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Petroleum migration pathways through a basin are determined by the three-dimensional distribution of discontinuous sealing surfaces, which are usually parallel to bedding. The petroleum migrates below the sealing surface taking the structurally most advantageous route. The three-dimensional distribution of migration pathways within the petroleum system can be modelled on a personal computer using a program based on the parameters developed during the research summarised in this thesis. Application of the model to the Paris, Williston, West of Shetlands and Wessex Basins demonstrates that a good correlation can be made between predicted pathways and discovered accumulations using simple models. Migration pathways form a dense network overlying hydrocarbon generating areas in the central parts of basins. Towards the basin margins they commonly become increasingly focused into discrete pathways by the sealing-surface morphologies. The Paris and Williston Basin research showed how relatively minor structuring of geological strata can result in a significant focusing of pathways. Eventually these pathways may reach the surface as shown by seepages. Research in the Wessex Basin revealed that reverse modelling of pathways from seeps assists in the prediction of the location of leaking accumulations. Deflection of the pathways from the structurally most advantageous route below the sealing surface may be caused by lateral sealing barriers due to facies variation in the carrier rock below the seal, fault juxtaposition, or cross-formational seals such as salt intrusions. Deflection of pathways also occurs where there are hydrodynamic conditions in response to topography-driven groundwater flow.

Carbonate reservoirs hold more than 50 % of Earth’s remaining conventional hydrocarbon. However, recovery from these reservoirs is notoriously difficult due to the complex and multiple scales of porosity. This heterogeneity is a function of both the depositional environment and of subsequent diagenetic processes. This thesis examines the processes that have controlled the reservoir quality of three Early Cretaceous carbonate oil fields (A, B, and C), in particular the role of deposition, diagenesis and the timing of oil charge in controlling final properties. Results are then used to help provide a theoretical basis for the modelling and prediction of reservoir quality and to improve the calibration of basin models. Field A and B are stacked and highly compartmentalised giant oil fields in the U.A.E. that are dominated by muddy fabrics and have a highly variable porosity (0- 35 %) and permeability (0.01-830 mD). Although the depositional environment strongly determines the location of reservoirs extensive diagenesis, through cementation and dissolution, has greatly modified the porosity and permeability of the reservoirs. Bulk δ13C values obtained from the main pore occluding calcite and dolomite cements are similar to the δ13C values of bulk micrite for the reservoir interval in which they are now present. This suggests that the cements that are occluding the pore space in each stacked reservoir are locally sourced and implies that each reservoir behaves as a relatively closed system during cement precipitation. In-situ (SIMS) δ18OVPDB values were obtained for the complete calcite cementation history of multiple reservoirs in Field A and B. The δ18OVPDB values for the first (oldest) calcite cement zone in each reservoir can be related to the global δ18OVPDB marine curve during the Hauterivian-Aptian and to million-year scale major climatic cooling events. The δ18OVPDB values for successive cement zones then progressively decrease, which is related to successive precipitation as a result of increasing temperature during burial in a relatively closed system. In-situ (SIMS) δ18OVPDB data together with oil inclusion occurrence suggest that initial oil charge (from the Dukhan Formation), at ~ 55-45 Million years ago (Mya) in Field A, reduced the cementation rate in the oil reservoir and preserved porosity. Whereas in the coeval aquifer a large volume of cement precipitated, after oil entered the oil reservoir, that greatly reduced porosity. Furthermore, the most reduced δ18OVPDB and mMg/mCa values are obtained from the cements in the shallowest (youngest) reservoirs, suggesting that cementation ceased in the deepest reservoirs first. This can be related to hydrocarbon stopping cementation or to the complete occlusion of effective porosity in the older reservoirs prior to the younger. After calcite and dolomite cementation ceased in the reservoirs of Field A and B a large scale dissolution event has been identified which significantly enhanced porosity. This dissolution event is then followed by the precipitation of authigenic kaolinite. Basin modelling reveals that this dissolution event is likely to be related to the thermal maturation of sedimentary organic matter that is present within local intraformational seals and to the migration of organic acids prior to a second hydrocarbon charging event (at ~ 45 Mya). The aluminium, that is required for the formation of kaolinite, would then have been brought into the system by complexing with the organic compounds derived from this maturation event. Field C is an oil field located in offshore Brazil. The field is dominated by high energy facies that have porosities which range from 5 % to 39 %, and permeabilities from 0.1 mD to 8.1 D. The depositional poro-perm properties of the oil reservoir have undergone little diagenetic alteration; however, the aquifer is extensively cemented and the porosity is much reduced. All the cements identified, by both petrography and stable isotopic analyses, in the oil reservoir are early and are thought to have formed from a pore fluid similar to, or slightly evolved from, Early Cretaceous seawater. Basin modelling suggests that oil may have entered the field slightly after deposition (at ~105 Mya) and led to the preservation of high porosities and permeabilities in the oil reservoir by stopping cementation.

