Comparison of Maturation Data and Fluid-Inclusion Homogenization Temperatures to Simple Thermal Models

1997 ◽  
pp. 13-27
Author(s):  
K. David Newell
Keyword(s):  
Fluid Inclusion ◽  
Vitrinite Reflectance ◽  
Geothermal Gradient ◽  
Upper Ordovician ◽  
Thermal Event ◽  
Geothermal Gradients ◽  
Thermal Maturation ◽  
Tectonic History ◽  
History Of ◽  
Homogenization Temperatures

Time-temperature index (TTI) modeling is used to establish a simple theoretical thermal maturity for Paleozoic strata in central Kansas. These thermal maturation calculations are based on estimates of likely geothermal gradients and best knowledge of the tectonic history of the region, as derived from stratigraphic thicknesses and estimates of erosion at unconformities. Major uncertainties in the data for the TTI modeling are burial during Cretaceous time and geothermal gradient, thus several models were calculated in which ranges of these two variables were considered. Results of the thermal modeling are then compared to available data on the thermal maturation. These data are principally derived from subsurface samples, on which vitrinite-reflectance, pyrolysis, and fluid-inclusion analyses have been performed. Vitrinite-reflectance and Rock-Eval maturation measurements indicate that Middle and Upper Ordovician strata (i.e., Simpson, Viola, and Maquoketa formations) in the study area are in initial phases of oil generation. Maturation modeling can match the results of the organic analyses, but geothermal gradients and burial during the Cretaceous have to be maximized. Although the TTI modeling utilizing very high geothermal gradients and near-excessive thicknesses of Cretaceous strata can match the observed maturation, the modeled results are probably not correct because fluid-inclusion data from saddle dolomites from the Upper Ordovician Viola Limestone indicate this unit reached temperatures 50° C higher than the maximum modeled temperature. A thermal event is inferred to account for the excess maturation and elevated fluid-inclusion homogenization temperatures. This thermal event may be manifested in the erratic increase of vitrinite-reflectance with depth for post-Devonian strata, as well as for pyrolysis measurements in wells for which maturation profiles are available. Flow of heated water onto the cratonic shelf out of the Anadarko basin during the late Paleozoic Ouachita orogeny may be responsible for the maturation anomalies.

Clumped isotope geothermometry of an Ordovician carbonate mound, Hudson Bay Basin

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-102
Author(s):  
Josué J. Jautzy ◽  
Martine M. Savard ◽  
Denis Lavoie ◽  
Omid H. Ardakani ◽  
Ryan S. Dhillon ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Oil And Gas ◽  
Fission Track ◽  
Hudson Bay ◽  
Apatite Fission Track ◽  
Burial Diagenesis ◽  
Carbonate Mound ◽  
History Of ◽  
Homogenization Temperatures ◽  
Clumped Isotope

The Hudson Bay sedimentary basin was overlooked geologically until two decades ago. Recent efforts to understand the palaeogeothermal history of this basin have led to the evaluation of fluid inclusion microthermometry, apatite fission track, organic matter reflectance and Rock–Eval analyses. Although apatite fission track and organic maturity indicators tend to show relatively low maximum burial temperatures (60–80°C), evidence of potential oil slicks on the sea surface and oil and gas shows in offshore wells have been reported across Hudson Bay. Fluid inclusion microthermometry in a carbonate mound sequence suggests homogenization temperatures of 118 ± 25 and 93 ± 10°C for recrystallized synsedimentary marine calcite and late pore-filling burial calcite, respectively. This sequence provides an interesting geological framework to test the application of clumped isotope thermometry against independent geothermometers. Here, we present clumped isotope data acquired on the late calcite cements and diagenetically altered early marine phases. The integration of clumped isotopic data with other thermal indicators allows the reconstruction and refinement of the thermal–diagenetic history of these carbonates by confirming an episode of heating, probably of hydrothermal origin and prior to normal burial diagenesis, that reset both fluid inclusions and the clumped isotope indicators without recrystallization.

