Master of Science / Department of Geology / Matthew Totten / Petroleum producing areas within the mid-continent region discovered in the first half of the 1900’s often ignored the potential of deeper horizons once hydrocarbons were discovered in shallower zones. In Ness County, Kansas the deepest horizon typically explored are Mississippian-aged rocks. One of the largest fields in Ness County is the Aldrich Field, first discovered in 1929. The Mississippian in this field contains an active water-drive, which was produced by an “open-hole” completion method. This precluded drilling deeper horizons. Although modern drilling and completion techniques allow drilling through and isolating water-drive reservoirs like the Mississippian, very few deep exploratory wells have been drilled in Ness County. Wells that penetrate sub-Mississippian horizons are typically drilled as disposal wells, along the flanks of the main structure. This study evaluates the potential of several sub-Mississippian formations to be hydrocarbon reservoirs. Drill cuttings from five wells that penetrate these formations were analyzed using a combination of petrographic microscope, Scanning Electron Microscope (SEM), and chemical methods. Reservoir quality porosity was observed in several sub-Mississippian zones. The presence of hydrocarbon staining was observed in the Viola samples of three wells, and the Arbuckle in one well. Staining was confirmed by EDS spectra under the SEM. The results of this study suggest a good potential of zones deeper than normally drilled to contain hydrocarbons in rocks with reservoir quality porosity. These zones were not drill stem tested in the Aldrich field, and structural advantage to these wells might be expected by drilling the apex of the trapping anticline to further evaluate the deeper horizons.

In the next 20 years, the global demand for oil is forecast to grow by 0.7% every year, and the demand for natural gas will increase by 1.6% annually. But as we continue to produce oil and gas, the resources of our current oilfields are depleting. To meet the rising global energy demand, it is essential that we can keep discovering more petroleum resources in the future. The primary aim of this PhD project is to deepen our understanding of hydrocarbon reservoirs and enhance our ability to explore. The first project looked at the geological risks in hydrocarbon exploration. It reviewed and statistically analysed the data of 382 unsuccessful boreholes in the UK offshore area. The results suggest that the most significant risk for an exploration well is encountering a thin or absent target reservoir. This risk happened to 27 ± 4% of the past unsuccessful wells. The following most common risks are low-porosity reservoirs (22 ± 4% of all cases) and the lack of a closed trap (23 ± 4%). The probability of a target reservoir having a leaky caprock is 5 ± 2%. The study has calculated the probability of occurrence of all the geological risks in exploration, and this risk data can be applied to predict the potential geological risks in future exploration. One challenge in developing saline aquifers as CO2 storage reservoirs is the lack of subsurface data, unless a well has been drilled. Drawing on the experience of hydrocarbon exploration, a potential CO2 storage site identified on seismic profiles will be subject to many uncertainties, such as thin or low-porosity reservoirs, leaky seals, which are analogue to the geological risks of an undrilled hydrocarbon prospect. Since the workflow of locating CO2 storage reservoirs is similar to the exploration for hydrocarbon reservoirs, the risk data of hydrocarbon exploration wells can be applied to infer the geological risks of the exploration wells for CO2 storage reservoirs. Based on this assumption, the study of Chapter 3 estimated that the probability of a borehole encountering a reservoir suitable for CO2 storage is c. 41-57% (90% confidence interval). For reservoirs with stratigraphic traps within the UKCS, the probability of success is slightly lower, at 39 ± 10% (90% confidence). Chapter 4 studies the porosity and diagenetic process of the Middle Jurassic Pentland Formation in the North Sea. The analysis data come from 21 wells that drilled and cored the Pentland Formation. Petrographic data suggest the content of detrital illite is the most important factor affecting the porosity of the Pentland Sandstone - the porosities of the sandstones