This study presents an integrated evaluation of the burial and thermal history of an exhumed (uplifted and eroded) basin, and investigates the implications for the evolution of reservoir quality of the Ordovician sandstone in the Illizi Basin, Algeria. Complementary techniques including sonic compaction analysis, apatite fission track analysis, thermal maturity analysis, fluid inclusion microthermometry, and sandstone petrography are integrated to provide calibration for burial and thermal history models and diagenetic forward modelling, in order to predict variations in sandstone reservoir quality across the study area. The Illizi Basin has been structurally modified due to multiple exhumation events, including the uplift of the Hoggar Massif, which resulted in exhumation of the flanking sedimentary basins over a distance of 1,500 km from north to south. This study presents new apatite fission track data and analyses that constrain the onset of major exhumation in the Illizi Basin to the Eocene with exhumation magnitudes estimated to be 1-1.4 km in the study area. The study area contains a multi trillion cubic foot gas-condensate accumulation within a large four way dip closure. Hydrocarbon generation occurred during two main phases in the Carboniferous and the Mesozoic, but ceased during Cenozoic exhumation. Due to the Cenozoic tilting of the Illizi Basin in response to the uplift of the Hoggar Massif to the south, the present-day structural trap is interpreted to have formed after the main hydrocarbon generation phases. Therefore, alternative charging mechanisms of this post-peak burial trap are required and explored. In addition, new fluid inclusion data provides evidence of a significant fluid flow event within the Illizi basin, triggered by Cenozoic exhumation. Brines hosted present-day in the Ordovician sandstone in the study area are shown to be genetically linked to Triassic-Liassic evaporites deposited over 400 km to the north. Overpressure dissipation during exhumation is proposed to be a potential driving mechanism for the late stage remobilization of deep brines. A major pre-drill risk in many North African Paleozoic plays relates to sandstone reservoir quality, largely due to extensive quartz diagenesis. The Ordovician reservoir in the study area is characterised through petrography and core analysis, and the impact of burial and thermal history on the reservoir quality is investigated through diagenetic forward modelling. Results indicate that facies and variations in thermal history are a major control on preserving reservoir quality. This study demonstrates the importance of integrating the burial and thermal history, depositional facies and diagenetic history during predictive reservoir quality studies, particularly in exhumed basins where the burial and exhumation history may be complex, and present-day depth or geometry is not indicative of the past. Methodologies and implications from this study could be applied to exhumed basins in general.