Genesis of the Pb–Zn deposit at Sant’Antonio di Val D’Aspra, Southern Tuscany (Italy): disparity between geo-petrographic data and fluid inclusion microthermometry

1990 ◽  
Vol 54 (375) ◽  
pp. 289-294 ◽  
Author(s):  
M. Giamello ◽  
F. Riccobono ◽  
G. Sabatini
Keyword(s):  
Fluid Inclusion ◽  
Carbonate Rocks ◽  
Fluid Inclusion Study ◽  
Mississippi Valley ◽  
Ore Minerals ◽  
Inclusion Study ◽  
History Of ◽  
Homogenization Temperatures ◽  
The One ◽  
Internal Sediments

AbstractThe Pb–Zn deposit at Sant'Antonio di Val d'Aspra in the Farma Valley (Southern Tuscany) is hosted by Lower Moscovian carbonate rocks and shows many characters commonly found in Mississippi Valley type (MVT) deposits. Ore minerals (essentially sphalerite and galena) are closely confined to dolomitized portions of an only partly preserved black limestone. Mineralized carbonate rocks appear to have been eroded before the deposition of the overlying Upper Moscovian (Late Podolskian) shales. The diffuse presence of structures frequently found in internal sediments of karstic cavities indicates that supergene mechanisms have played an important role in the history of the deposit. A fluid inclusion study carried out on ore and gangue minerals revealed the presence of two different types of inclusions. The homogenization temperatures ranged from 120°C to 225°C but the most frequently found values were around 170°C. Salinity ranged from moderately low values up to 20 eq. wt. % NaCl. Lead isotopic composition rules out any relationship between the Sant'Antonio mineralization and Tertiary hydrothermal base metal occurrences in the same area. When all the data are taken together, a contrast is evident between geo-petrographic and isotopic data on the one hand, and fluid-inclusion microthermometry on the other.

Mafic granulites of the Schirmacher region, East Antarctica: fluid inclusion and geothermobarometric studies focusing on the Proterozoic evolution of the crust

1997 ◽  
Vol 88 (1) ◽  
pp. 1-17 ◽  
Author(s):  
D. Rameshwar Rao ◽  
Rajesh Sharma ◽  
N. S. Gururajan
Keyword(s):  
Fluid Inclusion ◽  
Geothermal Gradient ◽  
East Antarctica ◽  
Compositional Zoning ◽  
T Box ◽  
History Of ◽  
Mineral Data ◽  
Temperature And Pressure ◽  
T Path ◽  
General Correspondence

AbstractIn the Proterozoic complex of the Schirmacher region of East Antarctica, a retrograde pressure–temperature (P–T) history has been inferred through quantitative geothermobarometry and fluid inclusion studies of the mafic granulites. Microthermometric investigations of the fluid phases trapped in quartz and garnet identified three types of inclusions, namely, earliest pure CO2 inclusions (0·987–1·057 g cm−3), CO2–H2O inclusions and aqueous inclusions.The temperature and pressure of metamorphism have been estimated through different calibrations of geothermometers and geobarometers. The mineral reactions and compositional zoning in the minerals record P–T conditions from nearly 837 ± 26°C, 7·1±0·2 kbar to 652 ± 33°C, 5·9 ± 0·3 kbar. A good correlation between the fluid and mineral data is observed. The isochores typical of highdensity CO2 fluids fall well within the P–T box estimated by mineral thermobarometry. The abundance of primary CO2 inclusions in early metamorphic minerals (notably quartz and primary garnet) and the general correspondence between fluid and mineral P–T data indicate a ‘fluid-present’ carbonic regime for the high-grade metamorpism; however, from the present data largescale CO2 advection could not be envisaged. The subsequent stages involved a decrease in CO2 density, a progressive influx of hydrous fluids and the generation of retrograde amphibolite facies metamorphism in the area.The estimated P–T conditions of the region suggest that the rocks were metamorphosed at a depth of 19–24 km, with a geothermal gradient of c. 3°5C km−1. The estimated P–T conditions of the rocks imply a clockwise P–T–t path with a gradual decrease in temperature of around 250°C and a decrease in pressure of around 1700 bar. They have a dP/dT gradient of ≈7 ± l bar °C−1, arguing for an isobaric cooling history of the terrane under normal thickened crust after the underplating of mantle-derived material.

