from the presence of seafloor mounds seismic evidence for upward gas migration shallow sub seafloor geochemical evidence of methane oxidation and near seafloor gas composition that resembles gas from depth the kerala konkan basin well contained only co2 with no detectable hydrocarbons suggesting there is no gas hydrate system here gas and gas hydrate from the krishna godavari basin is mainly microbial methane with 13c values ranging from 58 9 to 78 9 with small contributions from microbial ethane 52 1 and co2 gas from the mahanadi basin was mainly methane with lower concentrations of c2 c5 hydrocarbons c1 c2 ratios typically 1000 and co2 carbon isotopic compositions that ranged from 70 7 to 86 6 for methane and 62 9 to 63 7 for ethane are consistent with a microbial gas source however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source gas composition in the andaman basin was mainly methane with lower concentrations of ethane to isopentane and co2 c1 c2 ratios were mainly 1000 although deeper samples were

pre breakup continental extension in east gondwanaland and the early opening of the eastern indian ocean abstract extension of continental crust by up to 360 km on a north northeast azimuth in the great australian bight occurred prior to the middle cretaceous 96 ma onset of seafloor spreading between australia and antarctica this large amount of continental extension is constrained to the late jurassic 160 ma middle cretaceous interval about a pole estimated to lie about 40 southeastward of southeastern australia using bathymetric data combined with seismic and magnetic determinations of the continent ocean boundaries off australia india and antarctica we determine a revised fit of east gondwanaland prior to continental extension and at various stages thereafter in the first stage from 160 to 132 5 ma m11 india australia rotated from antarctica with continental crustal extension between australia and antarctica and largely transform motion between the coromandel coast margin of india and the kron prins olav kyst margin of antarctica in the second stage from 132 5 to 96 ma india rotated northwestward away from australia antarctica producing m10 and younger magnetic anomalies along the western margin of australia continental extension was greatest between australia and antarctica during this stage the newly determined 132 5 96 ma rotation between india and australia provides an improved fit between the orientation of observed m10 m0 magnetic anomalies and the southward decrease in spreading rate off the western australian margin together with bathymetry the new rotation parameters lead to identification of the abandoned 96 ma spreading ridge along the lost dutchmen and dirck hartog ridges the naturaliste fracture zone is found to lie nearly parallel to the early cretaceous transform direction between india and antarctica suggesting that slow seafloor spreading required between australia and antarctica to accommodate the continental extension further east occurred between naturaliste fracture zone and the m4 m0 anomalies adjacent to the naturaliste plateau the revised fit of india in east gondwanaland reduces the eastward extent of greater india to 95 e but does not change its extent as far north as the cape range fracture zone the new pole determined for the early cretaceous rotation between india and australia antarctica lies within 15 of the southern tip of india significantly closer than in previous determinations thereby reducing the amount of seafloor spreading generated between africa and antarctica by the india antarctica rotation and thus offering a possible solution to the perceived spreading rate problems between m11 and m0 in the somali mozambique and antarctic basins

multi proxy evidence of late holocene human induced environmental changes at lake pupuke auckland new zealand abstract new zealand was the last major landmass in the world to be colonised by people despite the short time depth of human presence in the country there is ongoing debate about the date of earliest arrival of people that resulted in the emergence of two contrasting colonisation hypotheses the early hypothesis and the short prehistory to decide between both hypotheses we employed a range of multi proxy investigations geochemistry stable isotopes and mineral magnetism on a lacustrine sequence from lake pupuke a maar lake in the city of auckland and an area potentially among the first places in new zealand to have been colonised by early people the environmental history reconstructed from the multi proxy evidence identified a clear lack of catchment disturbance from c 2000 b p until several decades before the eruption of the rangitoto volcano the nature and abruptness of disturbance unambiguously point to anthropogenic forcings and are likely to mark the onset of prehistoric human colonisation at the site linear interpolation between independently dated tephrochronostratigraphic marker beds present in the sediments allowed to date this event to c 610 cal yr b p this date is in compliance with the short prehistory for this region