Saline aquifers and depleted hydrocarbon fields situated beneath the North Sea are currently being proposed as storage repositories for anthropogenic CO2 captured from point source emitters in the UK and mainland Europe. Two experimental sites are already operating successfully offshore Norway: Sleipner since 1996 and Snøhvit since 2007, collectively storing several million tonnes of CO2/year in the sub-surface. Despite the apparent success of these current projects, one of the major public and scientific concerns is the ability of storage sites to retain CO2 on the millennial timescales required for CO2 plume stabilisation and dissolution. Some areas of the North Sea are also known to contain palaeo-gas seepage pathways within overburden sediments that overlie deeper hydrocarbon reservoirs (e.g. Witch Ground Graben). These areas either need to be avoided for CO2 storage or rigorously assessed in terms of leakage risk. Since the Sleipner storage site lies within such a province, this thesis delivers a detailed evaluation of the Nordland Group overburden and a critical assessment of its long-term sealing capability for CO2. From interpretation and detailed mapping of a baseline 3D seismic dataset (acquired before CO2 injection operations commenced in 1996), we have identified numerous palaeo-migration pathways and high-amplitude seismic anomalies within the Nordland Group overburden sediments deposited above the Sleipner CO2 storage site. We attributed these features to thermogenic or biogenic gas migration, accumulation and bio-degradation over geological time. We also mapped a complex network of sand-filled, glacial channels and tunnel valleys distributed within a few hundred metres below seabed and highlighted their significance as potential fluid migration networks and/or secondary storage containment for leaking CO2. Of further significance, we confirmed that these overburden features also create spatial density variations that impact on the accuracy of seismic time-depth conversions, resulting in the probability of topographic distortions being propagated into seismic interpretations and models. To the best of our knowledge no such detailed mapping of the Nordland Group overburden at Sleipner has been undertaken previously. To determine whether the top layer of the CO2 plume at Sleipner might encounter these relict pathways as it ascends and migrates laterally beneath the caprock, we evaluated the critical column heights required for a CO2 accumulation to enter such a pathway under a range of storage conditions for a CH4/CO2/brine system; assuming that these pathways currently contain methane gas. Risking scenarios were based on a range of phase saturation, pressure, temperature, density, viscosity, interfacial tension and wettability conditions likely to be encountered at depths commensurate with the caprock at Sleipner. We concluded that given certain conditions at the caprock, CO2 could leak more easily into palaeo-migration pathways than CH4 (i.e. at lower entry pressures and therefore smaller column heights), assuming that brine densities and, most importantly, pore radii have not changed significantly over geological time (i.e. no cementation or dissolution has taken place). To further understand the dynamic significance of these palaeo-migration pathways, channels and tunnel valleys, including their ability to form inter-connected leakage/migration networks, we constructed a series of high-resolution 3D models of the Sleipner storage site and overburden, then used stochastic basin modelling and simulation techniques to investigate the processes involved during the introduction of CO2 into the storage site over a prolonged time period. Models were populated with geological, stratigraphic and structural information derived from our seismic interpretation. Flow simulations were calibrated to published data and matched to the present-day plume distribution. The absence of observational reservoir pressure and temperature data from Sleipner introduces significant uncertainty to model outcomes with respect to CO2 density and column height estimates and to surmount this difficulty we constrained the caprock temperature to CO2 density estimates obtained from the most recent gravity data observations at Sleipner. We concluded that the overburden heterogeneity is significant and palaeo-migration pathways, highpermeability channels and tunnel valleys at Sleipner may become potential migration pathways for CO2 as the plume continues to spread laterally over the coming decade, but the possible storage response is difficult to quantify given the absence of sufficient overburden rock property information and accurate pressure and temperature data for the storage site. The overall conclusion from this work is that insufficient information was collected within the Sleipner area prior to storage site development and too many significant studies which should have been performed as a pre-requisite (e.g. obtaining a caprock sample for laboratory testing of potential seal capacity), were actually performed some years after CO2 injection operations had already commenced. The pressure and temperature conditions at the caprock depth for the Sleipner storage site are also marginal in terms of maintaining CO2 above critical point conditions in dense phase and thus maximising storage efficiency. Most significantly, no rigorous overburden mapping and risking was performed for Sleipner (such as the work described in this thesis), thus the fact that no leakage has been detected at Sleipner is more due to good fortune than following best practices. Hopefully, our work has highlighted these key deficiencies so that future CO2 storage site feasibility and development studies will be performed more diligently.

