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Simon P. Holford - One of the best experts on this subject based on the ideXlab platform.
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the influence of reverse reactivated normal faults on porosity and permeability in sandstones a case study at castle cove Otway Basin
Exploration Geophysics, 2018Co-Authors: Natalie Debenham, Simon P. Holford, Rosalind King, Natalie Farrell, David HealyAbstract:An understanding of fault zone structure and transmissibility can have significant implications for reservoir appraisal and development within petroleum systems. Studies tend to focus on low porosity host rocks that have experienced simple tectonic histories while the influence of complex fault systems (that have undergone multiple phases of deformation) on porous rocks within fault damage zones have not been investigated. We present results from a detailed mineralogical and geomechanical investigation of the Castle Cove Fault within the Otway Basin at Castle Cove, southeast Australia. Castle Cove provides excellent exposures of the Lower Cretaceous Eumeralla Formation, which is a fine-grained volcanogenic sandstone with moderate to high porosity (up to 27%) and low permeability (mostly <1 mD). The Castle Cove Fault originated as a normal fault during the late Cretaceous and was reverse-reactivated during Miocene–Pliocene compression. Core plugs were sampled at distances between 0.5 to 225 m from the fault and were orientated with respect to the fault plane. We show that closer to the fault (within 75 m), porosity increases by nearly 10% (from approximately 17% to 24%) and permeability increases by two orders of magnitude (from 0.04 mD to 2.92 mD). Microstructural investigations from thin sections show an increase in microfracture intensities closer to the fault. Also observed is a change in the morphology of pore-lining chlorite, from well-structured away from the fault to broken up and disaggregated adjacent to the fault. This study highlights the importance of detailed mineralogical and petrophysical analyses when attempting to understand the reservoir properties of high porosity and low permeability sandstones.
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the influence of a reverse reactivated normal fault on natural fracture geometries and relative chronologies at castle cove Otway Basin
Journal of Structural Geology, 2018Co-Authors: Natalie Debenham, Rosalind King, Simon P. HolfordAbstract:Abstract Despite the ubiquity of normal faults that have undergone compressional inversion, documentation of the structural history of natural fractures around these structures is limited. In this paper, we investigate the geometries and relative chronologies of natural fractures adjacent to a reverse-reactivated normal fault, the Castle Cove Fault in the Otway Basin, southeast Australia. Local variations in strain resulted in greater deformation within the fault damage zone closer to the fault. Structural mapping within the damage zone reveals a complex tectonic history recording both regional and local perturbations in stress and a total of 11 fracture sets were identified, with three sets geometrically related to the Castle Cove Fault. The remaining fracture sets formed in response to local stresses at Castle Cove. Rifting in the late Cretaceous resulted in normal movement of the Castle Cove Fault and associated rollover folding, and the formation of the largest fracture set. Reverse-reactivation of the fault and associated anticlinal folding occurred during late Miocene to Pliocene compression. Rollover folding may have provided structural traps if seals were not breached by fractures, however anticlinal folding likely post-dated the main episodes of hydrocarbon generation and migration in the region. This study highlights the need to conduct careful reconstruction of the structural histories of fault zones that experienced complex reactivation histories when attempting to define off-fault fluid flow properties.
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determining paleo structural environments through natural fracture and calcite twin analyses a case study in the Otway Basin australia
The APPEA Journal, 2018Co-Authors: Hugo B Burgin, Khalid Amrouch, Mojtaba Rajabi, David Kulikowski, Simon P. HolfordAbstract:The structural history of the Otway Basin has been widely studied; however, previous works have focussed on large kilometre scale, Basin and seismic structures, or have over-simplified natural fracture analysis with an excessive focus on fracture strike direction and a disregard for 3D geometry, a crucial characteristic when considering states of stress responsible for natural fracture formation. In this paper, we combine techniques of natural fracture analysis and calcite twin stress inversion to investigate the meso (outcrop and borehole) and micro (crystal) scale evidence for structural environments that have contributed to Basin evolution. Our results indicate that Basin evolution during the post-Albian may be markedly more complex than the previously thought stages of late Cretaceous inversion, renewed rifting and long-lived mid-Eocene to recent compression, with evidence for up to six structural environments detected across the Basin, including; NE–SW and NW–SE extension, NW–SE compression, a previously undetected regime of NE–SW compression, and two regimes of strike-slip activity. By constraining structural environments on the meso- and micro-scale we can deliver higher levels of detail into structural evolution, which in turn, provides better-quality insights into multiple petroleum system elements, including secondary migration pathways and trap formation. Our research also shows that the Otway Basin presents a suitable environment for additional micro-scale structural investigations through calcite twin analyses.