deglaciation holocene shore displacement and coastal settlements in eastern svealand sweden abstract detailed mapping of the clay varve sediments and stratigraphical analysis of isolated lake basins on the sodertorn peninsula have been undertaken as part of the research project eastern svealand development of the holocene landscape the varve studies have identified three distinctive stratigraphical units and indicate that deglaciation took place between 11 400 and 10 400 clay varve years bp initially recession of the ice margin was slow but subsequently it became more rapid study of 15 isolation basins has allowed a tentative shore displacement curve to be constructed for the area this curve is marked by varied rates of regression and possibly displays 3 litorina transgressions the curve suggests markedly different ages for the transgression events than those proposed by earlier authors and this is assessed in terms of curve construction and dating errors archaeological evidence indicates that coastal settlements changed their altitudinal location in response to changes in sea level this evidence supporting the data derived from isolation basins

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

origin of low chloride fluid in sediments from the eastern continental margin of india results from the national gas hydrate program expedition 02 abstract national gas hydrate program expedition 02 was conducted in 2015 by d v chikyu in the western bay of bengal india analyses of interstitial water in sediment from four drilling sites along the eastern and western transect in the krishna godavari basin show that dissolved chloride cl concentrations decreased with depth from seawater values 550 mm near the sediment surface to 300 400 mm at 350 400 m below seafloor mbsf suggesting the upward advection of low cl fluid excursions of cl concentrations toward low values in gas hydrate zones were attributed to the presence of fresh water released by dissociation of gas hydrate during core recovery at sites in the western transect cl concentrations below the gas hydrate reservoir around 280 mbsf were ca 60 mm and ca 45 mm lower than those from above the reservoir and 18o and d values were 1 2 and 0 7 1 3 higher than those from above the reservoir respectively these results suggest that a fraction of migrating low cl fluid is trapped in the gas hydrate zone causing decreases of 18o and d in the residual water due to isotopic fractionation during gas hydrate formation from mass balance calculations we estimated that 10 20 of the advected fluid is trapped at the gas hydrate zone at all sites the 18o and d values below the gas hydrate zone representing relatively unaltered low cl fluid were 0 5 1 higher and ca 13 15 lower than those of seawater respectively this trend is consistent with water derived from the dehydration of clay minerals which generally occurs in deeply buried sediments the contribution of clay mineral dehydration is relatively large at the western transect compared to that in the eastern transect our results imply that fluid advection contributes to the accumulation of gas hydrate in the study area

sedimentation stratigraphy and petroleum potential of krishna godavari basin east coast of india the krishna godavari basin is located in the central part of the eastern passive continental margin of india the structural grain of the basin is northeast southwest exposures of upper cretaceous sedimentary rocks demarcate the basin margin toward the north west where the northwest southeast trending pranahita godavari graben abuts the basin the basin contains thick sequences of sediments with several cycles of deposition ranging in age from late carboniferous to holocene a major delta with a thick argillaceous facies that has prograded seaward since the late cretaceous is a hydrocarbon exploration target magnetic and gravity data predicted the basin architecture which was subsequently confirmed by a multichannel seismic sur vey the basin is divided into subbasins by fault controlled ridges sediments accumulated in subbasins more than 5 km thick above the basement ridges thin sediments are found until the jurassic period sediments were deposited in the rift valley and in topo graphic lows this sequence is completely overlain by a lower cretaceous transgressive sedimentary wedge later continued delta progradation characterized basin sedimentation with an areal extent of approximately 45 000 km2 this proven petroliferous basin has potential reservoirs ranging in age from the permian to the pliocene exploratory drilling of more than 350 wells in more than 160 structures has resulted in the discovery of 42 oil and gas bearing structures good source rocks are known from sequences ranging in age from permian carboniferous to early miocene because the reservoir sand bodies have limited lateral variation understanding the stratigraphy and depositional sub environments in different sequences is essential to decipher the favorable locales for reservoir sands tilted fault blocks growth faults and related rollover anticlines provide the structural traps begin page 1624