[EN] Adaptation to the multiple facets of global change challenges the conventional means of sustainably planning and managing water resources at the river basin scale. Numerous demand or supply management options are available, from which adaptation measures need to be selected in a context of high uncertainty of future conditions. Given the interdependency of water users, agreements need to be found at the local level to implement the most effective adaptation measures. Therefore, this thesis develops an approach combining economics and water resources engineering to select a cost-effective programme of adaptation measures in the context of climate change uncertainty, and to define an equitable allocation of the cost of the adaptation plan between the stakeholders involved. A framework is developed to integrate inputs from the two main approaches commonly used to plan for adaptation. The first, referred to as "top-down", consists of a modelling chain going from global greenhouse gases emission scenarios to local hydrological models used to assess the impact of climate change on water resources. Conversely, the second approach, called "bottom-up", starts from assessing vulnerability at the local level to then identify adaptation measures used to face an uncertain future. Outcomes from these two approaches are integrated to select a cost-effective combination of adaptation measures through a least-cost optimization model developed at the river basin scale. The model is then used to investigate the trade-offs between different planning objectives defined in terms of environmental flow requirements, irrigated agriculture development, and the cost of the programme of measures. The performances of a programme of measures are finally assessed under different climate projections to identify robust and least-regret adaptation measures. The issue of allocating the cost of the adaptation plan is considered through two complementary perspectives. The outcome of a negotiation process between the stakeholders is modelled through the implementation of cooperative game theory to define cost allocation scenarios. These results are compared with cost allocation rules based on social justice principles to provide contrasted insights into a negotiation process. This innovative framework has been applied in a Mediterranean case study in the Orb River basin (France). Mid-term climate projections, downscaled from 9 General Climate Models, are used to assess the uncertainty associated with climate projections. Demand evolution scenarios have been developed to project agricultural and urban water demands on the 2030 time horizon. The least-cost river basin optimization model developed in GAMS allows the cost-effective selection of a programme of measures from a catalogue of 462 supply and demand management measures. Nine cost allocation scenarios based on different social justice principles have been discussed through face-to-face semi-structured interviews with 15 key informants and compared with solution concepts from cooperative game theory for a 3-player game defined at the river basin scale. The interdisciplinary framework developed in this thesis combines economics and water resources engineering methods, establishing a promising means of bridging the gap between bottom-up and top-down approaches and supporting the creation of cost-effective and equitable adaptation plans at the local level. / [ES] La adaptación a los múltiples aspectos del cambio global supone un reto para los enfoques convencionales de planificación y gestión sostenible de los recursos hídricos a escala de cuenca. Numerosas opciones de gestión de la demanda o de la oferta están disponibles, de entre las cuales es necesario seleccionar medidas de adaptación en un contexto de elevada incertidumbre sobre las condiciones futuras. Dadas las interdependencias existentes entre los usuarios del agua a nivel local, hace falta buscar acuerdos a escala de cuenca para implementar las medidas de adaptación más eficaces. Por este motivo, esta tesis desarrolla una metodología que, combinando economía e ingeniería de los recursos hídricos, busca seleccionar un programa de medidas coste-eficaz frente a las incertidumbres del cambio climático, y asimismo definir un reparto justo