Palaeo‐formation water evolution in the Latrobe aquifer, Gippsland Basin, south‐eastern Australia continental shelf

Salinity of fluid inclusions is usually determined by microthermometry, but it becomes unsuitable in case of metastability of the aqueous fluid because of thermodynamics indetermination. Raman microspectrometry of water in individual aqueous fluid inclusions can provide chemical information about fluid composition, in particular the concentration of chloride ions. The regular method consists in correlating the deformation of the OH stretching vibration band of liquid water in the region assigned to hydrogen‐bonded OH groups, with chloride concentration. In order to evaluate the ability of Raman spectroscopy to determine salinity of metastable fluid inclusions, the Raman spectra of water trapped in two natural fluid inclusions were recorded at various temperatures in two physical states of the liquid phase, at equilibrium with vapor or metastable at negative pressure. The difference in salinity measured in the two states increased when temperature decreased, i.e. when the intensity of metastability increased. Metastability was then expressed in negative pressure scale (MPa) by thermodynamic modeling of the fluid trapped in the inclusions and correlated to salinity relative difference. The quantification of this effect led us to conclude that salinity expressed in mass% NaCleq. was overestimated of about 1% per 10–15 MPa of negative pressure. If the negative pressure can be quantified, it is thus possible to determine the salinity of metastable fluid inclusions by Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.

A new technique has been developed that allows determination of the resistivity of a pristine sample of irreducible water trapped during oil accumulation, This fluid inclusion technique, termed ROI, is directly applicable to the evaluation of oil accumulations where the salinity of present day formation waters below the OWC differs from that of irreducible water trapped during oil accumulation. Determination of oil saturation for calculation of oil reserves is critically dependent on the resistivity of formation water (Rw). Water saturations calculated from logs require an Rw value for irreducible water in the oil zone. In conventional log analysis the formation water salinity in the oil zone and therefore the Rw is assumed to be the same as that below the OWC. This relies on the assumption that the water below the OWC has not changed following oil charge. Irreducible water is trapped with oil in microscopic fluid inclusions within reservoir grains. Resistivity of this water can be derived from an ice melting temperature using the correlation between colligative and transport properties of aqueous solutions. Measurements are made on core or cuttings samples from the oil zone and exclude contamination from mud filtrate invasion. Introduction Water below the OWC may change after oil charge in basins which are exposed at the land surface. This may allow recharge of meteoric water, potentially resulting in lower salinity water below the OWC than in the oil zone e.g. in more shoreward oil filled reservoirs underlain by freshwater aquifers in the Gippsland Basin, calculated water saturations using the salinities from water below the OWC are inconsistent with RFT, capillary pressure and production test data. The opposite situation can also occur where tectonic movements cause relatively deep saline water to flow into reservoir rocks below the OWC. In these situations the water below the OWC will differ in salinity and Rw from irreducible water in the oil zone which is shielded from later flow of formation water by high oil saturation. The timing of changes in hydrology relative to oil charge has major implications because use of an inappropriate formation water resistivity value can result in incorrect reserves estimation. Decisions regarding field development are linked to reserves estimates and accurate Rw values are essential. Current Methods for Determination of Rw The most direct way of finding water resistivity (Rw) is to obtain a sample of formation water and measure its resistivity. However, this is seldom possible, as formation water samples are usually contaminated by mud filtrate. Rw is therefore usually calculated by one of two methods:SP methodArchie equation Reliable determination of oil saturation from logs requires a determination of Rw from a measurement directly on a sample of the irreducible water. Calculated Rw relies on a number of assumptions which may result in erroneous values - the SP method does not work for oil based muds and does not give correct estimations of Rw in hydrocarbon bearing zones while the Archie equation method only works in clean, water-bearing reservoirs and is typically unreliable in highly fractured or vuggy reservoirs. Capillary Pressure and Relative Permeability For practical purposes, the value of the irreducible or minimum water saturation in the oil zone is usually assumed to represent the interstitial water content of the pay section of the reservoir. Interstitial water in this zone is held in place by capillary forces, and flow differentials will not remove it. P. 137

