Ricardo Ruiz-Monroy

• This dissertation was carried out as part of the international and interdisciplinary graduate school StRATEGy. This group has set itself the goal of investigating geological processes that take place on different temporal and spatial scales and have shaped the southern central Andes. This study focuses on claystones and carbonates of the Yacoraite Fm. that were deposited between Maastricht and Dan in the Cretaceous Salta Rift Basin. The former rift basin is located in northwest Argentina and is divided into the sub-basins Tres Cruces, Metán-Alemanía and Lomas de Olmedo. The overall motivation for this study was to gain new knowledge about the evolution of marine and lacustrine conditions during the Yacoraite Fm. Deposit in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects that were examined within the scope of this dissertation are the conversion of organic matter from Yacoraite Fm. into oil and its genetic relationship to selected oils produced and natural oil spills. The results of my study show that theThis dissertation was carried out as part of the international and interdisciplinary graduate school StRATEGy. This group has set itself the goal of investigating geological processes that take place on different temporal and spatial scales and have shaped the southern central Andes. This study focuses on claystones and carbonates of the Yacoraite Fm. that were deposited between Maastricht and Dan in the Cretaceous Salta Rift Basin. The former rift basin is located in northwest Argentina and is divided into the sub-basins Tres Cruces, Metán-Alemanía and Lomas de Olmedo. The overall motivation for this study was to gain new knowledge about the evolution of marine and lacustrine conditions during the Yacoraite Fm. Deposit in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects that were examined within the scope of this dissertation are the conversion of organic matter from Yacoraite Fm. into oil and its genetic relationship to selected oils produced and natural oil spills. The results of my study show that the Yacoraite Fm. began to be deposited under marine conditions and that a lacustrine environment developed by the end of the deposition in the Tres Cruces and Metán-Alemanía Basins. In general, the kerogen of Yacoraite Fm. consists mainly of the kerogen types II, III and II / III mixtures. Kerogen type III is mainly found in samples from the Yacoraite Fm., whose TOC values are low. Due to the adsorption of hydrocarbons on the mineral surfaces (mineral matrix effect), the content of type III kerogen with Rock-Eval pyrolysis in these samples could be overestimated. Investigations using organic petrography show that the organic particles of Yacoraite Fm. mainly consist of alginites and some vitrinite-like particles. The pyrolysis GC of the rock samples showed that the Yacoraite Fm. generates low-sulfur oils with a predominantly low-wax, paraffinic-naphthenic-aromatic composition and paraffinic wax-rich oils. Small proportions of paraffinic, low-wax oils and a gas condensate-generating facies are also predicted. Here, too, mineral matrix effects were taken into account, which can lead to a quantitative overestimation of the gas-forming character. The results of an additional 1D tank modeling carried out show that the beginning (10% TR) of the oil genesis took place between ≈10 Ma and ≈4 Ma. Most of the oil (from ≈50% to 65%) was generated prior to the development of structural traps formed during the Plio-Pleistocene Diaguita deformation phase. Only ≈10% of the total oil generated was formed and potentially trapped after the formation of structural traps. Important factors in the risk assessment of this petroleum system, which can determine the small amounts of generated and migrated oil, are the generally low TOC contents and the variable thickness of the Yacoraite Fm. Additional risks are associated with a low density of information about potentially existing reservoir structures and the quality of the overburden.…
• Diese Dissertation wurde im Rahmen des internationalen und interdisziplinären Graduiertenkollegs StRATEGy durchgeführt. Diese Gruppe hat sich zum Ziel gesetzt, geologische Prozesse zu untersuchen, die auf unterschiedlichen zeitlichen und räumlichen Skalen ablaufen und die südlichen Zentralanden geprägt haben. Diese Studie konzentriert sich auf die Tonsteine und Karbonate der Yacoraite Fm., die zwischen Maastricht und Dan im kreidezeitlichen Salta-Grabenbecken abgelagert wurden. Das ehemalige Riftbecken liegt im Nordwesten Argentiniens und gliedert sich in die Teilbecken Tres Cruces, Metán-Alemanía und Lomas de Olmedo. Die übergreifende Motivation für diese Studie war es, neue Erkenntnisse über die Entwicklung der marinen und lakustrinen Bedingungen während der Ablagerung der Yacoraite Fm. in den Tres Cruces und Metán-Alemanía Sub-Becken zu gewinnen. Weitere wichtige Aspekte, die im