The Variscan thermal history of west Clare, Ireland

1994 ◽  
Vol 131 (4) ◽  
pp. 545-558 ◽  
Author(s):  
E. Fitzgerald ◽  
M. Feely ◽  
J. D. Johnston ◽  
G. Clayton ◽  
L. J. Fitzgerald ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Fluid Migration ◽  
Burial History ◽  
Vertical Movements ◽  
Quartz Veins ◽  
History Of ◽  
Exploration Well ◽  
Reflectance Data

AbstractVitrinite reflectance data from Namurian rocks in west Clare suggest that high maturation levels, corresponding to palaeotemperatures of 340–370 °C, were attained prior to Variscan deformation. Fluid inclusions in syntectonic quartz veins homogenize between 330 °C and 50 °C with an accompanying decrease in salinity from 27 to 5 eq. wt % NaCl. Maximum fluid inclusion entrapment temperatures ranged from more than 300 °C to 250 °C during Variscan folding in County Clare. The observed maturation levels (c. 7.5% Rmax) far exceed values for simple burial maturation based on the estimated burial history and ‘normal’ geothermal gradients, and do not increase with depth in the Doonbeg No. 1 exploration well. Fluid advective heating is suggested as the most likely mechanism consistent with the Clare reflectance and thermometric data. Vein and shear zone dimensions preclude rapid vertical movements of hot fluids through the section, and extensive lateral fluid migration from sedimentary basins undergoing tectonically driven dewatering to the south or west is therefore proposed.

Calculation of organic maturation levels for offshore eastern Canada—implications for general application of Lopatin's method

1984 ◽  
Vol 21 (4) ◽  
pp. 477-488 ◽  
Author(s):  
D. R. Issler
Keyword(s):  
Heat Flow ◽  
Correlation Coefficient ◽  
Drilling Fluid ◽  
Vitrinite Reflectance ◽  
Geothermal Gradient ◽  
Scotian Shelf ◽  
Geothermal Gradients ◽  
Temperature Conditions ◽  
Bottom Hole ◽  
Correction Technique

Recorded maximum bottom-hole temperatures may vary significantly from true formation temperatures because of the effects of drilling fluid circulation. A theoretical temperature correction technique was applied to log-heading data to compute 191 static temperatures for 64 wells on the Scotian Shelf. A linear regression, performed on 140 computed temperatures, produced an average geothermal gradient of 2.66 °C/100 m; correlation coefficient 0.97. A geothermal gradient map constructed from the corrected data shows that areas of thicker sediment accumulation are marked by high geothermal gradients (e.g., Abenaki, Sable subbasins), whereas areas of shallow basement coincide with low gradients (e.g., LaHave Platform, Canso Ridge).It is proposed that the major control on the distribution of Scotian Shelf geothermal gradients is the thermal conductivity of the sediments. Radiogenic heat production within the sediments and subsurface fluid movement probably contribute to a lesser extent. Within the basins, higher heat flow due to thick salt accumulations at depth and the overall low conductivity of sediments above the salt lead to higher geothermal gradients. Low geothermal gradients in shallow basement areas are caused by the lack of salt and the relatively high conductivity of overlying sediments.A technique for calculating maturation levels of organic matter based on Lopatin's method and corrected bottom-hole temperatures was developed for the Scotian Shelf. A geologic model is constructed by considering the burial history of sediment for time invariant heat flow. From this, TTI (time–temperature index) values are derived to give the maturity level for specific sedimentary horizons. A comparison of 106 calculated TTI values with vitrinite reflectance measurements for 15 wells established a calibration of this technique for the Scotian Shelf. A correlation coefficient of 0.95 was obtained for the relation log TTI = 6.1841 log R0 + 2.6557.Maps showing the depth to calculated vitrinite reflectance values of 0.60 and 0.70% were constructed for the Scotian Shelf. It appears that burial rate, in addition to temperature, controls the location of various maturation levels. As one moves seaward, younger sediments increase in maturity and the oil window thickens. At equivalent depths, sediments at the basin margins are more mature than those farther seaward in the deeper parts of the basin. Sediments of the Canso Ridge area and over much of the LaHave Platform, excluding local downfaulted basins, have not attained sufficient maturity to have generated significant quantities of oil.TTI calibrations were established for the Labrador Shelf, the Grand Banks of Newfoundland, and the Canning Basin of Western Australia as above. Results indicate that tectonic history plays an important role in the calibration and that the slope of calibration lines may represent the departure from true time–temperature conditions in the modeling. Changes in heat flow with time lead to incorrect estimates of maturity when present-day geothermal gradients are used to approximate past temperature conditions. Also, uncertainties in the amount of erosion produce error in maturity estimates. The Scotian Shelf TTI calibration may be applicable to much of offshore eastern North America and parts of offshore western Europe and Africa.

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