Insights from fluid inclusions, thermal and PVT modeling for paleo-burial and thermal reconstruction of the Cordoba petroleum system (NE Mexico)

Carbonate reservoirs in the Cordoba petroleum system (NE Mexico) passed through a multiphase deformation history complicating the petroleum geology. The area evolved from passive margin and foreland setting to Laramide fold and thrust belt (FTB) that was subsequently buried below the Tertiary– Quaternary Veracruz Basin, which in turn underwent transpressional deformation. Reconstruction of paleo-burial (erosion) and paleo-thermicity through the different zones of the FTB and adjacent foreland is a challenging task since classical calibration tools fail to discriminate between several kinematic and thermal models. In this study results from detailed diagenetic and fluid inclusion (FI) analyses on carbonates from the western part of the Cordoba Platform helped constraining paleo-thermicity. Combined microthermometry, synchrotron FTIR analyses and PVT modeling of cogenetic hydrocarbonaqueous FI allowed also calculation of absolute pressures. Thermal modeling exercises calibrated with organic maturity parameters, bottom-hole temperatures or temperatures from FI demonstrate that without controlling also paleo-erosion the model results may be misleading.status: publishe

Metamorphism in the Stavelot Massif: a study of quartz veins in the basal Devonian conglomerates (Lochkovian)

The Stavelot-Venn Massif is the exposed Lower Palaeozoic inlier in the allochthonous Variscan Ardenne nappe in Belgium. This massif underwent two main orogenic phases, i.e. the Caledonian deformation phase and the Late Westphalian Variscan orogeny. The southern part of the Stavelot-Venn Massif is characterized by a greenschist-facies metamorphism, while a lower-graded Caledonian metamorphism may be totally overprinted. In the northern part illite crystallinity data indicate an anchizonal Caledonian metamorphism which is not influenced by a subsequent Variscan metamorphic phase. The Lower Devonian basal conglomerates, which overlay the Lower Palaeozoic of the Stavelot-Venn Massif, contain Caledonian and Variscan quartz veins. Fluid inclusions in these veins have been investigated to constrain the pressure and temperature conditions of the Caledonian and Variscan metamorphism. In the northern part of the Stavelot-Venn Massif, inclusions consist of two-phase, low salinity H2O-NaCl fluids and have homogenisation temperatures between 150°C and 200°C. Combined with a geothermal gradient of 50°C/km, a temperature and pressure range of respectively 180°C-280°C and 80-130MPa can be deduced. These values are comparable with those constrained by illite crystallinity. In the southern part of the Stavelot-Venn Massif, Caledonian quartz fragments are characterized by coexisting H2O-NaCl and H2O-CO2-NaCl fluids. Calculated trapping conditions vary between 280°C and 380°C with pressures between 80MPa and 300MPa. Furthermore the precipitation temperature of chlorites in the quartz veins and in the matrix of the conglomerates in the northern part of the Massif has been calculated. The temperature of 310°C is higher than the temperature of the surrounding host-rock during the Variscan (200°C based on the conodont colour alteration index and the vitrinite reflectance data). This could be due to the migration of warm fluids from the southern part of the Stavelot-Venn Massif towards the north during the Variscan orogeny.status: publishe

Visualizing pore scale alterations in artificial materials by CO2 exposure using HRXCT

Sequestration of CO2 in geological reservoirs is a transitional solution to reduce the concentration of greenhouse gases in the atmosphere, pending sufficient renewable energy alternatives. Carbonation at the earth’s surface can also be used to sequestrate CO2 in industrial processes, to stabilize mineral waste or even to transform waste into new innovative building materials. A thorough understanding of the mineral-CO2 interactions is therefore essential in the advances of industrial carbonation processes and the upscaling of geological storage. Due to the complexity and heterogeneity of reservoir rocks and minerals waste materials used in laboratory experiments, it is often a challenge to compile a model for reactive transport from physico-chemical data, deducted from reactor experiments, and even more difficult to calibrate or validate this model. This research aims to unravel the processes that occur when a CO2-enriched fluid reacts with different mineral phases in porous media and to quantify the influence of physico-chemical changes on the porosity and permeability of the rock. In order to deduct the influence of different parameters like mineralogy, reactive surface, porosity and permeability as unambiguously as possible, homogeneous artificial porous materials are used. These artificial materials are created from chemically pure mineral powders, with controllable petrophysical parameters (porosity, permeability, reactive surface, composition) and exposed to CO2-enriched fluid in batch and flow through reactors. The physico-chemical changes in the material are analysed using traditional methods and High Resolution X-ray Computed Tomography (HRXCT). HRXCT is a non-destructive technique that allows a complete characterization of the artificial rocks in 3D up to sub-micron resolution (400 nm). The non-destructive nature of this technique allows quantifying the changes (dissolution/precipitation) through time. By combining experimental results from traditional methods and the 3D HRXCT images with the models for reactive transport through porous media, the models can be validated and eventually calibrated. This will help also to better understand more complex experiments on complex reservoir materials and to optimize of the carbonation processes for the stabilisation of mineral waste and the production of innovative building materials

The use of palaeo-thermo-barometers and coupled thermal, fluid flow and pore-fluid pressure modelling for hydrocarbon and reservoir prediction in fold and thrust belts

Basin modelling tools are now more efficient to reconstruct palinspastic structural cross sections and compute the history of temperature, pore-fluid pressure and fluid flow circulations in complex structural settings. In many cases and especially in areas where limited erosion occurred, the use of well logs, bottom hole temperatures (BHT) and palaeo-thermometers such as vitrinite reflectance (Ro) and Rock-Eval (Tmax) data is usually sufficient to calibrate the heat flow and geothermal gradients across a section. However, in the foothills domains erosion is a dominant process, challenging the reconstruction of reservoir rocks palaeo-burial and the corresponding calibration of their past thermal evolution. Often it is not possible to derive a single solution for palaeo-burial and palaeo-thermal gradient estimates in the foothills, if based solely on maturity ranks of the organic matter. Alternative methods are then required to narrow down the error bars in palaeo-burial estimates, and to secure more realistic predictions of hydrocarbon generation. Apatite fission tracks (AFT) can provide access to time–temperature paths and absolute ages for the crossing of the 120 °C isotherm and timing of the unroofing. Hydrocarbon-bearing fluid inclusions, when developing contemporaneously with aqueous inclusions, can provide a direct access to the pore-fluid temperature and pressure of cemented fractures or reservoir at the time of cementation and hydrocarbon trapping, on line with the tectonic evolution. Further attempts are also currently made to use calcite twins for constraining reservoir burial and palaeo-stress conditions during the main deformational episodes. Ultimately, the use of magnetic properties and petrographical measurements can also document the impact of tectonic stresses during the evolution of the layer parallel shortening (LPS). The methodology integrating these complementary constraints will be illustrated using reference case studies from Albania, sub-Andean basins in Colombia and Venezuela, segments of the North American Cordillera in Mexico and in the Canadian Rockies, as well as from the Middle East.status: publishe

Developing tools for a better incorporation of geoscientific knowledge in policy making for a densely populated region

The need for a more efficient use of the subsurface in tackling a variety of issues is becoming more apparent, certainly in densely populated regions. For a better incorporation of geological knowledge into policy making, e.g., related to underground space use, raw materials management and (deep) subsurface planning for technologies such as geothermal energy, it is essential to develop user-friendly tools. These can translate geological information to field applications, which can be understood by policy officers, engineers, architects, etc. In Flanders (Belgium), such tools are developed and published on an open platform. Even though many tools are already available based on extensive 3D geological models, advances can still be made towards voxel models and 2D maps combining information for specific purposes