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Structural evolution of horst and half-graben structures proximal to a transtensional fault system determined using 3D seismic data from the Shipwreck Trough, offshore Otway Basin, Australia
Marine and Petroleum Geology, 2018Co-Authors: A.g. Robson, R. C. King, Simon P. Holford, D. KulikowskiAbstract:Using a three-dimensional (3D) seismic reflection dataset from the Shipwreck Trough, offshore Otway Basin, southern Australia, we aim to characterise and understand the structural evolution of the Shipwreck Fault Zone (SFZ) and associated extensional structures. The SFZ is a key structural element of the Otway Basin, which is a NW striking, Upper Jurassic-Cenozoic, rift-to-passive margin Basin that formed due to the breakup of Australia and Antarctica. The SFZ marks the transition from the major southern margin rift system to the west and the oceanic-continental transform margin to the SE. The SFZ formed and bounds the Shipwreck Trough on the eastern side and is interpreted as a N–S striking transtensional fault zone, representing the northern en echelon extension of the transform margin to the south. The Shipwreck Trough is the downward thrown (western) side of the SFZ and is host to an array of horst and half-graben structures, two of which contain the producing Geographe and Thylacine gas fields. The Shipwreck Trough and SFZ are imaged by the Investigator 3D seismic dataset, which has previously been studied to conduct 2D restorations and interpret the timing, magnitude, orientation and nature of the structural events of the Shipwreck Trough. Our study adds to this previous research by using spectral decomposition and coherence volumes to further characterise the SFZ (and associated igneous features), basement structural elements and Late Cretaceous horst and half-graben structures. We have identified examples of releasing bend, releasing jog and restraining jog structures along the SFZ that are indicative of sinistral transtensional deformation and have highlighted areas of increased basement fault block relief, which have driven extensional faulting in the cover. We have also conducted throw-distance and throw-depth analysis on four horst and half-graben structures and shown that the associated normal faults have had continuous Late Cretaceous growth with the structures being formed through incidental linkage of normal fault segments. Finally, our two-way-time (TWT) and isochronal mapping of the entire 3D survey shows the development of the Late Cretaceous rifting event in the Shipwreck Trough and highlights numerous other structural closures similar to (and with close vicinity of) the Thylacine and Geographe gas fields, providing implications for prospectivity.
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The permeability structure of fault zones in sedimentary Basins: a case study at the Castle Cove Fault, Otway Basin
The APPEA Journal, 2018Co-Authors: Natalie Debenham, Simon P. Holford, Rosalind King, Natalie J. C. Farrell, David HealyAbstract:An understanding of the permeability structure and transmissibility of fault zones can have profound implications for reservoir appraisal and development within petroleum systems. Previous investigations on the permeability structure of fault zones often focus on low-porosity host rocks rather than porous sedimentary rocks which more commonly form reservoirs. We present detailed mineralogical and geomechanical data from porous Cretaceous sandstones (Eumeralla Formation) collected at the Castle Cove Fault in the Otway Basin, south-east Australia. Ten orientated sample blocks were collected in the hanging wall at distances within 0.5–225 m from the fault plane. A progressive increase in porosity (~17–24%), permeability (0.04–2.92 mD), and pore throat size and connectivity was observed as the fault plane was approached. High-resolution thin section analyses revealed an increase in grain-scale fractures and deformation of authigenic clays in sandstones adjacent to the Castle Cove Fault plane. The improvement of the permeability structure of the sandstones is attributed to the formation of grain-scale fractures and the change in clay morphology as a result of faulting. This study demonstrates the importance of detailed mineralogical and geomechanical analyses when attempting to understand the reservoir properties of high porosity, low permeability, and clay-rich sandstones.
Stephen J. Gallagher - One of the best experts on this subject based on the ideXlab platform.
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palaeobiogeographical affinities and palaeoceanographical significance of late cretaceous ostracoda crustacea from voluta 1 Otway Basin southeastern australia
Alcheringa, 2020Co-Authors: Mark T Warne, Stephen J. GallagherAbstract:A continental shelf to upper continental slope ostracod fauna is documented from the late Cretaceous (late Turonian to Santonian) Belfast Mudstone in Voluta-1 of the Otway Basin, southeastern Austr...