Two different types of hydrogen in hydrothermal quartz from the Koryu deposit were distinguished by measurement of hydrogen isotope ratios and unpolarized and polarized infrared absorption spectra at room temperature and at -150 degrees C. The results of these measurements suggest that the hydrogen species in the hydrothermal quartz are liquid water (H 2 O) in fluid inclusions, silanol-type OH in the crystal structure of quartz, and liquid water in nanometer-sized domains of water molecules. Among them, the liquid water in liquid domains is most abundant. The hydrogen isotope ratio of liquid water in liquid domains is 40 per mil lower than that of water in fluid inclusions. This implies that a large amount of silanol OH was incorporated into the quartz during the rapid crystal growth stage and liquid domains of nanometer size were then formed in the quartz during subsequent hydrothermal activity and cooling. The water extracted between 300 degrees and 500 degrees C yields the delta D value of the hydrothermal solution associated with quartz precipitation.

The Pasto Bueno tungsten-base metal ore deposit is situated at an elevation of nearly equal 4,000 meters in the north-central Andes of Peru. Mineralization occurs in near-vertical quartz vein systems that span several hundred meters on either side of the upper intrusive contact of a 9.5-m.y.-old quartz monzonite stock emplaced in a Jurassic-Cretaceous shale and quartzite sequence. The stock exhibits four pervasive and roughly zoned alteration assemblages from core to periphery: (1) alkalic, (2) phyllic-sericitic, (3) argillic, and (4) propylitic. Greisen assemblages of zinnwaldite, fluorite, pyrite, and minor topaz and tourmaline occur within the phyllic zone.The principal vein minerals are wolframite, tetrahedrite/tennantite, sphalerite, galena, and pyrite in a gangue of quartz, fluorite, sericite, and carbonate. Detailed studies of the hydrothermal mineral paragenesis established three major recognizable divisions: Greisen (60 to 70 percent of deposition), Vein (25 to 35 percent of deposition), and Vug ( 40 equivalent weight percent NaCl), high-temperature (400 degrees to 500 degrees C) solutions of magmatic derivation. The subsequent main Vein stage ore fluids attained a temperature range of 175 degrees to 290 degrees C and a salinity range of 2 to 17 equivalent weight percent NaCl. Boiling of the ore solutions is indicated only for the Greisen and early Vein stages of hydrothermal activity.The results of stable isotope studies on water in primary fluid inclusions indicate that the delta D (sub H 2 O) of the ore fluids varied from -29 per mil to -88 per mil (SMOW). Analyses of water contained in secondary inclusions indicate the delta D (sub H 2 O) of the fluids attained values as low as -145 per mil prior to the cessation of hydrothermal activity. The delta 18 O (sub H 2 O) of the hydrothermal fluids, as calculated from the delta 18 O quartz and carbonate data and the temperature data, range from +7.8 per mil to +0.0 per mil (SMOW). The delta D value of present-day meteoric water is --96 per mil.The patterns for delta D (sub H 2 O) and delta 18 O (sub H 2 O) values of the hydrothermal fluids indicate that mixing of a meteoric and possibly a metamorphic or other water component with water of magmatic derivation occurred during Vein stage deposition. Major variations in the deuterium content of the ore solutions are not reflected by fluctuations in the 18 O content, indicating that meteoric water circulated deep into the hydrothermal plumbing system. Wolframite deposition was associated with episodes of meteoric water influx that are reflected in the temperature, salinity, and delta D values of the water in fluid inclusions. Sulfide mineralization, on the other hand, was associated with water of magmatic derivation.The delta 13 C data for hydrothermal CO 2 range from --4.1 per mil to -11.9 per mil (PDB) and are interpreted to indicate that the carbon in the ore fluids was derived from both sedimentary and deep-seated sources. delta 34 S values of pyrite data exhibit a narrow range of values (-2.5 per mil to +3.9 per mil) with an average of +0.6 per mil, indicating that the sulfur was derived from a deep-seated or mantle source.Most of the components present in the Pasto Bueno ore deposits appear to be of magmatic origin. Clearly however, significant volumes of meteoric water and possibly other water were involved in some stages of the ore deposition process.