gas hydrate reservoir identification delineation and characterization in the krishna godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition offshore india abstract during the national gas hydrate program expedition 02 nghp 02 logging while drilling conventional coring and pressure coring wire line logging vertical seismic profiling and formation pressure measurements were carried out in deep water portions of the krishna godavari k g and mahanadi basins along the eastern continental margin of india a total of 42 research holes were completed for comprehensive data collection and measurements related to gas hydrate reservoir and host sediments properties with an objective to identify producible gas hydrate in sand rich reservoirs that would be suitable for a future pilot production test shipboard and post cruise evaluation of physical properties measurements pressure core dissociation studies and gas analysis of recovered core samples have confirmed the occurrence of sand hosted gas hydrate deposits in three operational areas named during nghp 02 as area b area c and area e in the deep water portion of the k g basin the energy resource potential of the discovered gas hydrate deposits in the k g basin depends on many factors including the quantity of available gas trapped as gas hydrate in the basin therefore this study was undertaken to identify characterize and delineate the discovered and confirmed gas hydrate prospects in the k g basin based on the integrated analysis of regional seismic data and nghp 02 acquired borehole data a total of 8 sand rich reservoir constrained gas hydrate prospects have been identified and mapped in the k g basin areas b c and e as described in this report

seabed morphology and gas venting features in the continental slope region of krishna godavari basin bay of bengal implications in gas hydrate exploration abstract increased oil and gas exploration activity has led to a detailed investigation of the continental shelf and adjacent slope regions of mahanadi krishna godavari kg and cauvery basins which are promising petroliferous basins along the eastern continental margin of india in this paper we analyze the high resolution sparker subbottom profiler and multibeam data in kg offshore basin to understand the shallow structures and shallow deposits for gas hydrate exploration we identified and mapped prominent positive topographic features in the bathymetry data these mounds show fluid gas migration features such as acoustic voids acoustic chimneys and acoustic turbid layers it is interesting to note that drilling coring onboard joides in the vicinity of the mounds show the presence of thick accumulation of subsurface gas hydrate further geological and geochemical study of long sediment cores collected onboard marion dufresne in the vicinity of the mounds and sedimentary ridges shows the imprints of paleo expulsion of methane and sulfidic fluid from the seafloor to understand the origin of the mounds and their relationship with gas hydrate cold seep formation we analyzed the multi channel seismic reflection mcs data close to the mounds the mcs data show that the subsurface layers beneath the mounds are folded below the folded overburden we observe zones of no coherent reflections probably originating from miocene sequence since the study area is located in shale tectonics regime where miocene sequences are known to be overpressured we interpret the zones of no coherent reflections as miocene shale diapirs the upward movement of shale diapirs has folded the overburden layer and resulted in the formation of numerous faults fractures these faults act as permeable pathways for fluid gas movement facilitating the formation of gas hydrate and cold seeps close to shale diapiric mound

geochemical and geological constraints on the composition of marine sediment pore fluid possible link to gas hydrate deposits abstract pore water sulfate consumption in marine sediments is controlled by microbially driven sulfate reduction via organo clastic and methane oxidation processes in this work we present sediment pore fluid compositions of 10 long sediment cores and high resolution seismic data from the krishna godavari k g basin bay of bengal our results show occurrence of transient s and kink types and steady state quasi linear sulfate concentration profiles which are attributed partly to the anaerobic oxidation of methane 13 c ch 4 84 8 to 100 1 vpdb and organo clastic sulfate reduction influence of aom on alkalinity is evident from the presence of authigenic carbonate layers with highly depleted carbon isotope ratios in core md161 8 the authigenic carbonates represent the paleo smtzs and suggest marked fluctuation in vertical methane flux our geophysical data show the acoustic signatures of upward fluid migration from shallow sub surface whereas coring during nghp expedition 01 confirms the presence of sub surface gas hydrate deposits in k g basin which can be linked to deep methane sources the geochemical analysis suggests that shallow methane source can be attributed to high burial flux of labile organic matter due to high sedimentation rate sampling sites with high methane flux from the shallow gas source are characterized by quasi linear sulfate concentration profile and a shallow sulfate methane transition zone smtz and may not be necessarily linked to deeper gas hydrate deposits in contrast the deep methane source results in a transient kink type sulfate profile and a deeper smtz we have observed a close link between the occurrence of gas hydrate and the s kink type sulfate profile we interpret the short lived kink in the sulfate profiles as a result of recent enhancement in vertical methane flux possibly driven by reactivation of fault fractures systems which provide the conduits for fluid flow

