Figure 7 - uploaded by Johannes Schoenherr
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Transmitted light micrographs of halite from well A. a) Thin section scan of sample A4 shows halite with brownish solid bitumen at grain boundaries. Note the NE-SW trending strong grain shape-preferred orientation. Inset focuses at a grain showing an intragranular microcrack and grain boundaries, which are impregnated by solid bitumen. b) Overview micrograph of gamma-irradiated sample A11, showing grains with white polygonal subgrains, which are partly replaced by subgrain-free grains. Grain boundaries appear as dark lines. c Detail view at a lobate-shaped grain boundary (at the centre), which is bulged into the subgrain-rich grain. Note the elongated subgrains in the recrystallized part. The black elongated particle at centre left is solid bitumen.
Source publication
Die vorliegende Arbeit handelt über diagenetische und strukturelle Prozesse im Kohlenwasserstoffsystem der Spät-Präkambrisch bis Früh-Kambrischen Ara Gruppe im Südlichen Oman Salz Becken (SOSB) und Ghaba Salz Becken (GSB). Die Ara Gruppe wird von bis zu 150 m mächtigen Karbonat-Körpern (sog. stringer) aufgebaut, die z.T. hohe Fluid-Überdrücke auf...
Citations
... Debido a los altos rangos termales, estos pirobitúmenes tienen una huella geoquímica clara tales como bajos valores de HI (usualmente menos de 80 mg HC/ g TOC), un muy alto TMAX (>460°C) y una reducción de biomarcadores policíclicos (Schoenherr, 2007). Asimismo Wavrek et al, 1999 lo define como la alteración termal de hidrocarburo liquido preexistente para formar hidrocarburo sólido y gas asociado. ...
... Este último proceso decrece el peso molecular promedio del petróleo debido a la inyección de gas en la columna de petróleo, permitiendo la formación de petróleo liviano y precipitación de asfaltenos. La composición de los hidrocarburos sólidos desasfaltados representa una mezcla de NSO's, aromáticos y asfaltenos (Schoenherr, 2007). El proceso de desasfaltacion puede ser impulsado por el aumento en la profundidad de enterramiento del crudo hasta el punto en que el craqueo termal ocurra (Wavrek et al, 1999). ...
... Al mismo tiempo la biodegradación deja un enriquecimiento en los componentes NSO dentro de las formaciones, lo que conduce al incremento en la viscosidad del crudo. Este proceso de alteración microbial resulta en un decrecimiento de la gravedad API del petróleo atrapado, formando crudos pesados (Schoenherr, 2007 Otro proceso que se da en rangos de temperatura de 100-140°C y en algunas casos entre 160-180°C, señala que los hidrocarburos sólidos pueden ser formados como un subproducto de una reducción termoquímica de sulfato, que es la reacción entre sulfato acuoso (de disolución de anhidrita) y fluidos del petróleo para producir H2S calcita y un residuo sólido. Un caso excepcional que se da en ambientes de alta presión sucede cuando los H.S se maduran pero retienen sus propiedades químicas, esto quiere decir que sus características estructurales-moleculares y ópticas indican una variedad de muy alto rango mientras que su quimismo refleja patrones de una variedad de bajo rango; demostrándose así que la temperatura y la presión pueden tener efectos similares sobre la madurez de estos materiales (Gao et al, 2001). ...
Solid hydrocarbons are often associated with petroleum systems and can be found in source rocks, migration pathways, reservoirs and seals. However, the origin of the different types and their properties are still poorly understood. On the other hand, these materials can have negative effects in the reservoirs, reducing the quality of their properties (e.g. permeability, porosity) or even causing issues while drilling; but they can also be used as fuels and in a many of Industrial processes. In Colombia, the research on S.H (Solid Hydrocarbon) is just starting and is trying to contribute primarily to the characterization and the knowledge of the properties of this materials, along with comprehending their origin in a tectonic setting related to the evolution of the Colombian basins.
This research shows the characterization and probable origin of the S.H located in the MMV (Middle Magdalena Valley) and the E.C (Eastern Cordillera), where using different spectroscopic and geochemical techniques (NMR13C, Raman, FTIR-ATR, XRD, XRF SEM, Rock Eval Pyrolysis, Proximate and Elemental Analysis) thermal maturity and genetic relationships of the S.H according to the geological evolution of the basins were assessed. Moreover two main types were identified: Cata-impsonite and asphaltite in the south and north zones respectively. Finally, some implications as a paleotermometer were mentioned.