<p>Vein-hosted fluid inclusions may represent remnants of subsurface paleo-fluids and therefore provide a valuable record of fracture-controlled fluid flow. Isotope data (δ<sup>2</sup>H and δ<sup>18</sup>O) of fluid inclusions are particularly useful for studying the provenance and type of paleo-fluids circulating in the subsurface. Although isotopic analysis of sub-microliter amounts of fluid inclusion water is not straightforward, major steps forward have been made over the past decade through the development of continuous-flow set-ups. These techniques make use of mechanical crushing at a relatively low-temperature (110˚C) and allow for on-line analysis of both δ<sup>2</sup>H and δ<sup>18</sup>O ratios of bulk fluid inclusion water. However, continuous-flow techniques have mostly been used in speleothem research, and have not yet found a widespread application on vein systems for hydrogeological reconstructions.</p><p>We used isotope data of fluid inclusions hosted in calcite vein cements to reconstruct regional fluid migration pathways in the Albanian foreland fold-and-thrust system. Tectonic forces during thrust emplacement typically instigate distinct phases of fracturing accompanied by complex fluid flow patterns. The studied calcite veins developed in a sequence of naturally fractured Cretaceous to Eocene carbonate rocks as a result of several fracturing events from the early stages of burial onward. Fluid inclusion isotope data of the veins reveal that fluids circulating in the carbonates were derived from an underlying reservoir, which consisted of a mixture of meteoric water and evolved marine fluids, probably derived from deep-seated evaporites. The meteoric fluids infiltrated in the hinterland before being driven outward into the foreland basin. The fluid inclusion isotope data furthermore show that meteoric water becomes increasingly dominant in the system through time as migration pathways shortened and marine formation fluids were progressively flushed out.</p><p>The diagenetic stability of fluid inclusions is of key interest in the study of their isotope ratios. Recrystallization, secondary fluid infiltration and isotope exchange processes could potentially drive alterations of fluid inclusion isotope signatures after entrapment. In this case, however, isotope signatures of fluid inclusions seem to have remained largely unaltered, despite the Cretaceous to Tertiary age of the vein system. Oxygen isotope exchange processes between the fluid inclusion water and host mineral could have been inhibited at the relatively low temperatures of vein formation (i.e. <80˚C). Although more research into the diagenetic stability of fluid inclusion isotope ratios is required, the fluid inclusion isotope record has potential as a powerful tool for fluid provenancing in subsurface fluid flow systems.</p>

Hydrothermal alteration and fluid chemistry data of the early Cretaceous Endako porphyry molybdenum deposit, British Columbia, provide new information on the hydrothermal fluids associated with low-fluorine molybdenite mineralization. Molybdenite mineralization and hydrothermal alteration occur as early quartz ± molydenite stockwork veins with K feldspar-bearing selvages and paragenetically later quartz-molybdenite ribbon veins with sericite-bearing selvages. Late hydrothermal alteration is associated with the development of kaolinite and postore (Tertiary age) calcite veins. Fluid inclusions in early-formed quartz ± molybdenite stockwork veins with K feldspar-bearing alteration assemblages are dominated by moderate-salinity (5 to 15 wt % NaCl equiv), liquid-rich (type 1) and rare high-salinity (30 to 45 wt % NaCl equiv), halite-bearing (type 3) fluid inclusions. Type 1 and type 3 fluid inclusions in early veins homogenize between 390° and 430°C and 375° and 420°C, respectively. Secondary fluid inclusions (type 2) of low salinity (1 to 5 wt % NaCl equiv) in these early veins are minor, and homogenize between 130° and 285°C. Fluid inclusions in quartz-molybdenite ribbon veins with sericite-bearing alteration assemblages are dominated by moderate-salinity, liquid-rich (type 1) inclusions, with minor type 2 fluid inclusions. Type 1 fluid inclusions of ribbon veins homogenize between 360° and 400°C. Fluid inclusions in postore calcite veins are of only type 2 fluid inclusions, which homogenize at 209°C. Hydrothermal fluids recorded by type 1 and type 3 fluid inclusions in early veins were trapped under lithostatic to hydrostatic conditions between 0.3 and less than or equal to 2.0 kbar, and 360° and 560°C. Postore fluids recorded by type 2 fluid inclusions were trapped under conditions less than or equal to 0.5 kbar, and between 190° and 300°C. Quartz stockwork and ribbon veins possess δ 18O values of 8.4 ± 0.2 ( n = 9) and 8.4 ± 0.6 ( n = 13), respectively. Hydrothermal K feldspar and biotite from K feldspar alteration assemblages possess δ 18O values of 6.8 ± 0.4 ( n = 7) and 3.5 ± 0.8 ( n = 8), respectively. Oxygen isotope geothermometry of quartz-biotite and quartz-K feldspar pairs from K feldspar alteration assemblages yield temperatures between 200° and 490°C, which is similar to the trapping temperatures of hydrothermal fluids determined from fluid inclusion studies associated with molybdenite mineralization, the development of kaolinite, and calcite veins. The oxygen isotope temperatures of the quartz-biotite and quartz-K feldspar pairs suggest that K feldspar and biotite either record the approximate 18O composition of hydrothermal fluids associated with K feldspar alteration or have undergone 18O exchange with late-stage hydrothermal fluids. Hydrogen isotope composition of quartz stockwork and ribbon veins fluid inclusion waters range between –105 and –173 per mil. Solute chemistry studies of fluid inclusion waters indicate that ore-forming fluids from Endako have low Br/Cl and Br/Na ratios, and high I/Cl and I/Br ratios in comparison to Porgera (epithermal), Babine Lake (porphyry Cu), and St. Austell, Capitan Pluton (vein) deposits associated with magmatic processes. Na/K ratios of fluid inclusion waters yield temperatures (308° to 429°C) similar to those determined from type 1 and type 3 fluid inclusions and stable isotope thermometry. Results from fluid inclusion and solute chemistry studies indicate the involvement of hydrothermal fluids exsolved from a crystallizing melt in the formation of the Endako molybdenum deposit. However, oxygen and hydrogen isotope values deviate from the generally accepted magmatic compositions, which suggests the early involvement of meteoric water in the ore-forming fluids and ore genesis.