evidence of paleo cold seep activity from the bay of bengal offshore india 1 we report evidence of paleo cold seep associated activities preserved in methane derived carbonates in association with chemosynthetic clams calyptogena sp from a sediment core in the krishna godavari basin bay of bengal visual observations and calculations based on high resolution wet bulk density profile of a core collected on board r v marion dufresne may 2007 show zones of sharp increase in carbonate content 10 55 vol within 16 20 meters below seafloor mbsf the presence of calyptogena clam shells chimneys shell breccias with high mg calcite cement and pyrite within this zone suggest seepage of methane and sulfide bearing fluid to the seafloor in the past highly depleted carbon isotopic values 13c ranges from 41 to 52 vpdb from these carbonates indicate carbon derived via anaerobic oxidation of methane extrapolated mean calendar age 58 7 ka b p of the clastic sediments at a depth of 16 mbsf is close to the upper limit of the u th based depositional age 46 2 3 7 and 53 0 1 6 ka of authigenic carbonates sampled from this level thereby constraining the younger age limit of the carbonate deposition methane expulsion events the observed carbonate deposition might have resulted from the flow of methane enriched fluids through the fracture network formed because of shale diapirism

the importance of brownfields gold exploration significant growth in the size of gold resources on many mines of the yilgarn craton has occurred well after the deposit was discovered and after mining had commenced examples include the kalgoorlie and norseman goldfields found more than a century ago and the jundee and sunrise goldfields discovered in the 1990s the initial discovery event is referred to as greenfields exploration and the later additions as brownfields exploration for the yilgarn craton annual resource additions have significantly exceeded mine depletion since 1980 brownfields exploration enjoys economic benefits not available to greenfields exploration such as reduced infrastructure and regulatory costs in australia criticism of the exploration and mining industry for failing to find deposits is misplaced

basin architecture and petroleum system of krishna godavari basin east coast of india krishna godavari basin is a peri cratonic passive margin basin on the east coast of india figure 1 the onland part consists of 28 000 km2 and is mostly alluvium covered krishna and godavari are the two major river systems which drain the area and discharge in the bay of bengal the offshore basinal area covers 24 000 km2 to the isobath of 200 m however the basin extends into deeper water and covers a much larger area the basin s characteristic feature is its en echelon horst and graben system which is filled with a thick pile of sediments of permian to recent age and emerging as one of india s most promising petroliferous areas commercial accumulation of hydrocarbons occurs in sediments from the permian to as young as the pliocene

sedimentation rates from calcareous nannofossil and planktonic foraminifera biostratigraphy in the andaman sea northern bay of bengal and eastern arabian sea abstract in this study we determined calcareous nannofossil and planktonic foraminifera events in sediments recovered during the 2006 indian national gas hydrate program nghp expedition 01 selected bioevents permitted the assignment of orbitally calibrated ages derivative sedimentation rate estimates and identification of sedimentary discontinuities in the andaman sea at hole nghp 01 17a a late miocene to recent record was recovered but with a significant hiatus during the latest miocene and pliocene sedimentation rates here vary from 50 m myr during the pleistocene to 130 m myr for the late miocene in the northern bay of bengal at hole nghp 01 19a the base of the cored record also reaches the late miocene and extends to recent but the same hiatus missing the pliocene is present at this hole a the early pleistocene at hole nghp 1 19a shows sensible variation in sedimentation rates ranging between 130 m myr and 10 m myr during the last 0 5 ma for the late miocene the sedimentation rate was ca 50 m myr in the western bay of bengal at hole nghp 01 10b d calcareous nannofossils were sparse and only foraminifera datums are available the base of the section is latest early pliocene to late pliocene and the majority of the record is considered younger than late pliocene due to the scarcity of calcareous nannofossils and the few foraminifera datums sedimentation rates were not determined here however hole nghp 01 16a in the same region recorded the highest occurrence of pseudoemiliania lacunosa an event that confirms a pleistocene age allowing us to estimate a sedimentation rate between 110 m myr and 450 m myr along the western peninsular indian margin at hole nghp 01 01a a continuous record from the holocene to the early oligocene indicates sedimentation rates of ca 25 m myr until the middle miocene and a sensible reduction downward reaching 4 m myr in the early miocene to the early oligocene no hiatuses were observed the large changes in sedimentation rates observed in these cores reflect long timescale changes in the environment likely induced by changes in the strength of the indian monsoon system