del coste de la adaptación entre los actores implicados. El marco metodológico ha sido desarrollado para integrar contribuciones de los dos principales enfoques utilizados para la planificación de la adaptación. El primero, denominado descendente ("top-down"), consiste en una cadena de modelación que va desde los escenarios de emisiones de gases efecto invernadero a nivel global hasta los modelos hidrológicos utilizados a nivel local para evaluar así el impacto del cambio climático sobre los recursos hídricos. Por el contrario, el segundo enfoque denominado ascendente ("bottom-up") empieza por evaluar la vulnerabilidad del sistema a nivel local para después identificar medidas de adaptación frente a un futuro incierto. Los resultados de los métodos mencionados previamente se han integrado con el fin de seleccionar una combinación coste-eficaz de medidas de adaptación a través de un modelo de optimización a menor coste a escala de cuenca. El modelo se utiliza para investigar las soluciones de compromiso ("trade-offs") entre diversos objetivos de planificación como son los caudales ecológicos necesarios, el desarrollo del regadío y el coste del programa de medidas. Seguidamente, se han evaluado los programas de adaptación frente a varias condiciones climáticas para definir así un programa de medidas robusto y de arrepentimiento mínimo frente al cambio climático. En la última parte se aborda el problema del reparto justo de los costes del plan de adaptación, entendiendo que esto es una manera de favorecer su implementación. Para ello, se han modelado los resultados de un proceso de negociación entre los diferentes actores mediante escenarios de reparto basados en la teoría de juegos cooperativos. Posteriormente, se han comparado estos resultados con otras reglas de reparto de costes basadas en principios de justicia social, proporcionando así un punto de vista diferente al proceso de negociación. Este novedoso enfoque ha sido aplicado a una cuenca mediterránea, la cuenca del rio Orb (Francia). Para ello, se han empleado proyecciones climáticas a medio-plazo de datos reescalados de 9 Modelos de Circulación Global. Además, se han desarrollado escenarios de evolución de la demanda en los sectores urbano y agrícola para el horizonte de planificación de 2030. El modelo de optimización a menor coste a escala de cuenca desarrollado en GAMS permite seleccionar un programa de medidas, de entre las 462 medidas de gestión de la oferta o de la demanda. Nueve escenarios de reparto de costes basados en diferentes principios de justicia social han sido debatidos con informantes clave mediante entrevistas y comparados con conceptos de solución de la teoría de juegos cooperativos, considerando un juego de 3 jugadores a escala de cuenca. El marco interdisciplinario desarrollado durante esta tesis combina métodos de economía y de ingeniería de los recursos hídricos de manera prometedora y permite integrar los enfoques "top-down" y "bottom-up", contribuyendo a definir un plan de adaptación coste-eficaz y justo a nivel local. / [CA] L'adaptació als múltiples aspectes del canvi global implica un repte per als enfocaments convencionals de planificació i gestió sostenible dels recursos hídrics a escala de conca. Existeixen nombroses opcions de gestió de la demanda y de la oferta. De entre elles, cal seleccionar mesures d'adaptació en un context d'incertesa elevada sobre les condicions futures. Donades les interaccions entre els usuaris de l'aigua a nivell local, és necessari buscar acords a escala de conca per tal d'implementar les mesures d'adaptació més eficaces. Per aquest motiu, la tesi desenvolupa una metodologia que, mitjançant la combinació d'economia i enginyeria dels recursos hídrics, siga adient per seleccionar un programa de mesures cost-eficaç per a fer front a les incerteses del canvi climàtic i, a més a més, definir un repartiment just del cost d'adaptació entre els actors implicats. El marc metodològic ha estat desenvolupat amb el fi de permetre integrar contribucions del principals enfocaments que s'utilitzen per a la planificació de l'adaptació. El primer, que es denomina descendent ("top-down"), consisteix a una cadena de modelació que va des dels escenaris d'emissions de gas d'efecte hivernacle a nivell global fins als