The effect of Vshale 3D distribution on the secondary migration of hydrocarbons.

This thesis discusses some topics related to the Petroleum System Modeling, a geology field of study that deals with simulation of various petroleum system elements in order to evaluate amount and type of potential hydrocarbons accumulations. In particular, this study is based on Migri, a software which aims to simulate hydrocarbons paths and accumulations linked with secondary migration process. In spite of this kind of studies have already been performed with other software, the aim of this work has been to approach a new methodology, using data that have never been considered in Eni for secondary migration simulation: in fact, this is the first time in which the flow has been considered into a 3D model lithologically defined. As a first approach, tests have been performed in order to understand how the formation shale volume (Vsh) could influence the hydrocarbon flow, and consequently the accumulations. This information started with Vsh values acquisition from gamma ray logs, carried out in correspondence of 32 wells. These values have been interpolated thanks to geostatistic methods, in order to build Vsh distribution maps for each layer interested by secondary migration processes. In particular, tests were performed on the basis of four different Vsh distribution scenarios. Obtained results represent a good starting point in the study of this software. In fact, in addition to information about the direct influence of Vsh in the model, it has been possible to understand that the results accuracy is strongly linked with the starting GeoModel quality.ope

From gravity cores to overpressure history: the importance of measured sediment physical properties in hydrogeological models

The development of overpressure in continental margins is typically evaluated with hydrogeological models. Such approaches are used to both identify fluid flow patterns and to evaluate the development of high pore pressures within layers with particular physical properties that may promote slope instability. In some instances, these models are defined with sediment properties based on facies characterization and proxy values of porosity, permeability or compressibility are derived from the existing literature as direct measurements are rarely available. This study uses finite-element models to quantify the differences in computed overpressure generated by fine-grained hemipelagic sediments from Gulf of Cadiz, offshore Martinique and Gulf of Mexico, and their consequences in terms of submarine slope stability. By comparing our simulation results with in-situ pore pressure data measured in the Gulf of Mexico, we demonstrated that physical properties measured on volcanic-influenced hemipelagic sediments underestimate the computed stability of a submarine slope. Physical properties measured on sediments from the study area are key to improving the reliability and accuracy of overpressure models, and when that information is not available literature data from samples with similar lithologies, composition and depositional settings enable better assessment of the overpressure role as a pre-conditioning factor in submarine landslide initiation

Caracterización de grandes estructuras sismogénicas y tsunamogénicas del Golfo de Cádiz con tecnologías de muy alta resolución : Cruise Report INSIGHT-Leg 1

Cruise Report INSIGHT-Leg 1 R/V Sarmiento de Gamboa (SDG-68) 29th April - 18th May 2018.-- 139 pages, figures, tables, 2 annexesLarge earthquakes, submarine landslides and the tsunami they might originate are geohazards of great societal concern because they may impact world economies and struck coastal populations. Examples of these events are the 2004 northern Sumatra and 2011 Tohoku earthquakes and respective tsunamis. However, earthquakes of magnitude Mw > 8.0 in areas of relatively slow tectonic deformation and with long recurrence intervals, such as the external part of the Gulf of Cadiz, might also have a significant impact. The most relevant is the 1755 Lisbon earthquake, related submarine landslides and destructive tsunami. The occurrence of faults and landslides able to trigger a catastrophic tsunami reveals that the Gulf of Cadiz is one of the highest geohazard areas in Europe. Migration of sub-seafloor fluids has also been widely documented in the Gulf of Cadiz and such fluids are strongly related to the earthquake cycle and to the occurrence of submarine landslides. Understanding of these active processes can only be developed by using ultra-high-resolution tools able to map with unprecedented detail faults, submarine landslides and fluid escape structures. State-of-the-art techniques are used during INSIGHT-Leg 1, such as microbathymetry obtained from an autonomous underwater vehicle (AUV), sub-bottom profiles, HR multi-channel seismic data (MCS), and groundtruthing using sediment coresWe gratefully acknowledge financial support from Ministerio Economia y Competividad through national project INSIGHT “ImagiNg large SeismogenIc and tsunamiGenic structures of the Gulf of Cadiz with ultra-High resolution Technologies (INSIGHT-Leg1)” (CGL2011-30005-C02-02, PIs: Roger Urgeles and Eulàlia Gràcia) and Ocean Facilities Exchange Group (OFEG) for allowing us to use the AUVs “Abyss” from GEOMAR (Germany