composition and origin of authigenic carbonates in the krishna godavari and mahanadi basins eastern continental margin of india abstract the mineralogical and stable isotopic composition of authigenic carbonates from the krishna godavari kg and mahanadi basin provide a deeper insight into the processes inducing carbonate formation in the sediments of the eastern continental margin of india in the bay of bengal authigenic carbonate cements micro nodules bioturbation casts and tubes from 12 core locations drilled during the indian national gas hydrate program nghp expedition 01 were investigated for this study three main processes responsible for authigenic carbonate precipitation are identified organoclastic sulfate reduction anaerobic oxidation of methane and methanogenesis evidence of vigorous methane seepage is indicated in carbonates recovered at sites 7 10 12 kg basin and 19 mahanadi basin these methane derived carbonates display typical paragenetic carbonate mineralogies aragonite high mg calcite with 15 mol mgco 3 ca rich dolomite two separate horizons of methane derived carbonates are correlated between 4 drill holes up to 16 km apart the upper horizon has been dated with 14 c 40 100 51 600 a bp 1950 and clearly indicates that methane seepage has been much more vigorous in the past possibly due to the effect of lower sea level on the gas hydrate stability zone across the margin

physical property characteristics of gas hydrate bearing reservoir and associated seal sediments collected during nghp 02 in the krishna godavari basin in the offshore of india abstract india s national gas hydrate program expedition 02 nghp 02 was conducted to better understand geologic controls on gas hydrate occurrence and morphology targeting coarse grained sediments along the lower continental slope offshore eastern india this study combines seismic logging while drilling data and a petroleum system approach to provide a regional geologic and lithologic context for 1 gas hydrate morphology and distribution and 2 effects of fine grained sediments clays and other grains smaller than 63 m on gas production in nghp 02 area b in the krishna godavari basin area b seismic data show a buried anticline syncline structure with strong reflectors r1 and r2 that delineate two of the five lithologic units unit i shallowest ii r1 iii iv r2 and v below the bas of gas hydrate stability throughout area b gas hydrate morphology depends on its placement within these units specifically core and grain scale measurements indicate fines content exerts a primary control on the gas hydrate distribution and morphology units i ii and iii are generally fine grained on the anticline crest these units host primarily grain displacing gas hydrate veins linked to pore occupying gas hydrate in thin localized coarser grained deposits diatoms in unit iii increase porosity with depth reaching 70 where it contacts unit iv the gas hydrate reservoir associated with reflector r2 the unit iii lithology and porosity allow fluid and dissolved phase methane to escape unit iv and form gas hydrate in the fine grained overburden within unit iv fine grained layers are interbedded with coarser grained gas hydrate reservoir sands and the fines content even in the sands is high enough to impact hydraulic and mechanical properties during gas production fluid motion during gas production can mobilize fines which can then clog pore throats limiting production rates pore water freshening during gas hydrate dissociation can increase fines mobilization particularly given the smectite identified in the fine grained interbeds

seismic imaging of a fractured gas hydrate system in the krishna godavari basin offshore india gas hydrate was discovered in the krishna godavari kg basin during the india national gas hydrate program nghp expedition 1 at site nghp 01 10 within a fractured clay dominated sedimentary system logging while drilling lwd coring and wire line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500 m transect three dimensional 3d seismic data were subsequently used to image the fractured system and explain the occurrence of gas hydrate associated with the fractures a system of two fault sets was identified part of a typical passive margin tectonic setting the lwd derived fracture network at hole nghp 01 10a is to some extent seen in the seismic data and was mapped using seismic coherency attributes the fractured system around site nghp 01 10 extends over a triangular shaped area of 2 5 km2 defined using seismic attributes of the seafloor reflection as well as seismic sweetness at the base of the gas hydrate occurrence zone the triangular shaped area is also showing a polygonal nearly hexagonal fault pattern distinct from other more rectangular fault patterns observed in the study area the occurrence of gas hydrate at site nghp 01 10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source the triangular shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits additionally the fault associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone it is proposed that there are additional locations in the kg basin with possible gas hydrate accumulation of similar tectonic conditions and one such location was identified from the 3d seismic data 6 km nw of site nghp 01 10