models hidrològics a nivell local per avaluar l'impacte del canvi climàtic sobre els recursos hídrics. Per contra, el segon enfocament, que es denomina ascendent ("bottom-up"), comença per avaluar la vulnerabilitat del sistema a nivell local per a tot seguit identificar mesures d'adaptació de cara a un futur incert. Els resultats del mètodes esmentats prèviament, s'han integrat per a seleccionar una combinació de mesures d'adaptació cost-eficaç mitjançant un model d'optimització a menor cost a escala de conca. El model s'utilitza per investigar les solucions de compromís ("trade-offs") entre els diversos objectius de planificació, com són els cabals ecològics necessaris, el desenvolupament del regadiu i el cost del programa de mesures. A continuació, s'avaluen els programes d'adaptació per a varies condicions climàtiques amb el fi de definir un programa de mesures robust i de penediment mínim per a fer front al canvi climàtic. En la darrera part, s'escomet el problema del repartiment just dels costs del pla d'adaptació, considerant que això és una manera de facilitar la implementació del pla. En conseqüència, els resultats d'un procés de negociació entre els diferents actors han estat modelats mitjançant escenaris de repartiment basats en la teoria de jocs cooperatius. Tot seguit, els resultats s'han comparat amb altres regles de repartiment de costos basades en principis de justícia social. Això ha proporcionat un punt de vista diferent al procés de negociació. Aquest enfocament innovador s'ha aplicat a una conca mediterrània, la conca del riu Orb (França). Amb aquesta finalitat s'han utilitzat projeccions climàtiques a mig termini de dades reescalades de 9 Models de Circulació Global (MCG). A més a més, s'han desenvolupat escenaris d'evolució de la demanada en els sectors agrícola i urbà per a l'horitzó de planificació de 2030. El model d'optimització a menor cost a escala de conca desenvolupat en GAMS permet seleccionar un programa de mesures, de entre les 462 mesures de gestió de la oferta o de la demanda. Els nou escenaris de repartiment de costs han estat debatuts amb informants clau, mitjançant entrevistes, i comparats amb conceptes de solució de la teoria de jocs cooperatius, considerant un joc de 3 jugadors a escala de conca. El marc interdisciplinari desenvolupat al llarg de la tesi combina mètodes d'economia i d'enginyeria dels recursos hídrics de manera prometedora i permet la integració d'enfocaments "top-down" i "bottom-up", fet que contribueix a definir un pla d'adaptació cost-eficaç i just a escala local. / Girard, CDP. (2015). Integrating top-down and bottom-up approaches to design a cost-effective and equitable programme of measures for adaptation of a river basin to global change [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59461 / TESIS / Premios Extraordinarios de tesis doctorales

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study investigates the crustal structure, and assesses the qualitative and quantitative impacts of crust-mantle dynamics on subsidence pattern, past and present-day thermal field and petroleum system evolution at the southern South African continental margin through the application of a multi-disciplinary and multi-scale geo-modelling procedure involving both conceptual and numerical approaches. The modelling procedure becomes particularly important as this margin documents a complex interaction of extension and strike-slip tectonics during its Mesozoic continental rifting processes. Located on the southern shelf of South Africa, the Western Bredasdorp Basin (WBB) constitutes the focus of this study and represents the western section of the larger Bredasdorp sub-basin, which is the westernmost of the southern offshore sub-basins. To understand the margin with respect to its present-day structure, isostatic state and thermal field, a combined approach of isostatic, 3D gravity and 3D thermal modelling was performed by integrating potential field, seismic and well data. Complimenting the resulting configuration and thermal field of the latter by measured present-day temperature, vitrinite reflectance and source potential data, basin-scale burial and thermal history and timing of source rock maturation, petroleum generation, expulsion, migration and accumulation