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palaeoenvironments and palaeocommunities from lower cretaceous high latitude sites Otway Basin southeastern australia
Palaeogeography Palaeoclimatology Palaeoecology, 2018Co-Authors: Annemarie P Tosolini, Stephen J. Gallagher, Vera A Korasidis, Barbara E Wagstaff, David J Cantrill, Martin S NorvickAbstract:Abstract Lower Cretaceous (Barremian to Albian) fossil plant assemblages are preserved in sediments of the Otway Group, Otway Basin, and contemporaneous Strzelecki Group, Gippsland Basin, southeastern Australia. Detailed lithofacies and biofacies analyses of terrestrial strata within the upper Eumeralla Formation (Albian), Otway Group, allow fine-scale interpretation of braided fluvial and paludal depositional environments throughout the succession. The previously described flora is re-assessed in light of changes in depositional style and plant communities to describe six Albian biofacies. Forests in the highlands are dominated by Araucariaceae conifers, which turn over to Podocarpaceae and Cheirolepidiaceae forests on the dry, raised areas in the lowlands. Ferns and angiosperms inhabit the moist floodplains and water ferns and lycophytes dwell in the ox-bow lakes. Significant changes occur between floral communities characteristic of riparian, levee and floodBasin settings through the Early Cretaceous. Albian floras are characterized by the dominance of broad-leafed araucarian conifers, an understory of diverse ferns and a dearth of seedferns and angiosperms. There is a notable absence of macrofossil ginkgoaleans in the Eumeralla Formation, although they reappear in younger (Turonian) deposits in southeastern Australia, but angiosperms are extremely scarce as macrofossils compared to the diversity recently recorded in the pollen record. Abundant charcoal demonstrates that fire continued to be a significant environmental factor at high latitudes during the middle to late Albian. The discovery of dinoflagellate species supports an earlier marine incursion and increased coastal environments, probably inhabited by cheirolepids, across the Otway Basin. Palaeontological, palynological and sedimentological data has provided a synthesis of the region's warm, high-latitude, palaeoclimatic setting in the Albian stage of the Early Cretaceous when compared to the cooler Barremian to Aptian.
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biostratigraphy and macroinvertebrate palaeontology of the petroleum rich belfast mudstone sherbrook group uppermost turonian to mid santonian Otway Basin southeastern australia
Cretaceous Research, 2009Co-Authors: Jeffrey D Stilwell, Stephen J. GallagherAbstract:The hydrocarbon-rich Turonian to Santonian Belfast Mudstone (Sherbrook Group) of the Otway Basin, southern Victoria, Australia, represents transgressive lower delta plain to prodelta conditions in inner to middle shelf depths to slope environments. Comprising relatively homogeneous mudstone that thickens to more than 1 km in the offshore Otway Basin, the biostratigraphic resolution has been enhanced by study here of both macro- and microfossil assemblages. Macrofossils consist of 12 species of bivalves from a relatively low diversity of genera (Nucula s.l., Nuculana, Mesosaccella, Pinna?, Tethyoceramus, Oistotrigonia), gastropods (Cerithioidea, Latiala, Ringiculidae), cephalopods (Eutrephoceras?, Borissiakoceras), and cnidarians (Trochocyathus (Platycyathus?)). Other invertebrate groups such as echinoids and serpulids are too poorly represented and preserved for description. New and probably new taxa described include the bivalve Oistrotrigonia austronana sp. nov. (Trigoniidae), Mesosaccella sp. nov.? (Nuculanidae) and ammonite Borissiakoceras sp. nov.? (Binneyitidae). The probable presence of the inoceramid bivalve and index taxon Tethyoceramus madagascariensis and binneyitid ammonite Borissiakoceras sp. nov.?, corroborated by known ranges of other macroinvertebrates and Foraminifera in the Belfast Mudstone from the offshore Otway Basin, constrain the age in cores 13 and 16 of the well Voluta-1 to the Coniacian Stage (probably equivalent to the Tethyoceramus madagascariensis Zone, lower part of Coniacian, ca. 89–88 Ma, for core 16 and late? Coniacian for core 13). All of the bivalves and gastropods are infaunal and/or semi-infaunal suspension and deposit feeders that preferred fine-grained facies, and these fossils and others support the interpretation of a low-energy hydrodynamic regime in a quiescent, deeper shelf setting.