gas hydrate distribution and carbon sequestration through coupled microbial methanogenesis and silicate weathering in the krishna godavari basin offshore india abstract the national gas hydrate program expedition 01 cored ten sites in the krishna godavari basin located on the southeastern margin of india a comprehensive suite of pore water solute concentrations and isotope ratios were analyzed to investigate the distribution and concentration of gas hydrate along the margin in situ diagenetic and metabolic reactions and fluid migration and flow pathways gas hydrate was present at all of the sites cored and in situ microbial methanogenesis leads to estimates of depth integrated average gas hydrate saturations that are typically

the use of mineral magnetic analyses in identifying middle and late holocene agriculture a study of peat profiles in smaland southern sweden a transect of profiles from the bratamossen bog near the village of axlarp in the province of smaland southern sweden was investigated with respect to magnetic properties human impact pollen indicators and loss on ignition the bog is situated close to an area with clearance cairns an indication of abandoned arable fields there are also graves from the bronze age and the early iron age close to the bog a variety of analytical methods were used to reconstruct the land use history of this area since c 6000 14 c years bp while pollen analysis was used to detect changes in vegetation the magnetic analyses reflected how the soils in the landscape were affected by these changes the pollen analysis showed that the area became deforested and that forest vegetation was succeeded by pasture and arable land magnetic analyses indicated soil erosion as a consequence of agricultural activity the conventional technique of determining the minerogenic content by loss on ignition yielded no valuable information

formation of methane related authigenic carbonates in a highly dynamic biogeochemical system in the krishna godavari basin bay of bengal abstract we report the abundant occurrence of authigenic fe rich carbonate high mg calcite hmc and low mg calcite from 11 cores recovered from the krishna godavari basin k g basin bay of bengal the cores were collected as part of the indian gas hydrate exploration program on board r v marion dufresne md 161 may 2007 in different environments including mounds mud diapirs mass flows and hemipelagic sediments over a range of water depths from 647 to 2079 m authigenic carbonates range in size from 1 mm to 12 cm and display various morphologies like roundish or platy micro nodules and tube like forms from the cores 173 carbonate samples have been investigated for their depth distribution mineralogy geochemical and stable isotopic composition the stable carbon isotopic composition of 46 out of 88 measured carbonate samples are around 50 which allows the differentiation into methane related carbonates hmc especially at sites 8 and 15 but also in low abundance at sites 1 5 9 and 12 results indicate that the carbonates at site 8 and 15 represent paleo methane seepage locations the fe rich carbonates occur abundantly at many sites in the k g basin their varying carbon isotopic composition indicates that probably not only sulfate reduction through organic matter degradation but also methanogenesis are the responsible processes for their formation

assessment of gas hydrate accumulations using velocities derived from vertical seismic profiles and acoustic log data in krishna godavari basin india abstract the second indian national gas hydrate program expedition nghp 02 was executed in 2015 in four areas termed as areas a b c and e during this expedition twenty five research sites were drilled and or cored in krishna godavari kg and mahanadi basins eastern indian offshore during nghp 02 zero offset vertical seismic profile vsp data were acquired at three sites sites nghp 02 17 19 and 22 in area b of the kg basin in this study we focus on the three sites in area b of the kg basin where zero offset vsp and downhole acoustic log data are used to assess and characterize the gas hydrate deposits zero offset vsp data are correlated with wireline log surface seismic and synthetic seismic data to characterize and delineate gas hydrate accumulations in the kg basin low velocities ranging from 1500 to 1650 m s are observed in the unconsolidated shallow sedimentary section above gas hydrate bearing units whereas very high velocities are observed in the acquired acoustic log and vsp data in the gas hydrate bearing sedimentary sections the vsp derived interval velocities range from 2000 to 3000 m s in the depth interval between 267 and 287 m below sea floor mbsf at site nghp 02 17 between 1650 and 1750 m s in the depth interval between 306 and 366 mbsf at site nghp 02 19 and between 1700 and 1800 m s in the depth interval between 198 and 290 mbsf at site nghp 02 22 gas hydrates are distributed both as pore filling and fracture filling at all three sites however high concentrations are only observed as pore filling morphology we estimate the amount of gas hydrate considering both isotropic pore filling and anisotropic fracture filling acoustic reservoir models our estimations of gas hydrate saturation match well with the available pressure core data and suggest that high gas hydrate concentrations to nearly 85 of pore space are distributed in a load bearing morphology