Pore pressure build-up in mixed contourite-turbidite systems: the SW Iberian margin

[eng] Contourite drifts are the depositional expression of bottom currents, which are capable of shaping the morphology of the seafloor by transporting, eroding and reworking marine sediments, and are distributed on continental slopes worldwide. Synchronous interaction between bottom currents and turbidity currents have been reported often in channel-levée systems where the thickness of the turbidity current exceeds that of the levées. Such interplay between along-slope and down-slope sedimentary process is one of the mechanisms by which “mixed turbidite-contourite systems” can originate. Being composed by the winnowed finest part of turbidity currents and potentially able to deposit at sedimentation rates of several m/kyr, mixed systems constitute a potential source of overpressure development in marine sediments. The Alentejo basin is located in the northern edge of the Gulf of Cadiz (SW Iberian margin), from which is separated by the São Vicente Canyon, one of the most prominent geomorphological features in SW Iberia. The area is characterized by an extensive contourite depositional system, generated by the Mediterranean Outflow Water (MOW) bottom current. The Alentejo basin hosts multiple mass transport deposits (MTDs) and scars, which are typically considered to be triggered by the frequent seismic activity related to the movement of multiple active faults present in the area. The combined presence of a contourite depositional system, a deeply incised canyon, mass wasting processes and potentially seismogenic faults makes the Alentejo basin the ideal study area to assess: a) how does contour currents interact with sediments transported along deeply incised canyons? b) How does mixed contourite – turbidite systems affect the development of overpressure within marine sediments, and consequently the stability of submarine slopes? To answer these questions, in this thesis we first adopted a workflow that included reinterpretation of existing seismic data in the Alentejo basin as well as acquisition and interpretation of geophysical and sediment core data collected during two scientific cruises in 2018 (INSIGHT-Leg1) and 2019 (INSIGHT- Leg2). The study focuses in the area between ~ 1000 and 3000 m water depth around the São Vicente Canyon. Grain size and physical properties (i.e. water content, Atterberg limits, porosity, permeability and compression index) of sediments collected in the study area have been analysed through geotechnical laboratory experiments. The updated stratigraphic model and sediment physical properties have been integrated into Finite Element numerical models in order to derive the fluid flow and overpressure evolution of the Alentejo basin, focusing on the potential influence of mixed-system deposition in the emplacement of the MTDs detected in the basin and in the overall stability of the slopes. This thesis identifies a previously unknown mixed contour current – turbidity current deposit, the Marquês de Pombal Drift, located on the NW flank of the São Vicente Canyon and generated by the interaction between the MOW, particularly during cold periods, and turbidity currents flowing along the canyon itself. Because the canyon is incised significantly deeper (~ 1.5 km) than the thickness of turbidity currents, interaction between down-slope and along-slope currents requires intermediate nepheloid layers, forming at the boundary between major water masses (i.e., the MOW and the North Atlantic Deep Water), to export the finer-grained fraction of turbidity currents out of the canyon. Such mechanism is likely active in other canyons worldwide. Stratigraphic interpretation and gravity core analysis reveal that the Marquês de Pombal Drift is characterized by sedimentation rates up to 2 m/kyr and fine-grained sediments (mean grain size of 8.6 µm). Despite those characteristics, the hydrogeological models presented in this thesis show development of overpressure associated with the Marquês de Pombal Drift deposition up to a maximum of 20% of the lithostatic load. Factor of safety (FoS) analysis indicates that overpressure development decreases the stability of the slopes in the study area by 18% under static conditions, and that slope gradients play a more important role as pre- conditioning factor for slope failures as the highest overpressures are recorded in relatively flat terrains. The pseudo-static slope stability analysis, on the other hand, indicates that earthquake-induced accelerations given the fault characteristics in the area (i.e. earthquake shaking) have a much stronger influence on slope stability in the Alentejo basin. Therefore, trigger mechanisms seems to be the predominant component in slope stability compared to pre-conditioning factors (i.e., overpressure development, slope gradients). The results indicate that the Marquês de Pombal Drift is a relatively stable feature and its deposition has a minor influence in the stability of the Alentejo basin. However, in other settings, fine-grained sediments and potential high sedimentation rates associated with mixed contour current – turbidity current systems could have the potential to develop higher overpressure and thus play a more important role in submarine slope stability. Our results show that multiple conditions related with the physical properties of sediments (i.e. high degree of compressibility and low permeability), high sedimentation rate and the morphology of the slope (i.e. slope gradients) must all be present to efficiently influence slope instability