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late cretaceous dysoxia in a southern high latitude siliciclastic succession the Otway Basin southeastern australia
Palaeogeography Palaeoclimatology Palaeoecology, 2005Co-Authors: Stephen J. Gallagher, Malcolm W. Wallace, G R Holdgate, Jeffrey D Stilwell, D H Taylor, M Apthorpe, C J Boreham, Patrick G QuiltyAbstract:The warm greenhouse world of the Late Cretaceous created oceans that were poorly stratified latitudinally and vertically. Periodically these oceans experienced globally significant events where oxygen minimum zones enveloped the continental margins. Evidence of the effect of one of these Ocean Anoxic Events (OAEs) is preserved in the southern high latitude strata of the offshore Otway Basin in southeast Australia. During the Late Cretaceous, thick successions (up to 6 km) of mudstonedominated deltaic to upper bathyal sediments (the Otway Delta) were deposited in an elongate inlet (ca. 500 km wide) between Antarctica and Australia located at least 708 S. The initial Turonian strata of this succession (the Waarre Formation) were deposited in upper delta plain to delta front conditions. The overlying late Turonian Flaxman Formation and basal Belfast Mudstone Formation preserve evidence of transgressive lower delta plain to prodelta conditions at inner to middle shelf depths. These units were subject to periodic dysoxia during deposition caused by intermittent freshwater input and deepening seas resulting in periods of thermohaline stratification and reduced bottom waters. Rapid subsidence from 89.3 Ma to 85.7 Ma created significant accommodation space leading to the seaward progradation of normal marine prodelta to upper bathyal mudstone-dominated facies at middle shelf to upper slope depths. After a period when the oxygen minimum zone contracted near the base of the Coniacian, upward-increasing dysoxia in the Belfast Mudstone Formation heralds the onset of Coniacian to Santonian dysoxic conditions. This event in the Otway Basin correlates to OAE 3, the last Ocean Anoxic Event of the warm Cretaceous before the onset of cooler conditions in the uppermost Cretaceous. The evidence suggests that, rather than confined to low latitude tropical areas, the effects of OAE 3 reached southern high latitude regions during the warm Late Cretaceous. The cessation of growth faulting after 85.7 Ma reduced accommodation space and delta front to prodelta facies prograded rapidly seaward. Hyposaline conditions and higher sedimentation rates due to delta front progradation and shallowing during this time
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marine clays and porosity evolution in the nullawarre greensand Otway Basin southeastern australia
PESA's Eastern Australasian Basins Symposium 11, 2004Co-Authors: G.a. Boyd, Guy R. Holdgate, Malcolm W. Wallace, Stephen J. GallagherAbstract:The Nullawarre Greensand of the Late Cretaceous Sherbrook Group, Otway Basin, has an unusual diagenetic history that has produced significant volumes of early marine clay minerals. Together with glauconite grains, siderite, carbonate fluor-apatite cements, and pyrite, the Nullawarre Greensand also contains the Fe-rich green clay mineral berthierine. Berthierine is present as concentric lamellae on ooid grains, as early-zoned, isopachous, fibrous cement, and as laterstage, unzoned cement. XRD analysis reveals that the berthierine has a weakly interstratified structure with chamosite, and this is consistent with estimated maximum palaeotemperatures for the Nullawarre Greensand of between 68‐85oC in the onshore Port Campbell Embayment region. Berthierine is the low-temperature precursor mineral to the iron-rich chlorite mineral chamosite, which is found to preserve porosity in high quality reservoir sands in the United States, off the coast of Norway, and in the North Perth Basin of Western Australia. Berthierine cements of the Nullawarre Greensand may have also preserved porosity by inhibiting the development of quartz overgrowths. The presence of berthierine ooids and cements also provides evidence that the Nullawarre Greensand was deposited in a shallow, near coastal environment during a period of reduced clastic sediment influx. It can be classed, in part, an ooidal facies.
Pierre Camps - One of the best experts on this subject based on the ideXlab platform.