Rahmen dieser Dissertation untersucht wurden, sind die Umwandlung von organischer Materie der Yacoraite Fm. in Öl sowie deren genetische Beziehung zuDiese Dissertation wurde im Rahmen des internationalen und interdisziplinären Graduiertenkollegs StRATEGy durchgeführt. Diese Gruppe hat sich zum Ziel gesetzt, geologische Prozesse zu untersuchen, die auf unterschiedlichen zeitlichen und räumlichen Skalen ablaufen und die südlichen Zentralanden geprägt haben. Diese Studie konzentriert sich auf die Tonsteine und Karbonate der Yacoraite Fm., die zwischen Maastricht und Dan im kreidezeitlichen Salta-Grabenbecken abgelagert wurden. Das ehemalige Riftbecken liegt im Nordwesten Argentiniens und gliedert sich in die Teilbecken Tres Cruces, Metán-Alemanía und Lomas de Olmedo. Die übergreifende Motivation für diese Studie war es, neue Erkenntnisse über die Entwicklung der marinen und lakustrinen Bedingungen während der Ablagerung der Yacoraite Fm. in den Tres Cruces und Metán-Alemanía Sub-Becken zu gewinnen. Weitere wichtige Aspekte, die im Rahmen dieser Dissertation untersucht wurden, sind die Umwandlung von organischer Materie der Yacoraite Fm. in Öl sowie deren genetische Beziehung zu ausgewählten produzierten Ölen und natürlichen Ölaustritten. Die Ergebnisse meiner Studie zeigen, dass die Ablagerung der Yacoraite Fm. unter marinen Bedingungen begann und sich bis zum Ende der Ablagerung in den Tres Cruces- und Metán-Alemanía-Becken ein lakustrines Milieu entwickelte. Im Allgemeinen besteht das Kerogen der Yacoraite Fm. überwiegend aus den Kerogentypen II, III und II/III-Mischungen. Der Kerogentyp III findet sich vor allem in Proben aus der Yacoraite Fm., deren TOC-Werte niedrig sind. Aufgrund der Adsorption von Kohlenwasserstoffen an den Mineraloberflächen (Mineralmatrixeffekt) könnte der Gehalt an Typ-III-Kerogen mit der Rock-Eval-Pyrolyse in diesen Proben überschätzt werden. Untersuchungen mittels organischer Petrographie zeigen, dass die organischen Partikel der Yacoraite Fm. hauptsächlich aus Alginiten und einigen Vitrinit-artigen Partikeln bestehen. Die Pyrolyse-GC der Gesteinsproben zeigte, dass die Yacoraite Fm. schwefelarme Öle mit einer überwiegend Wachs-armen paraffinisch-naphthenisch-aromatischen Zusammensetzung und paraffinische Wachs-reiche Öle generiert. Geringe Anteile paraffinischer, Wachs-armer Öle und einer Gaskondensat-generierenden Fazies werden ebenfalls vorausgesagt. Auch hier wurden Mineralmatrixeffekte berücksichtigt, die zu einer quantitativen Überschätzung des gasbildenden Charakters führen können. Die Ergebnisse einer zusätzlich durchgeführten 1D-Beckenmodellierung zeigen, dass der Beginn (10 %TR) der Ölgenese zwischen ≈10 Ma und ≈4 Ma stattfand. Der größte Teil des Öls (von ≈50 % bis 65 %) wurde vor der Entwicklung struktureller Fallen gebildet, die während der plio-pleistozänen Diaguita Deformatiosphase gebildet wurden. Nur ≈10 % des insgesamt generierten Öls wurde nach der Entstehung struktureller Fallen gebildet und potentiell darin gefangen. Wichtige Faktoren in der Risikobewertung dieses Erdölsystems, welche die geringen Mengen an generiertem und migriertem Öl bestimmen können, stellen die allgemein niedrigen TOC-Gehalte und die variable Mächtigkeit der Yacoraite Fm. dar. Weitere Risiken sind mit einer niedrigen Informationsdichte über potentiell vorhandene Reservoirstrukturen und die Qualität der Deckgesteine verbunden.…
• This dissertation was carried out within the framework of the international and interdisciplinary research training group StRATEGy whose aim is to study geological processes occurring at different times and spatial scales that have shaped the southern Central Andes. The study focuses on the shales and carbonates of the Yacoraite Fm. deposited in the Salta rift basin (NW Argentina) during the Maastrichtian to Danian, and is divided into the Tres Cruces, Metán-Alemanía, and Lomas de Olmedo sub-basins. The Yacoraite Fm. is considered the potential source rock for most oil fields in NW Argentina. The overall motivation for this research was to provide new insights into the occurrence of marine and lacustrine settings during the deposition of the Yacoraite Fm. in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects assessed in this research are the likely transformation of organic matter of the Yacoraite Fm. into oil as well as its genetic relation to selected produced oils and natural oil seep samples. Fifty-twoThis dissertation was carried out within the framework of the international and interdisciplinary research training group StRATEGy whose aim is to study geological processes occurring at different times and spatial scales that have shaped the southern Central Andes. The study focuses on the shales and carbonates of the Yacoraite Fm. deposited in the Salta rift basin (NW Argentina) during the Maastrichtian to Danian, and is divided into the Tres Cruces, Metán-Alemanía, and Lomas de Olmedo