The effect of Vshale 3D distribution on the secondary migration of hydrocarbons.

This thesis discusses some topics related to the Petroleum System Modeling, a geology field of study that deals with simulation of various petroleum system elements in order to evaluate amount and type of potential hydrocarbons accumulations. In particular, this study is based on Migri, a software which aims to simulate hydrocarbons paths and accumulations linked with secondary migration process. In spite of this kind of studies have already been performed with other software, the aim of this work has been to approach a new methodology, using data that have never been considered in Eni for secondary migration simulation: in fact, this is the first time in which the flow has been considered into a 3D model lithologically defined. As a first approach, tests have been performed in order to understand how the formation shale volume (Vsh) could influence the hydrocarbon flow, and consequently the accumulations. This information started with Vsh values acquisition from gamma ray logs, carried out in correspondence of 32 wells. These values have been interpolated thanks to geostatistic methods, in order to build Vsh distribution maps for each layer interested by secondary migration processes. In particular, tests were performed on the basis of four different Vsh distribution scenarios. Obtained results represent a good starting point in the study of this software. In fact, in addition to information about the direct influence of Vsh in the model, it has been possible to understand that the results accuracy is strongly linked with the starting GeoModel quality

Did overpressures develop before the Marques de Pombal mass transport events happened?

34th International Association of Sedimentologists (IAS) Meeting of Sedimentology, Sedimentology to face societal challenges on risk, resources and record of the past, 10-13 September 2019, Rome.-- 1 pageThe hanging wall of the Marques de Pombal fault, in the Northern section of the Gulf of Cadiz (SW Iberian Margin), displays multiple slope failures, the most recent of which, the Marques de Pombal Mass Transport Complex (MTC), has an estimated volume of 1.3 km3. The location of the MTC, at the bottom of the Marques de Pombal active fault, suggests earthquake shaking as the most likely triggering mechanism for local mass wasting events. Moreover, the Marques de Pombal fault is considered by several authors as a possible candidate for the generation of the 1755 Great Lisbon catastrophic earthquake and tsunami event. Sediment distribution of the area is characterized by an extensive contourite depositional system related to the Mediterranean Outflow Water (MOW) that flows northward over the upper and middle part of the slope. IODP expedition 339 explored the stratigraphy of the Gulf of Cadiz by drilling 6 different wells in the area, one of which (Well 339-U1391) was drilled approximately 50 km away from the Marques de Pombal MTC. Furthermore, the INSIGHT cruise conducted by ICM – CSIC in May 2018 collected new seismic, bathymetric and gravity core data from the undisturbed sediments at the top of the Marques de Pombal fault scarp. The aim of this project is to investigate the contribution of excess pore pressure (pre-conditioning factor) versus earthquake cyclic loading (trigger mechanism) in the Marques de Pombal area, to understand pore pressure and slope stability evolution through time and make inferences about the magnitude of the events that triggered the failures. The workflow adopted in this study consists of integrating into finite element numerical models geotechnical data from the sediments collected during the INSIGHT cruise, such as initial porosity, compressibility and permeability, with a stratigraphic model of the basin derived from seismic profiles and well and log data from the IODP well 339-U139, in order to obtain the computed excess pore pressure history for the sediments in the Marques de Pombal area. Our modelling results show the development of mid-to-high overpressure values (up to 0.4), which started developing in the Middle Pleistocene and continued through the Holocene. Considering the not particularly high sedimentation rate of the contourite system in the middle part of the Marques de Pombal continental slope, we found the reasons of the overpressures development in the area in the physical properties of the sediments, and especially in their high compressibility. Assuming the Marques de Pombal fault as the main responsible for triggering the multiple MTC observed in the area, we can make some assumptions about the fault activity by comparing the ages of the deposits with overpressure modelling result