The Transylvanian basin is one of the major Tertiary sedimentary basins in the Carpathian-Pannonian region. Its thick sedimentary fill contains prominent Middle Miocene age salt that forms major diapir structures at the basin margins. The microstructural characteristics of the rock salt represent one of the main factors that determines the potential of a salt body for storage of hydrogen. The main aim of this study is to extend our understanding of the deformation mechanism of Praid rock salt located at the eastern margin of the Transylvanian basin. Based on petrography, we identified two types of rock salt: (1) layered salt with rather uniform grain size distribution showing alternation of greyish (clay mineral bearing) and white (clear halite) layers, and (2) massive grey salt with large, elongated halite crystals, accompanied by sub-micrometer size grains of halite. To shed light on the microstructure of the rock salt, we performed electron backscatter diffraction (EBSD) mapping, and studied gamma-irradiated samples both in the massive and layered salt samples. Dislocation creep and pressure solution creep were identified which acted concurrently in the Praid rock salt. The total strain rate falls between 1.2 and 1.3×10 ⁻¹⁰ s ⁻¹ . The results of this study reveal a complex deformation history of the salt body where coexisting and migrating fluids have played an important role. The outcome of this project contributes to the hydrogen storage potential assessment for the Transylvanian salt and to a better understanding of the structural evolution of the Transylvanian basin.
There has been a string of exploration discoveries in Cambrian Ara Group intra-salt carbonate reservoirs in the South Oman. Some of the reservoirs failed to produce at expected rates due to halite presence in the pore space, which is one of the highest risks for hydrocarbon exploration in this area. The objective of this study was to define novel quantitative algorithm to estimate halite volumes in the pore space.
Although halite cementation is known as a major risk for hydrocarbon production, a limited number of studies have focused on the impact of halite cementation on productivity, well integrity and ultimate recovery. The quantitative halite volume evaluation based on the logging data required an integrated approach to open hole and cased hole data collection and analysis. The open hole data included: thin section and XRD core analysis, density, neutron, sonic, resistivity, formation pressure and sigma capture-cross section. Net pay cut-off based on calculated halite volume was defined. Cased hole production logging was used to confirm net cut-off definition. The integrated logging data analysis and the developed quantitative halite volume evaluation algorithm mainly based on sigma log was successfully implemented in a few ongoing development projects. The evaluation results were successfully used for hydrocarbon volume calculations, well placement and perforation interval selection to improve production performance and reduce field development uncertainty in recoverable volumes. Understanding of consistent pattern for halite distribution allow improve exploration success. Avoiding perforation of intervals with high halite content in the pore space reduced production deferment due to surface equipment and tubing plugging by salt. Appreciation for the role of halite plugging in the reservoirs properties distribution and deterioration significantly improve history match for hydrodynamic models. The evaluation algorithm for quantitative halite volume estimation in the pore space have been developed and introduced for the first time and benefits from its implementation are expected for the upcoming exploration and development projects for the salt encased carbonate reservoirs.
Organic matter occurring in the form of macerals and natural solid bitumens in peats, coals, and siliciclastic sediments of various stratigraphic ages and locations was studied by means of conventional incident light microscopy and CLSM. Classical optical microscopic investigations are restricted by conventional 2-D imaging and are often hindered by the associated out-of-focus-blur effects. The qualitative application of CLSM overcomes these limitations, permitting to reveal precisely 3-D morphology and detailed microstructure of autofluorescent organic matter. The in depth examinations along Z-axis in XY, XZ, or YZ scanning modes at increments of 250 nm are capable to reconstruct 3-D internal configuration and arrangement occurring in autofluorescent macerals. The non-invasive and non-destructive laser-raster technique is applied to characterize in situ autofluorescent organic particles at micron to sub-micron scale resolution in polished whole rock pellets. In this study, we demonstrate that CLSM is suitable to (i) detect fine-scale microstructure of autofluorescent organic matter, (iii) reconstruct 3-D morphology at cellular and tissue level, (iii) analyze maceral composition in terms of its relicts and fragments beyond the classical optical assignment limits, (iv) detect and examine inorganic components enclosed in the embedding mineral-bituminous groundmass, and (v) differentiate mineral constituents from the remaining organic matter.
The Northern Calcareous Alps are part of the Eastern Alps in Austria and Germany. The Mesozoic units of this fold-and-thrust belt were detached, thrusted and stacked along the evaporitic Haselgebirge Formation. Exposed in salt mines, rocksalt and mudrock form a two component tectonite: The rock type “haselgebirge” consists of 10–70 wt % halite with silt- to gravel- or block-sized components within a halite matrix, and the “kerngebirge” with >70 wt % halite. All rock types studied are fault rocks. By use of a temperature-independent subgrain size piezometer, the paleo-differential stress of halite was calculated at ca. 2.5 MPa in Altaussee and ca. 4.5 MPa in Berchtesgaden. Including data from a grain-size piezometer, temperatures were estimated at ca. 150±20°C and 110±10°C. This implies very high strain rates, which are about 10−10 to 10−9 s−1. During the tectonic movement, the halite deformed, recrystallized, and crystallized as veins in mudrock fractures. We interpret high overpressure of the pore fluid to have significantly contributed to fracturing of the mudrock.