were forwardly simulated using a 3D basin modelling technique. This hierarchical modelling workflow enables geologic assumptions and their associated uncertainties to be well constrained and better quantified, particularly in three dimensions. At present-day, the deep crust of the WBB is characterised by a tripartite density structure (i.e. prerift metasediments underlain by upper and lower crustal domains) depicting a strong thinning that is restricted to a narrow E-W striking zone. The configuration of the radiogenic crystalline crust as well as the conductivity contrasts between the deep crust and the shallow sedimentary cover significantly control the present-day thermal field of the study area. In all respects, this present-day configuration reflects typical characteristics of basin evolution in a strike-slip setting. For instance, the orientations of the deep crust and fault-controlled basin-fill are spatially inconsistent, thereby indicating different extension kinematics typical of transtensional pull-apart mechanisms. As such, syn-rift subsidence is quite rapid and short-lived, and isostatic equilibrium is not achieved, particularly at the Moho level. Accompanied syn-rift rapid subsidence and a heat flow peak led to petroleum preservation in the basin since the Early Cretaceous. Two additional post-rift thermal anomalies related to the Late Cretaceous hotspot mechanism and Miocene margin uplift in Southern Africa succeeded the syn-rift control on maturation. This thermal maturity of the five mature source rocks culminated in four main generation and three main accumulation phases which characterise the total petroleum systems of the WBB. The Campanian, Eocene and Miocene uplift scenarios episodically halted source maturation and caused tertiary migration of previously trapped petroleum. Petroleum loss related to the spill point of each trap configuration additionally occurs during the Late Cretaceous-Paleocene and Oligocene-Early Miocene. The timing and extent of migration dynamics are most sensitive to the geological scenario that combined faulting, intrusive seal bypass system and facies heterogeneity. In fact, for models that do not incorporate facies heterogeneity, predicted past and present-day seafloor leakage of petroleum is largely underestimated. This complex interplay of generation and migration mechanisms has significant implications for charging of petroleum accumulations by multiple source rocks. Due to early maturation and late stage tertiary migration, the syn-rift source rocks particularly Mid Hauterivian and Late Hauterivian source intervals significantly control the extent of petroleum accumulation and loss in the basin. Lastly, the modelled 3D crustal configuration and Mezosoic to Cenozoic thermal regime of the WBB dispute classic uniform lithospheric stretching for the southern South African continental margin. Rather, this PhD thesis confirms that differential thinning of the lithosphere related to a transtensional pull-apart mechanism is the most appropriate for accurately predicting the evolution of basin and petroleum systems of the margin. Also, the presented 3D models currently represent the most advanced insights, and thus have clear implications for assessing associated risks in basin and prospect evaluation of the margin as well as other similar continental margins around the world. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die korsstruktuur en evalueer die kwalitatiewe en kwantitatiewe impakte van kors-mantel-dinamika op insinkingspatroon, die termiese veld en petroleumstels evolusie aan die suidelike Suid-Afrikaanse kontinentale grens, in die hede en die verlede, deur die toepassing van ’n multidissiplinêre en multiskaal-geomodelleringsprosedure wat beide konseptuele en numeriese benaderings behels. Die modelleringsprosedure veral is belangrik aangesien hierdie kontinentale grens ’n komplekse interaksie van uitbreidings- en strekkingsparallelle tektoniek gedurende die Mesosoïese vastelandskeurprosesse daarvan dokumenteer. Omdat dit op die suidelike platvorm van Suid-Afrika geleë is, maak die Westelike Bredasdorp Kom (WBK) die fokus van hierdie studie uit, en verteenwoordig dit die westelike deel van die groter Bredasdrop-subkom, wat die verste wes is van die