Raman microspectrometry of water in individual aqueous fluid inclusions can provide chemical information about fluid composition, in particular the concentration of chloride ions. The regular method consists in correlating the deformation of the OH stretching vibration band of liquid water in the region assigned to hydrogen‐bonded OH groups with chloride concentration. In the present study, a set of seven different minerals with various birefringence properties (barite, calcite, celestine, fluorite, kyanite, quartz and siderite) was selected for the analysis of the water band of their hosted aqueous fluid inclusions. The comparison with microthermometry highlighted that any birefringent mineral may affect the determination of salinity carried out by the analysis of the Raman signal of water: the Raman salinity exposed sinusoidal variations when rotating the samples on the microscope stage. This phenomenon was explained by mineral birefringence, and by the polarization properties of the OH stretching vibration band of liquid water and of the spectrometers gratings. A good knowledge of the polarization properties of the optical devices of the Raman spectrometer and a correct positioning of the sample thus result in salinity (chloride concentration) measurements with the same accuracy as classic microthermometry. Copyright © 2015 John Wiley & Sons, Ltd.

PreviousNext You have accessInternational Conference and Exhibition, Melbourne, Australia 13-16 September 20153-D Mapping and Correlation of Intraformational Seals Within the Latrobe Group in the Nearshore Gippsland BasinAuthors: Nick Hoffman*Tom EvansNatt ArianNick Hoffman*The CarbonNet Project, Victorian State Department of Economic Development, Melbourne, Victoria, Australia.Search for more papers by this author, Tom EvansThe CarbonNet Project, Victorian State Department of Economic Development, Melbourne, Victoria, Australia.Search for more papers by this author, and Natt ArianThe CarbonNet Project, Victorian State Department of Economic Development, Melbourne, Victoria, Australia.Search for more papers by this authorhttps://doi.org/10.1190/ice2015-2209988 SectionsAbout ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract During its assessment of the nearshore Gippsland Basin (within 25 km of the coastline), the CarbonNet project has identified interbedded coals and shales of the Middle Eocene Lower N. asperus Zone as the key seal for upper Halibut reservoirs. This interval corresponds to the (Bartonian) T2 basal zone of the coal seams within the onshore coal-bearing Traralgon Formation which is widespread within the nearshore region of the Gippsland Basin. Previous hydrocarbon exploration shows that the T2 sequence is the intraformational topseal to several intra-Latrobe oil accumulations in the nearshore area, and that distinct pressure and salinity differences exist across this aquitard. Hence, the T2 represents a sub-regional seal, and is shown to be one of a set of backstepping subregional seals throughout the Bass Strait petroleum province. This family of seals offers additional trapping opportunities for future oil exploration in the offshore Gippsland Basin. A detailed correlation between nearshore and onshore wells has been carried out using existing well and 3D seismic data to define 3D geometry and continuity of the T2 units. The onshore Traralgon Formation ties to the offshore Burong Formation in the Barracouta gas field and small oilfields in the nearshore western Gippsland Basin. Seismic attribute extracts are presented as maps of coal quality and facies demonstrating the aspect ratio and lateral extent of coal depocentres, as well as details of the fluvial inputs, channel geometries, and clastic depocentres. Seal capacity of these intraformational seals is defined as a minimum