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co2 percolation experiment through chlorite zeolite rich sandstone pretty hill formation Otway Basin australia
Chemical Geology, 2012Co-Authors: Linda Luquot, Muriel Andreani, Philippe Gouze, Pierre CampsAbstract:Underground CO2 sequestration is highly recommended as an effective means of significantly decreasing CO2 concentration in the atmosphere. Mineral storage is the more secure technology, but requires the presence of high concentration of divalent cations in the pore-fluid. Results from CO2 percolation experiments through chlorite/zeolite-rich sandstone samples from the Pretty Hill Formation (Otway Basin, Australia) are presented. The dissolution of the laumontite (7 wt.%) and chamosite (7 wt.%) are the potential sources of calcium, iron and magnesium required for carbonate precipitation. The percolation experiment was setup to reproduce, at laboratory scale, the in situ temperature and pressure conditions (T = 95 degrees C and P = 10 MPa). The fluid injected at constant flow rate is a rock-equilibrated brine subsequently enriched in CO2 up to partial pressure of 6 MPa. We observe feldspars, laumontite and chamosite dissolution, kaolinite and silica precipitation and a noticeable sink of CO2 in the sample which is attributed to the precipitation of both amorphous carbon due to the reduction of CO2 and Fe-rich carbonate. Permeability decreases of about one order of magnitude due to the localization of the kaolinite precipitation in the main flow paths, while porosity increases. The high reactivity of this sandstone makes this reservoir a valuable target for CO2 mineralization, but the associated permeability decrease may limit the injection rate and the spreading of the CO2 in the reservoir.
Boris Gurevich - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of acoustic responses on the injection of supercritical co2 into sandstones from the Otway Basin
Geophysics, 2013Co-Authors: Maxim Lebedev, Marina Pervukhina, Vassili Mikhaltsevitch, Tess Dance, Olga Bilenko, Boris GurevichAbstract:Quantitative knowledge of the acoustic response of rock from an injection site on supercritical CO2 (scCO2) saturation is crucial for understanding the feasibility of time-lapse seismic monitoring of CO2 plume migration. A suite of shaley sandstones from the injection interval of the CRC-2 well, Otway Basin, Australia is tested to reveal the effects of supercritical CO2 injection on acoustic responses. CO2 is first injected into dry samples, flushed out with brine and then injected again into brine-saturated samples. Such a suite of experiments allows us to obtain acoustic velocities of the samples for a wide range of CO2/brine saturations from 0% to 100%. On injection of scCO2 into brine-saturated samples, the rocks exhibit a decrease of compressional velocities by about 7% with the increase of CO2 saturation from 0% to a maximum of about 50%. Anisotropy of the shaley sandstones from the Otway Basin must be taken into account as the difference in the velocities normal and parallel to bedding is comparable with the perturbation due to CO2 injection and the samples of different orientations exhibit transition from Gassmann-Hill to Gassmann-Wood bound at different scCO2 saturations. Changes of the dry samples before and after the CO2 injection (if any) are not traceable by acoustic methods.
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experimental laboratory study on the acoustic response of sandstones during injection of supercritical co2 on crc2 sample from Otway Basin australia
Energy Procedia, 2013Co-Authors: Maxim Lebedev, Boris Gurevich, Marina Pervukhina, Tess Dance, Olga Bilenko, Vassili MikhaltsevichAbstract:Quantitative knowledge of the acoustic response of rock from an injection site on supercritical CO2 saturation is crucial for understanding the feasibility of time-lapse seismic monitoring of CO2 plume migration. A suite of shaley sandstones from the CRC-2 well, Otway Basin, Australia is tested to reveal the effects of supercritical CO2 injection on acoustic responses. The sandstone samples were cut in different directions with respect to a formation bedding plane and varied in porosities between 14% and 29% and permeabilities between 0.2 mD and 10,000 mD. Pore pressures and temperatures were varied from 4 MPa to 10 MPa, and 23°C to 45°C respectively to cover both vapour and supercritical regions of CO2 phase diagram. CO2 is first injected into dry samples, flushed out with brine and then injected again into brine saturated samples. Such experimental protocol allows us to obtain acoustic velocities of the samples for the wide range of CO2 saturations from 0 to 100%. On injection of supercritical CO2 (scCO2) into brine-saturated samples, they exhibit observable perturbation of ~7% of compressional velocities with the increase of CO2 saturation form 0% to maximum (~50%). Changes of the dry samples before and after the CO2 injection (if any) are not traceable by acoustic methods. An applicability of implementation of fluid substitution using Gassman theory for CRC2 well has been proved in the experiments. CO2 Residual saturation of about 50% was measured by monitoring of the volume of brine displaced from the sample and was independently confirmed by computer tomography (CT) imaging of the sample before and after experiments.