lithofacies characterization of gas hydrate prospects discovered during the national gas hydrate program expedition 02 offshore krishna godavari basin india abstract lithofacies of host sediments associated with gas hydrate reservoirs may have a significant influence on the formation of hydrates the type of sediments and the depositional processes responsible for the gas hydrate bearing sediments along the eastern margin of the india have been studied by integrating core data and logging while drilling downhole logs borehole data correlated with seismic data were used for the interpretation of geological process responsible for gas hydrate formation the acquired seismic profiles were correlated with the downhole logs by identifying the shape of the well logs curves that indicate finning up and blocky patterns turbidite sands and debris flows were also identified from the log and core sediment studies this study identified two prominent types of depositional systems 1 turbidity currents and 2 debris flows were mainly responsible for the deposition of gas hydrate bearing reservoirs in the study area based on these studies two well developed gas hydrate systems have been identified in the krishna godavari basin and hydrates were determined to be distributed mostly in sand dominated facies fine grained sand in the identified turbidite deposits were shown to be a good hydrate reservoir the hydrate bearing sediments in the central part of the krishna godavari basin area c in d6 block consist of mostly debris flows which is consistent with scattered gravel and sand silt sized grains in channel levee systems

geologic implications of gas hydrates in the offshore of india krishna godavari basin mahanadi basin andaman sea kerala konkan basin gas hydrate resource assessments that indicate enormous global volumes of gas present within hydrate accumulations have been one of the primary driving forces behind the growing interest in gas hydrates gas hydrate volumetric estimates in recent years have focused on documenting the geologic parameters in the gas hydrate petroleum system that control the occurrence of gas hydrates in nature the primary goals of this report are to review our present understanding of the geologic controls on the occurrence of gas hydrate in the offshore of india and to document the application of the petroleum system approach to the study of gas hydrates national gas hydrate program of india executed the national gas hydrate program expedition 01 nghp 01 in 2006 in four areas located on the eastern and western margins of the indian peninsula and in the andaman sea these areas have experienced very different tectonic and depositional histories the peninsular margins are passive continental margins resulting from a series of rifting episodes during the breakup and dispersion of gondwanaland to form the present indian ocean the andaman sea is bounded on its western side by a convergent margin where the indian plate lithosphere is being subducted beneath southeast asia nghp 01 drilled logged and or cored 15 sites 31 holes in the krishna godavari basin 4 sites 5 holes in the mahanadi basin 1 site 2 holes in the andaman sea and 1 site 1 hole in the kerala konkan basin holes were drilled using standard drilling methods for the purpose of logging while drilling and dedicated wireline logging as well as through the use of a variety of standard coring systems and specialized pressure coring systems nghp 01 yielded evidence of gas hydrate from downhole log and core data obtained from all the sites in the krishna godavari basin the mahanadi basin and in the andaman sea the site drilled in the kerala konkan basin during nghp 01 did not yield any evidence of gas hydrate most of the downhole log inferred gas hydrate and core recovered gas hydrate were characterized as either fracture filling in clay dominated sediments or as pore filling or grain displacement particles disseminated in both fine and coarse grained sediments geochemical analyses of gases obtained from sediment cores recovered during nghp 01 indicated that the gas in most all of the hydrates in the offshore of india is derived from microbial sources only one site in the andaman sea exhibited limited evidence of a thermogenic gas source the gas hydrate petroleum system concept has been used to effectively characterize the geologic controls on the occurrence of gas hydrates in the offshore of india