with more than 15% of illite (determined by point-count) are invariably low (< 10%). Quartz cement grows at an average rate of 2.3 %/km below the depth of 2km, and it is the main porosity occluding phase in the deep Pentland Sandstone. Petrographic data shows the clean, fine-grained sandstones contain the highest amount of quartz cement. Only 1-2 % of K-feldspar seems to have dissolved in the deep Pentland Sandstone (> 2 km), and petrographic data suggest that K-feldspar dissolution does not have any substantial influence on the sandstone porosity. There is no geochemical evidence for mass transfer between the sandstones and shales of the Pentland Formation. Chapter 5 investigates the high porosity of the Pentland Sandstone in the Kessog Field, Central North Sea. The upper part of the Kessog reservoir displays an anomalously high porosity (c. 25 %, helium porosity) that is 10 % higher than the porosity of other Pentland sandstones at the same depth (c. 15 %, 4.1 - 4.4 km). Petrographic data show these high porosities are predominantly primary porosity. The effects of sedimentary facies, grain coats, secondary porosity and overpressure on the formation of the high porosity are considered to be negligible in this case. Early hydrocarbon emplacement is the only explanation for the high porosity. In addition to less quartz cement, the high-porosity sandstones also contain more K-feldspar and less kaolin than the medium-porosity sandstones of the same field. This indicates that early hydrocarbon emplacement has also inhibited the replacement of K-feldspar. The last chapter studies the potential mass transfer of silica, aluminium, potassium, iron, magenesium and calcium at sandstone-shale contacts. The study samples include 18 groups of sandstones and shales that were collected from five oilfields in the North Sea. The interval space between the samples of each group varies from centimetres to meters. The research aim is to find evidence of mass transfer by studying the samples' variation of mineralogy and chemistry as a function of the distance to the nearest sandstone-shale contact. The sandstones are mostly turbidite sandstones, and the shales are Kimmeridge Clay shales. Petrographic, mineralogical and chemical data do not provide firm evidence for mass transfer within any group of the samples. The result indicates that the scale of mobility of silica, aluminium, potassium, iron, magenesium and calcium in the subsurface may be below the scale of detection of the study method, i.e. < 5 cm.

Many hydrocarbon detection techniques have been developed for decades and one of the most efficient techniques for hydrocarbon exploration in recent years is well known as amplitude versus offset analysis (AVO). However, AVO analysis does not always result in successful hydrocarbon finds because abnormal seismic amplitude variations can sometimes be caused by other factors, such as alternative lithology and residual hydrocarbons in certain depositional environments. Furthermore, not all gas fields are associated with obvious AVO anomalies. Therefore, new techniques should be applied to combine with AVO for hydrocarbon detection. In my thesis, I, through case studies, intend to investigate and validate the wave decomposition technique as a new tool for hydrocarbon detection which decomposes seismic wave into different frequency contents and may help identify better the amplitude anomalies associated with hydrocarbon occurrence for each frequency due to seismic attenuation. The wavelet decomposition analysis technique has been applied in two geological settings in my study: clastic reservoir and carbonate reservoir. Results from both cases indicate that the wavelet decomposition analysis technique can be used for hydrocarbon detection effectively if the seismic data quality is good. This technique can be directly applied to the processed 2D and 3D pre-stack/post-stack data sets (1) to detect hydrocarbon zones in both clastic and carbonate reservoirs by analyzing the low frequency signals in the decomposed domain and (2) to identify thin beds by analyzing the high frequency signals in the decomposed domain. In favorable cases, the method may possibly help separate oil from water in high-porosity and high-permeability carbonate reservoirs deeply buried underground. Therefore, the wavelet analysis would be a powerful tool to assist geological interpretation and to reduce risk for hydrocarbon exploration.