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seismic monitoring of co2 injection into a depleted gas reservoir Otway Basin project
73rd EAGE Conference and Exhibition - Workshops 2011, 2011Co-Authors: Milovan Urosevic, Roman Pevzner, V Shulakov, Anton Kepic, Eva Caspari, Sandeep Sharma, Boris GurevichAbstract:Within the Stage I of the Otway Basin Project, of the Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), approximately 65,000 tons of CO2/CH4 mix in the ratio of 80/20 was injected into the Waarre C formation (depleted Naylor gas reservoir) over the last two years. The CO2 was produced and transported from a nearby natural accumulation, via pipeline and injected into a sandstone reservoir. The use of depleted gas fields for CO2 storage as well as CO2-based enhanced gas recovery are of global importance. Thus, the CO2CRC Otway Basin Pilot Project provides important experience in establishing whether such scenarios can be monitored by geophysical techniques, in particular seismic time-lapse methodology. Indeed injection of CO2 into a depleted gas reservoir (within residual gas saturation window) does not present favourable conditions for the application of geophysical monitoring techniques. Numerical simulation of the CO2 injection process at Otway show that changes in elasticity of the reservoir rock will be quite small and difficult to monitor even with the most powerful time-lapse (TL) seismic methodologies. Consequently, the design and implementation of the monitoring program had to address these issues. The monitoring program had two objectives: (1) to ensure detection of possible gas leakages out of the reservoir into other formations and (2) to attempt to detect changes of seismic response due to CO2 injection into the reservoir. To increase the sensitivity of TL seismic we combined 3D VSP with 3D surface seismic. For a land seismic case, we achieved excellent repeatability with 3D time lapse surveys, which at the reservoir level produced normalised RMS difference values of about 20% for surface seismic and 10% for 3D VSP, respectively. The location of the time-lapse anomaly detected at the reservoir level is broadly consistent with CO2 flow simulations. However borehole seismic measurements showed that timelapse is very small to be reliably evaluated from repeated surface seismic measurements as the anomaly is of a similar magnitude to noise, making its unique attribution to the CO2 plume difficult. One of the important outcomes of these studies is evaluation of land time-lapse seismic capabilities. New understanding and new methodologies for assessment of 3D seismic data repeatability were developed during Otway Basin tests. This helped us understand and validate time-lapse signal form the reservoir. It also enabled us to demonstrate that quality of time-lapse land surveys can be high enough to be able to detect very small, up to five thousand tonnes, leakages which is of essential importance to any monitoring program as it provides possibility for rapid mitigation.
Sandeep Sharma - One of the best experts on this subject based on the ideXlab platform.
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seismic monitoring of co2 injection into a depleted gas reservoir Otway Basin project
73rd EAGE Conference and Exhibition - Workshops 2011, 2011Co-Authors: Milovan Urosevic, Roman Pevzner, V Shulakov, Anton Kepic, Eva Caspari, Sandeep Sharma, Boris GurevichAbstract:Within the Stage I of the Otway Basin Project, of the Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), approximately 65,000 tons of CO2/CH4 mix in the ratio of 80/20 was injected into the Waarre C formation (depleted Naylor gas reservoir) over the last two years. The CO2 was produced and transported from a nearby natural accumulation, via pipeline and injected into a sandstone reservoir. The use of depleted gas fields for CO2 storage as well as CO2-based enhanced gas recovery are of global importance. Thus, the CO2CRC Otway Basin Pilot Project provides important experience in establishing whether such scenarios can be monitored by geophysical techniques, in particular seismic time-lapse methodology. Indeed injection of CO2 into a depleted gas reservoir (within residual gas saturation window) does not present favourable conditions for the application of geophysical monitoring techniques. Numerical simulation of the CO2 injection process at Otway show that changes in elasticity of the reservoir rock will be quite small and difficult to monitor even with the most powerful time-lapse (TL) seismic methodologies. Consequently, the design and implementation of the monitoring program had to address these issues. The monitoring program had two objectives: (1) to ensure detection of possible gas leakages out of the reservoir into other formations and (2) to attempt to detect changes of seismic response due to CO2 injection into the reservoir. To increase the sensitivity of TL seismic we combined 3D VSP with 3D surface seismic. For a land seismic case, we achieved excellent repeatability with 3D time lapse surveys, which at the reservoir level produced normalised RMS difference values of about 20% for surface seismic and 10% for 3D VSP, respectively. The location of the time-lapse anomaly detected at the reservoir level is broadly consistent with CO2 flow simulations. However borehole seismic measurements showed that timelapse is very small to be reliably evaluated from repeated surface seismic measurements as the anomaly is of a similar magnitude to noise, making its unique attribution to the CO2 plume difficult. One of the important outcomes of these studies is evaluation of land time-lapse seismic capabilities. New understanding and new methodologies for assessment of 3D seismic data repeatability were developed during Otway Basin tests. This helped us understand and validate time-lapse signal form the reservoir. It also enabled us to demonstrate that quality of time-lapse land surveys can be high enough to be able to detect very small, up to five thousand tonnes, leakages which is of essential importance to any monitoring program as it provides possibility for rapid mitigation.