Pre-failure stress-state of an earthquake triggered submarine landslide: The Marques de Pombal landslide, offshore Portugal

20th International Sedimentological Congress (ISC), 13-17 August 2018, Quebec City, Canada.-- 1 pageThe Marques de Pombal landslide deposit, with its estimated volume of 1.3 km2, is located in the Alentejo Basin, the Northern section of the Gulf of Cadiz (SW Iberian Margin). Gravity core analyses sampled in the Marques de Pombal depositional area reveal that multiple landslide and turbidity events contributed to the deposit formation1,2. Considering the moderate-to-large-magnitude seismic activity of the area, earthquakes are the main triggering candidate for the mass wasting events. The Great Lisbon catastrophic earthquake of 1755 may also have contributed to the landslide’s deposit. This work reconstructs the sedimentary, stratigraphic and geotechnical conditions of the area of interest before the 1755 earthquake and aims to evaluate the development of excess pore pressure in order to balance pre-conditioning factors vs triggering mechanisms in onset of slope failure. Seismic profiles, swath bathymetry deep-towed side-scan sonar mosaics and well and log data from the IODP 339 expedition have been used to construct a stratigraphic model of the slope failure area. Gravity core samples are used to understand development of permeability, compressibility and strength with burial depth. These data are used to build a numerical finite elements model, which aims to determine the relationship between continental margin development and its hydrogeological evolutionThis work was supported and financed by the SLATE (H2020-MSCA-ITN-2016-721403)–“Submarine landslides and their impact on continental margins ”European Training Network and the Spanish project “ImagiNg large SeismogenuIc and tsunamiGenic structures of the Gulf of Cadiz with ultra-High resolution Technologies” (INSIGHT(CTM2015-70155-R)Peer Reviewe

Excess Pore Pressure Evolution of the Marques de Pombal ContinentalSlope, Offshore Portugal

European Geosciences Union (EGU) General Assembly, 7-12 April 2019, Vienna, Austria.-- 1 pageThe Marques de Pombal Mass Transport Complex (MTC) is located in the Alentejo Basin in the northern sector of the Gulf of Cadiz (SW Iberian Margin). Several geophysical studies and gravity core analyses over the last two decades reveal the contribution of multiple landslides and turbidity events in the formation of the MTC. The location of the MTC, at the base of the Marques de Pombal active fault, suggests fault activity as the most likely triggering mechanism for local mass wasting events. Moreover, the Marques de Pombal fault is considered by several authors as a possible candidate for the generation of the 1755 Great Lisbon catastrophic earthquake and tsunami event. The INSIGHT cruise conducted by ICM – CSIC in May 2018 collected new seismic, bathymetric and gravity core data from the study area, including undisturbed sediments at the top of the Marques de Pombal fault scarp. We performed consolidation tests to derive the evolution of porosity, permeability and compressibility of these sediments through time and at different burial conditions. The aim of this project is to evaluate the contribution of excess pore pressure (pre-conditioning factor) versus earthquake cyclic loading (trigger mechanism) in the Marques de Pombal area, to understand slope stability through time and make inferences about the magnitude of the seismic events that triggered the failures. We integrate into a finite element basin numerical model physical properties of the sediments collected during the INSIGHT cruise with a stratigraphic model of the basin derived from seismic profiles, swath bathymetry deep-towed side-scan sonar mosaics, and well and log data from the IODP 339 expedition. Starting from measured data, we obtained the computed excess pore pressure history for the sediments in the Marques de Pombal area. The results show how a significant lateral flow towards the Marques de Pombal fault scarp contributed to the generation of mid-to-high overpressures up to a value of 0.5, which started developing significantly in the Middle Pleistocene and continued during the Holocene. Since the timing of the overpressure development is in agreement with the occurrence of the Marques de Pombal MTC, we believe that excess pore pressure might have pre-conditioned the slope to failPeer reviewe