Hydrocarbon exploration involves drilling into or near salt deposits in the Gulf of Mexico, Brazil, Egypt, and the Middle East. Drilling these systems has proven to be quite dangerous, challenging, and expensive due to the pressure and stress perturbations that exist around the salt. My study focuses on characterizing the pressure and stress distribution at the Mad Dog field, which is a large oil field below an allochthonous salt body in the deepwater Gulf of Mexico. The Mad Dog field lies beneath the Sigsbee Escarpment, which represents the surface and seaward-most indicator of a mobile salt in Green Canyon blocks 781, 782, 825, and 826, 190 miles southwest of New Orleans in 4,500-6,500 feet of water. I characterize the pressure distribution within the Lower Miocene sandstone reservoir which has produced over 100 million barrels to date. I map the reservoir horizon using 3D seismic data and that the reservoir is a complex regional anticlinal structure that is separated by numerous normal faults that cause it to be segmented into compartments. The in-situ pore pressures show that the compartments are not in pressure communication across the field and that multiple aquifer phase pressures are present. The in-situ pore pressure measurements are used to characterize the pressure distribution in the Miocene sediments below the salt body and in front of the mobile salt body. These measurements show that between the upper Miocene to middle Miocene there is an absolute pressure decrease and between the middle to lower Miocene there is a large pressure increase. This pressure distribution is seen both within the Miocene sediments below salt and in front of salt. A porosity and effective stress relationship from shallow Pleistocene sediments was developed to predict the pressure behavior observed within the Miocene and compare the predicted pressure with in-situ pore pressure measurements. The mudstone pressure prediction overestimates the in-situ sand pore pressure. The mudstones bounding regional sandstone have a constant porosity throughout the field, suggesting that the vertical effective stress is constant. These observations can be used to estimate the mudstone pore pressure in a new well location. If the vertical effective stress in an offset well is known and given knowledge of the total vertical stress in the new well location, the mudstone pore pressure can be estimated. / text

Tesis por compendio / [EN] Social impact assessment (SIA) is a part of environmental impact assessment (EIA), which is characterized by a high level of uncertainty and the subjective aspects that are presents in the methods used during its conduction. In addition, environmental conflict analysis (ECA) has become a key factor for the viability of projects and welfare of affected populations. In this thesis, an integrated method for SIA and ECA is proposed, by the combination of the grey clustering method and the entropy-weight method. SIA was performed using the grey clustering method, which enables qualitative information coming from a stakeholder group to be quantified. In turn, ECA was performed using the entropy-weight method, which identifies the criteria in which there is greater divergence between stakeholder groups, thus enabling to establish measures to prevent potential environmental conflicts. Then, in order to apply and test the proposed integrated method, two case studies were conducted. The first case study was a mining project in northern Peru. In this study, three stakeholder groups and seven criteria were identified. The results revealed that for the urban population group and the rural population group, the project would have a positive and negative social impact, respectively. For the group of specialists the project would have a normal social impact. It was also noted that the criteria most likely to generate environmental conflicts in order of importance were: access to drinking water, poverty, GDP per capita, and employment. The second case study considered was a hydrocarbon exploration project located in the Gulf of Valencia, Spain. In this study, four stakeholder groups and four criteria were identified. The results revealed that for the group of specialists the project would have a negative social impact, and contrary perceptions were shown between the group of those directly affected by the project and the group of citizens in favour. It was also noted that the criteria most likely to generate environmental conflict were the percentage of unemployment and GDP per capita. The proposed integrated method in this thesis showed great potential on the studied cases, and could be applied to other contexts and other projects, such as water resources management, industrial projects, construction projects, and to measure social impact and prevent conflicts during the implementation of government policies and programs. / [ES] La evaluación del impacto social (SIA) forma parte de la evaluación de impacto ambiental (EIA), y está caracterizada por su alto nivel de incertidumbre, y por los aspectos subjetivos presentes en los métodos usados para su realización. Por otro lado, el análisis del conflicto ambiental (ECA) se ha convertido en un factor clave para la viabilidad de los proyectos y el bienestar de la población afectada. En esta tesis, se propone un método integrado para la SIA y el ECA, mediante la combinación de los métodos grey clustering y entropy-weight. La SIA fue desarrollada usando el método grey clustering, el cual permite cuantificar la información cualitativa recogida de los grupos de interés o stakeholders. Sucesivamente, el ECA fue realizado usando el método entropy-weight, el cual identifica los criterios en los cuales existe gran divergencia entre los grupos de interés, permitiendo así establecer medidas para prevenir potenciales conflictos ambientales. Luego, con el fin