suidelike aflandige subkomme. Om die grens met betrekking tot sy huidige struktuur, isostatiese staat en termiese veld te verstaan, is ’n kombinasie benadering bestaande uit isostatiese, 3D-gravitasie- en 3D- termiese modellering gebruik deur potensiëleveld-, seismiese en boorgatdata te integreer Ondersteunend totot die gevolglike konfigurasie en termiese veld van die laasgenoemde deur middel van hedendaagse temperatuur, soos gemeet, vitriniet-refleksiekoëffisiënt en bronpotensiaal data, komskaal-begrawing en termiese geskiedenis en tydsberekening van brongesteentematurasie, is petroleumgenerasie, -uitwerping, -migrasie en -akkumulasie in die toekoms gesimuleer deur gebruik te maak van ’n 3D-kommodelleringstegniek. Hierdie hierargiese modelleringswerkvloei maak dit moontlik om geologiese aannames en hulle geassosieerde onsekerhede goed aan bande te lê en beter te kwantifiseer, veral in drie dimensies. In die hede word die diep kors van die WBK gekarakteriseer deur ’n drieledige digtheidstruktuur (met ander woorde voorrift-metasedimente onderlê deur bo- en benedekors domeine) wat dui op ’n baie wesenlike verdunning, beperk tot ’n dun O-W-strekkingsone. Die konfigurasie van die radiogeniese kristallyne kors, sowel as die konduktiwiteitskontraste tussen die diep kors en die vlak sedimentêre dekking, beheer grotendeels die hedendaagse termiese veld van die studiearea. Hierdie hedendaagse konfigurasie weerspieël in alle opsigte tipiese eienskappe van kom-evolusie in ’n skuifskeur omgewing. Byvoorbeeld, Die oriëntasies van die diep kors en verskuiwingbeheerde komsedimentasie byvoorbeeld is ruimtelik inkonsekwent en dui daardeur op verskillende ekstensiekinematika, tipies van transtensionale tensiemeganisme. As sulks, is sin-rift-versakking taamlik vinnig en kortstondig, en word isostatiese ekwilibrium nie by die Moho-vlak, in die besonder, bereik nie. Samehangende sin-rift vinnige versakking en hittevloeihoogtepunt het gelei tot petroleum behoud in die kom sedert die vroeë Kryt. Twee bykomende post-rift termiese anomalieë wat verband hou met die laat Kryt-“hotspot” meganisme en die Mioseense kontinentale grensopheffing in Suidelike Afrika het die sin-rift-beheer met maturasie opgevolg. Hierdie termiese maturiteit van die vyf gematureerde brongesteentes het in vier hoofgenerasie- en drie hoofakkumulasie fases, wat die totaliteit van die petroleumstelsels van die WBK karakteriseer, gekulmineer. Die Campaniese, Eoseense en Mioseense opheffings senarios het episodies bronmaturasie gestop en tersiêre migrasie van petroleum wat vroeër opgevang was veroorsaak. Addisioneel vind petroleumverlies gekoppel aan die spilpunt van elke opvanggebiedkonfigurasie tydens die laat Kryt-Paleoseen en Oligoseenvroeë Mioseen plaas. Die tydstelling en omvang van migrasiedinamika is die sensitiefste vir die geologiese scenario wat verskuiwing, seëlomseilingstelsel en fasiesheterogeniteit kombineer. Trouens, vir modelle wat nie fasiesheterogeniteit inkorporeer nie, is voorspellings van vroeëre en huidige seebodemlekkasie van petroleum grotendeels onderskattings. Hierdie komplekse wisselwerking van generasie- en migrasiemeganismes het beduidende implikasies vir die laai van petroleumakkumulasies deur veelvoudige brongesteentes. Vanweë vroeë maturasie en laatstadiumtersiêre migrasie, oefen die sin-rift-brongesteentes, veral middel Hauterivium- en laat Hauteriviumbronintervalle, beduidende beheer oor die omvang van petroleumakkumulasie en -verlies in die kom uit. Laastens weerspreek die gemodelleerde 3D-korskonfigurasie en Mesosoïese-tot-Senosoïesetermiese regime van die WBK ’n klassieke uniforme litosferiese rekking vir die suidelike Suid- Afrikaanse kontinentale grens. Inteendeel, hierdie PhD-proefskrif bevestig dat ’n differensiële verdunning van die litosfeer, gekoppel aan ’n transtensiemeganisme, die beste geskik is om ’n akkurate voorspelling oor die evolusie van kom- en petroleumstelsels van die kontinentale grens mee te maak. Verder, verteenwoordig die 3D-modelle, wat hier aangebied word, tans die mees gevorderde insigte, en het hierdie modelle dus duidelike implikasies vir die assessering van verwante risiko’s in kom- en petroleum teikene valuering van die kontinentale grens, so wel as van ander soortgelyke kontinentale grense regoor die wêreld.