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seismic monitoring of co2 injection into a depleted gas reservoir Otway Basin pilot project australia
Energy Procedia, 2011Co-Authors: Milovan Urosevic, Roman Pevzner, Anton Kepic, Eva Caspari, Valeriya Shulakova, Sandeep SharmaAbstract:Abstract The use of depleted gas fields for CO 2 storage as well as CO 2 -based enhanced gas recovery are of global importance. Thus, the CO2CRC Otway Basin Pilot Project provides important experience in establishing whether such scenarios can be monitored by geophysical techniques, in particular seismic time-lapse methodology. Injection of CO 2 into a depleted gas reservoir (with residual gas in the Otway case) does not present favourable conditions for the application of geophysical monitoring techniques. Simulation of the CO 2 injection process at Otway shows that changes in elasticity of the reservoir rock will be quite small and difficult to monitor even with the most powerful time-lapse (TL) seismic methodologies. Consequently, the design and implementation of the monitoring program had to address these issues. To increase the sensitivity of TL seismic we combined 3D VSP with 3D surface seismic. For land seismic case, we achieved excellent repeatability with 3D time lapse surveys, which at the reservoir level produced normalised RMS difference values of about 20% for surface seismic and 10% for 3D VSP, respectively. Still due to very small time lapse signal, the primary use of 3D surface seismic was for assurance monitoring. Borehole seismic measurements confirmed that time-lapse is too small to be reliably estimated and analysed from repeated seismic measurements. Finally, post-injection reservoir simulation and accompanying seismic modelling suggest that a prolonged CO 2 /CH4 injection should produce only negligible change of the elastic properties of the Naylor reservoir.
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australia s first geosequestration demonstration project the co2crc Otway Basin pilot project
The APPEA Journal, 2007Co-Authors: Sandeep Sharma, Peter Cook, Thomas Berly, C AndersonAbstract:Geological sequestration is a promising technology for reducing atmospheric emissions of carbon dioxide (CO 2 ) with the potential to geologically store a significant proportion of Australia's stationary CO 2 emissions. Stationary emissions comprise almost 50% (or about 280 million tonnes of CO 2 per annum) of Australia's total greenhouse gas emissions. Australia has abundant coal and gas resources and extensive geological storage opportunities; it is therefore well positioned to include geosequestration as an important part of its portfolio of greenhouse gas emission mitigation technologies. The Cooperative Research Centre for Greenhouse Gas Technologies is undertaking a geosequestration demonstration project in the Otway Basin of southwest Victoria, with injection of CO 2 planned to commence around mid 2007. The project will extract natural gas containing a high percentage of CO 2 from an existing gas well and inject it into a nearby depleted natural gas field for long-term storage. The suitability of the storage site has been assessed through a comprehensive risk assessment process. About 100,000 tonnes of CO 2 is expected to be injected through a new injection well during a one- to two-year period. The injection of CO 2 will be accompanied by a comprehensive monitoring and verification program to understand the behaviour of the CO 2 in the subsurface and determine if the injected carbon dioxide has migrated out of the storage reservoir into overlying formations. This project will be the first storage project in Australia and the first in the world to test monitoring for storage in a depleted gas reservoir. Baseline data pertinent to geosequestration is already being acquired through the project and the research will enable a better understanding of long-term reactive transport and trapping mechanisms. This project is being authorised under the PetroleumAct 1998 (Victoria) and research, development and demonstration provisions administered by the Environment Protection Authority (EPA) Victoria in the absence of geosequestration-specific legislation. This highlights the need for such legislation to enable commercial-scale projects to proceed. Community acceptance is a key objective for the project and a consultation plan based on social research has been put in place to gauge public understanding and build support for the technology as a viable mitigation mechanism.