by the observed hydrocarbon columns but also by MICP data which suggests seal potential well in excess of the proven columns. The critical constraints on trap capacity appear to be fault-related, and depend on the time scale. For petroleum, where multi-million year trapping is required in order for oil to be still present today, very efficient trapping is required with essentially no fault transmissibility. For CO2 storage over many thousands of years, slow seepage through faults and offset baffles may be acceptable, especially where it leads to additional dissolution into the active aquifer which is sweeping fluids from onshore to offshoreCorrelation of the T2 sequence and the definition of fairways where there is suitable seal potential is crucial to assess CO2 storage potential and intraformational hydrocarbon trapping over the next 50 years of Gippsland Basin activity. Keywords: 3D, mapping, correlation, Gippsland BasinPermalink: https://doi.org/10.1190/ice2015-2209988FiguresReferencesRelatedDetailsCited byUsing External Peer Review to Build Confidence of the Pelican Storage SiteSSRN Electronic JournalSuccessful appraisal of the CarbonNet Pelican CO2 offshore storage siteSSRN Electronic Journal, Vol. 390The CarbonNet appraisal well for the Pelican CO2 offshore storage siteSSRN Electronic Journal, Vol. 390Probabilistic Approach to CO2 Plume Mapping for Prospective Storage Sites: The CarbonNet ExperienceEnergy Procedia, Vol. 114 International Conference and Exhibition, Melbourne, Australia 13-16 September 2015ISSN (online):2159-6832Copyright: 2015 Pages: 564 publication data© 2015 Published in electronic format with permission by the Society of Exploration Geophysicists and the American Association of Petroleum GeologistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 16 Sep 2015 CITATION INFORMATION Nick Hoffman*, Tom Evans, and Natt Arian, (2015), "3-D Mapping and Correlation of Intraformational Seals Within the Latrobe Group in the Nearshore Gippsland Basin," SEG Global Meeting Abstracts : 271-271. https://doi.org/10.1190/ice2015-2209988 Plain-Language Summary Keywords3DmappingcorrelationGippsland BasinLoading ...

Preservation ofδ 18O values of fluid inclusion water in quartz over geological time in an epithermal environment: Beregovo deposit, Transcarpathia, Ukraine

Sandstone Diagenesis in the Mount Isa Basin: An Isotopic and Fluid Inclusion Perspective in Relationship to District-Wide Zn, Pb, and Cu Mineralization

The evolution of aqueous–carbonic fluids in the Amba Dongar carbonatite, India: implications for fenitisation

The main objectives of this project were to investigate the potential impacts of CO2 geological storage in the near-shore area of the Gippsland Basin in southeast Australia on formation water displacement, pressure evolution, offshore petroleum fields, onshore water levels and salinity in the Latrobe aquifer. Another aspect was to characterise the evolution of the low-salinity wedge in the Latrobe aquifer. The investigation included fluid inclusion work, analysis of present-day formation water and numerical flow simulations. Onshore, production-induced pressure declines on the order of 100 kPa over a period of 42 years show negligible and only localized impacts on the salinity distribution in the Latrobe aquifer in the simulations. While injection of CO2 only results in a slight pressure increase in the onshore area, this increase may be considered advantageous because it would counteract the recent trend of underpressuring in the Gippsland Basin. For example, CO2 geological storage could be of benefit to the petroleum industry in the Gippsland Basin by providing pressure support for declining reservoirs as long as an appropriate injection strategy avoids contamination of petroleum fields still under production.