Assessing Submarine Slope Stability From Sediment Properties In The Gulf Of Cadiz, Offshore Portugal

American Geophysical Union (AGU) Fall Meeting, 9-13 December 2019, San FranciscoThe development of excess pore pressure in soft marine sediments is a major pre-conditioning factor for slope instabilities. Basin analysis and hydrogeological models are often the only options to evaluate present-day overpressure conditions as well as their evolution through time. We describe a workflow that integrates measured geotechnical data and interpreted stratigraphy into finite element hydrogeological models to obtain the computed excess pore pressure and slope stability history of the Marques de Pombal area, located offshore Portugal. The hanging wall of the Marques de Pombal fault displays multiple slope failures. The location of the mass transport complex at the bottom of the Marques de Pombal active fault suggests earthquake shaking as the most probable triggering mechanism for local mass wasting events. Nevertheless, the role of preconditioning factors such as pore pressure development needs to be weighed against seismic shaking. We integrated the stratigraphic model revealed by IODP Well 339-U1391, drilled approximately 50 km away from the study area, with new geophysical data and gravity cores collected from the INSIGHT cruises conducted by ICM – CSIC in 2018 and 2019. We measured geotechnical properties from the sediments collected in the study area, such as initial porosity, compressibility and permeability, and assigned them to 2D finite element slope stability models by using commercial geotechnical software, in order to obtain the computed excess pore pressure and slope stability history for the Marques de Pombal area. Besides providing a new approach to define regional hydrogeological models with measured sediment properties, our models’ results show mid-to-high overpressure ratio (up to 0.4) influencing the stability of the slope from the Middle Pleistocene until the present day. By comparing the ages of the deposits with the computed history of the slope’s stability, we are able to constrain the minimum earthquake magnitudes required to induce past slope failures and make inferences about potential future one

Assessing submarine slope stability from sediment properties in the Gulf of Cadiz, offshore Portugal

American Geophysical Union (AGU) Fall Meeting, 9-13 December 2019, San FranciscoThe development of excess pore pressure in soft marine sediments is a major pre-conditioning factor for slope instabilities. Basin analysis and hydrogeological models are often the only options to evaluate present-day overpressure conditions as well as their evolution through time. We describe a workflow that integrates measured geotechnical data and interpreted stratigraphy into finite element hydrogeological models to obtain the computed excess pore pressure and slope stability history of the Marques de Pombal area, located offshore Portugal. The hanging wall of the Marques de Pombal fault displays multiple slope failures. The location of the mass transport complex at the bottom of the Marques de Pombal active fault suggests earthquake shaking as the most probable triggering mechanism for local mass wasting events. Nevertheless, the role of preconditioning factors such as pore pressure development needs to be weighed against seismic shaking. We integrated the stratigraphic model revealed by IODP Well 339-U1391, drilled approximately 50 km away from the study area, with new geophysical data and gravity cores collected from the INSIGHT cruises conducted by ICM – CSIC in 2018 and 2019. We measured geotechnical properties from the sediments collected in the study area, such as initial porosity, compressibility and permeability, and assigned them to 2D finite element slope stability models by using commercial geotechnical software, in order to obtain the computed excess pore pressure and slope stability history for the Marques de Pombal area. Besides providing a new approach to define regional hydrogeological models with measured sediment properties, our models’ results show mid-to-high overpressure ratio (up to 0.4) influencing the stability of the slope from the Middle Pleistocene until the present day. By comparing the ages of the deposits with the computed history of the slope’s stability, we are able to constrain the minimum earthquake magnitudes required to induce past slope failures and make inferences about potential future one