sub-basins. The Yacoraite Fm. is considered the potential source rock for most oil fields in NW Argentina. The overall motivation for this research was to provide new insights into the occurrence of marine and lacustrine settings during the deposition of the Yacoraite Fm. in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects assessed in this research are the likely transformation of organic matter of the Yacoraite Fm. into oil as well as its genetic relation to selected produced oils and natural oil seep samples. Fifty-two outcropping samples from the Yacoraite Fm. collected in the Tres Cruces and Metán-Alemanía sub-basins, seven oil seep samples from the Tres Cruces and Lomas de Olmedo sub-basins and eight produced oils from the latter sub-basin were evaluated. Characterization of the depositional environment and kerogen types of the Yacoraite Fm. was performed using various geochemical analyses encompassing pyrolysis, chromatography, spectrometry and petrography. Minerals were analyzed by X-ray diffraction. The elemental composition of rock samples was determined by X-ray fluorescence and more precise quantification was done by ICP-MS analysis. The study of the hydrocarbon potential of the Yacoraite Fm. was addressed by the following analyses of its organic matter and modeling procedures: • The assessment of the amount, quality, and thermal maturity of the organic matter; • Measurement of the rate of thermal cracking (bulk kinetics) of the organic matter into oil; • The extrapolation of high heating rate kinetics to low heating rates at geological conditions using the first-order kinetic approach provided by the Arrhenius equation; • The prediction of the composition (compositional kinetics) and the phase behavior of its first-formed petroleum; • The specific activation energy distribution of the bulk kinetics of representative samples collected in the Tres Cruces sub-basin were used in the 1D-basin modeling, enabling a comparison between the timing of oil generation and the timing of the formation of structural traps. Subsequently, the implications of these variables on the accumulation of oil in the Tres Cruces sub-basin were assessed. The characterization of produced oils and oil seep samples was carried out by chromatographic and spectrometric techniques. Genetic relationships (source rock-oil correlation) of the oil seep samples in the Tres Cruces sub-basin was studied by comparing their compositional affinities to rock extracts from outcropping samples of the Yacoraite Fm. in the same sub-basin. Since no rock samples were available from the Lomas de Olmedo sub-basin, the source-rock correlation for the oil seep samples and the produced oils assume that the Yacoraite Fm. in this sub-basin has similar organofacies as in the Tres Cruces and Metán-Alemanía sub-basins. The results of this research indicate that the deposition of the Yacoraite Fm. began in marine environments. Lacustrine settings developed during the middle part and predominated towards the end of the deposition in the Tres Cruces and Metán-Alemanía sub-basins. In general, the kerogen of the Yacoraite Fm. is predominantly composed of Type II, II/III, and Type III kerogens. The latter is largely found in samples from the Yacoraite Fm. whose TOC values were low. In these samples, the content of Type III kerogen could be overestimated with Rock-Eval pyrolysis due to hydrocarbon adsorption on mineral surfaces (mineral-matrix effect). Organic petrography showed that the organic particles of the Yacoraite Fm. correspond mainly to alginites and some vitrinite-like particles. Pyrolysis-GC of whole-rock samples indicated that the Yacoraite Fm. generates low sulphur oils with a mainly Paraffinic-Naphthenic-Aromatic Low Wax composition and Paraffinic High Wax oils. Minor contributions of Paraffinic Low Wax Oil and Gas condensate-generating facies are also predicted. Mineral-matrix effects can lead to an overestimation of the gas-prone character and were considered. Extrapolation of bulk kinetics experiments to a geological heating rate of 3 K/Myr reveals that the oil generation from the Yacoraite Fm. in the Tres Cruces sub-basin occurs in a range of approximately 60 °C. The onset (10%TR) of oil generation occurs at geological temperatures from 108 °C to 132 °C. The complete transformation of the organic matter into oil (90%TR) is reached at temperatures between 142 °C and 169 °C. The gas exsolution from the oil occurs at pressures below 200 bar as predicted from PVT-compatible compositional kinetics with subsequent separation of two phases and the increase in liquid viscosity at depths <1.8 km. The analysis of outcrop samples of the Yacoraite Fm. collected in the Metán-Alemanía and Tres Cruces sub-basins document that their maturity is at least at the onset of oil generation. The formation is more mature in the deeper buried centers of the basins being in the main oil