The stratiform Century Zn-Pb deposit and the discordant Zn-Pb lode deposits of the Burketown mineral field, northern Australia, host ore and gangue minerals with primary fluid inclusions that have not been affected by the Isan orogeny, thus providing a unique opportunity to investigate the nature of the ore-forming brines. All of the deposits are hosted in shales and siltstones belonging to the Isa superbasin and comprise sphalerite, pyrite, carbonate, quartz, galena, minor chalcopyrite, and minor illite. According to Pb model ages, the main ore stage of mineralization at Century formed at 1575 Ma, some 20 m.y. after deposition of the host shale sequence. Microthermometry on undeformed, primary fluid inclusions hosted in porous sphalerite shows that the Zn at Century was transported to the deposit by a homogeneous, Ca 2+ - and Na + -bearing brine with a salinity of 21.6 wt percent NaCl equiv. δD fluid of the fluid inclusion water ranges from −89 to −83 per mil, consistent with a basinal brine that evolved from meteoric water. Fluid inclusion homogenization temperatures range between 74° and 125°C, which are lower than the 120° to 160°C range calculated from vitrinite reflectance and illite crystallinity data from the deposit. This discrepancy indicates that mineralization likely formed at 50 to 85 Mpa, corresponding to a depth of 1,900 to 3,100 m. Transgressive galena-sphalerite veins that cut stratiform mineralization at Century and breccia-filled quartz-dolomite-sphalerite-galena veins in the discordant Zn-Pb lodes have Pb model ages between 1575 and 1485 Ma. Raman spectroscopy and microthermometry reveal that the primary fluid inclusions in these veins contain Ca 2+ , Na + , but they have lower salinities between 23 and 10 wt percent NaCl equiv and higher δD fluid values ranging from −89 to −61 per mil than fluid inclusions in porous sphalerite from Century. Fluid inclusion water from sphalerite in one of the lode deposits has δ 18 O fluid values of 1.6 and 2.4 per mil, indistinguishable from δ 18 O fluid values between −0.3 to +7.4 per mil calculated from the isotopic composition of co-existing quartz, dolomite, and illite. The trend toward lower salinities and higher δD fluid values relative to the earlier mineralizing fluids is attributed to mixing between the fluid that formed Century and a seawater-derived fluid from a different source. Based on seismic data from the Lawn Hill platform and paragenetic and geochemical results from the Leichhardt River fault trough to the south, diagenetic aquifers in the underlying Calvert superbasin appear to have been the most likely sources for the fluids that formed Century and the discordant lode deposits. Paragenetically late sphalerite and calcite cut sphalerite, quartz, and dolomite in the lode deposits and contain Na + -dominated fluid inclusions with much lower salinities than their older counterparts. The isotopic composition of calcite also indicates δ 18 O fluid from 3.3 to 10.7 per mil, which is larger than the range obtained from synmineralization minerals, supporting the idea that a unique fluid source was involved. The absolute timing of this event is unclear, but a plethora of Pb model, K-Ar, and 40 Ar/ 39 Ar ages between 1440 and 1300 Ma indicate that a significant volume of fluid was mobilized at this time. The deposition of the Roper superbasin from ca. 1492 ± 4 Ma suggests that these late veins formed from fluids that may have been derived from aquifers in overlying sediments of the Roper superbasin. Clear, buck, and drusy quartz in veins unrelated to any form of Pb-Zn mineralization record the last major fluid event in the Burketown mineral field and form distinct outcrops and ridges in the district. Fluid inclusions in these veins indicate formation from a low-salinity, 300° ± 80°C fluid. Temperatures approaching 300°C recorded in organic matter adjacent to faults and at sequence boundaries correspond to K-Ar ages spanning 1300 to 1100 Ma, which coincides with regional hydrothermal activity in the northern Lawn Hill platform and the emplacement of the Lakeview Dolerite at the time of assemblage of the Rodinia supercontinent.

Contrasting paleofluid systems in the continental basement: a fluid inclusion and stable isotope study of hydrothermal vein mineralization, Schwarzwald district, Germany

Evidence for a nonmagmatic component in potassic hydrothermal fluids of porphyry cu-Au-Mo systems, Yukon, Canada