window, as indicated by the presence of genetically related oil seep samples and supported by predictions of thermal modeling. The results of 1D-basin modeling indicate that the onset (10%TR) of oil generation occurred between ≈10 Ma and ≈4 Ma. Most of the oil (from ≈50% to 65%) was generated before the structural traps associated with the Diaguita tectonic phase (c.a. 2.5 Ma) formed. The amount of oil generated after the formation of structural traps and potentially accumulated in them accounts for ≈10%. The petroleum system risk assessment identifies the generally low TOC content and variable thickness of Yacoraite Fm. as important factors that may determine the low volumes of generated and migrated oil. Additional risks are associated with the lack of information regarding the existence of reservoirs and the quality of the seals. Oil-source rock correlations based on depositional-, age- and maturity-related biomarkers show that the oil samples of the Caimancito oil field and from Well-10 of the Martinez del Tineo oil field were generated from the Yacoraite Fm., while partial correlations are determined between this formation and the oil samples from Well-18 and Chirete x100-1. The oil samples from well-11 and Río Pescado show no correlation and were sourced from a different rock. According to the project partners, it is most likely the Devonian Los Monos Fm. The oil-oil correlations reflect the source oil-source rock correlations mentioned above and were supported by the ratios of light hydrocarbons using the classical approach of Halpern (1995). The Río Pescado and well-11 oil samples lack most of the biomarkers, which distinguishes them from the rest of the oils. The sample from well-11 was found to be a mixture of oils of varying thermal maturity. The least mature oil in this mixture contains stigmastane and correlates with the oil sample from the Caimancito-21 well. The most mature sample is characterized by higher concentrations of diamantanes and adamantanes. An anomalously high uranium content was measured in one sample at the base of the Yacoraite Fm. in the west sector of the Metán-Alemanía sub-basin. High radiation doses appear to be the cause for the very low hydrocarbon generation during Rock-Eval pyrolysis. The sample is composed mainly of alginites with minor amounts of terrigenous material and plots in the field of Type IV kerogen in a pseudo-Van Krevelen diagram. Since radiation induces aromatization in the kerogen structure, it potentially mimics higher thermal maturity as determined by vitrinite reflectance. The higher Tmax is caused by the high adsorption of hydrocarbons on the highly-aromatized kerogen and the contribution of hydrocarbons adsorption on mineral surfaces. The lack of biomarkers in the solvent-extracted portion (bitumen) of the same highly-irradiated sample prevents the characterization of kerogen type and the depositional environment. However, unlike Py-GC results for kerogen, GC-FID analysis on extracted bitumen still shows n-alkanes, pristane, and phytane. This may not only indicate a different response of bitumen and kerogen to radiation, at least in the magnitude, but also offers an alternative for kerogen typing in samples where the kerogen is highly affected by radiation which makes its classification unreliable. In this example, the ratios of pristane/n-C17 and phytane/n-C18 in bitumen indicate that a Type II/III kerogen composes this sample, which is consistent with the presence of alginite as the main organic component and some vitrinite-like particles. In conclusion, molecular geochemical analyses have documented the presence of gammacerane in extracts of the Yacoraite Fm. which indicate the development of hypersaline conditions as well as the changing depositional environment of the Yacoraite Fm. from marine towards lacustrine settings. The variability of organofacies of this formation in the Tres Cruces and Metán-Alemanía sub-basins is a consequence of the changes in the depositional environment. Future work may provide insights into the evolution of paleosalinity during Yacoraite Fm. deposition by using specific proxies e.g., methyltrimethyltridecylchromans. Future research may include characterizing the NSO fraction of these oils as well as elucidating possible fractionation during expulsion, migration, and accumulation. A regional study is needed to clarify the uncertainties associated with the existence of the reservoir, the quality of the seals and to improve the data-input for thermal modeling for the Tres Cruces sub-basin. Studies that aim to increase the database of the concentration of methyldiamantanes (3- + 4-) and methyladamantanes (1- + 2-) in produced oils will provide a threshold for the assessment of oil cracking. Further research is aimed at helping to understand how the distribution of uranium can affect the different responses of bitumen and kerogen to radiation.…