de aplicar y testear el método integrado propuesto fueron realizados dos casos de estudio. El primer caso de estudio fue un proyecto minero ubicado en el norte de Perú. En este estudio se identificaron tres grupos de interés y siete criterios. Los resultados revelaron que para el grupo población urbana y el grupo población rural, el proyecto tendría un impacto social positivo y negativo, respectivamente. Para el grupo de los especialistas el proyecto tendría un impacto social normal. También fue notado que los criterios más probables de generar conflicto ambiental en orden de importancia fueron: acceso al agua potable, pobreza, PIB per cápita, y empleo. El segundo caso de estudio considerado fue un proyecto de exploración de hidrocarburos ubicado en el Golfo de Valencia, España. En este estudio se identificaron cuatro grupos de interés y cuatro criterios. Los resultados revelaron que para el grupo de los especialistas el proyecto tendría un impacto social negativo, y contrarias percepciones se encontraron entre el grupo de los directamente afectados y el grupo de los ciudadanos a favor. También fue notado que los criterios más probables de generar conflicto ambiental fueron el porcentaje de desempleo y el PIB per cápita. El método integrado propuesto en esta tesis mostró un gran potencial sobre los casos estudiados, y podría ser aplicado a otros contextos y otros tipos de proyectos, tales como gestión de recursos hídricos, proyectos industriales, proyectos de construcción de obras públicas, y para medir el impacto social y prevenir conflictos durante la aplicación de políticas y programas gubernamentales. / [CA] L'avaluació de l'impacte social (SIA) és una part de l'avaluació de l'impacte ambiental (EIA), la qual està caracteritzada pel seu alt nivell d'incertitud i els aspectes subjectius presents en els mètodes amprats durant la seua conducció. A més, la anàlisis del conflicte ambiental (ECA) s'ha convertit en un factor clau per a la viabilitat dels projectes i el benestar de la població afectada. En esta tesis es proposa un mètode integrat per a l'avaluació de l'impacte social i la anàlisis del conflicte ambiental, mitjançant la combinació del mètode grey clustering i el mètode entropy-weight. L'avaluació de l'impacte social ha segut realitzada usant el mètode grey clustering, el qual permet que la informació qualitativa arreplegada dels grups d'interès siga quantificada. Successivament, la anàlisis del conflicte ambiental ha segut realitzada usant el mètode entropy-weight, el qual identifica els criteris en els quals existeix gran divergència entre els grups d'interès, la qual cosa permet establir mides per a prevenir conflictes ambientals potencials. Després, amb la finalitat d'aplicar i testejar el mètode integrat proposat han segut realitzats dos casos d'estudi. El primer d'ells ha segut un projecte miner al nord de Perú. En aquest estudi, tres grups d'interès i set criteris foren identificats. Els resultats revelaren que per al grup població-urbana i el grup població-rural, el projecte experimentaria un positiu i un negatiu impacte social respectivament. Per al grup dels especialistes el projecte tindria un impacte social normal. Per altra banda també va ser reconegut que els criteris més probables de generar conflicte ambiental en orde d'importància foren: accés a l'aigua potable, pobresa, PIB per càpita, i ofici. El segon cas d'estudi considerat va ser un projecte d'exploració d'hidrocarburs ubicat al Golf de València, Espanya. En este estudi, quatre grups d'interès i quatre criteris foren identificats. Els resultats revelaren que per al grup dels especialistes el projecte tindria un impacte social negatiu, mentre que entre el grup dels directament afectats i el grup dels ciutadans a favor es mostraren percepcions contraries. Va ser també reconegut que els criteris més probables de generar conflicte ambiental foren el percentatge de desocupació i el PIB per càpita. El mètode integrat proposat en aquesta tesis mostra un gran potencial sobre els casos estudiats, i pot ser aplicat a altres contexts i altres tipus de projectes com gestió de recursos hídrics, projectes industrials i projectes de construcció d'obres públiques. A més pot fer-se servir per mesurar l'impacte social i prevenir conflictes durant l'aplicació de polítiques i programes governamentals. / Delgado Villanueva, KA. (2016). Methodological proposal for social impact assessment and environmental conflict analysis [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64063 / Compendio

The primary focus of this thesis is to examine the detailed seismic structure of the northern Cascadia margin, including the Cascadia basin, the deformation front and the continental shelf. The results of this study are contributing towards understanding sediment deformation and tectonics on this margin. They also have important implications for exploration of hydrocarbons (oil and gas) and natural hazards (submarine landslides, earthquakes, tsunamis, and climate change). The first part of this thesis focuses on the role of gas hydrate in slope failure observed from multibeam bathymetry data on a frontal ridge near the deformation front off Vancouver Island margin using active-source ocean bottom seismometer (OBS) data collected in 2010. Volume estimates (∼ 0.33 km^3) of the slides observed on this margin indicate that these are capable of generating large (∼ 1 − 2 m) tsunamis. Velocity models from travel time inversion of wide angle reflections and refractions recorded on OBSs and vertical incidence single channel seismic (SCS) data were used to estimate gas hydrate concentrations using effective medium modeling. Results indicate a shallow high velocity hydrate layer with a velocity of 2.0 − 2.1 km/s that corresponds to a hydrate concentration of 40% at a depth of 100 m, and a bottom simulating reflector (BSR) at a depth of 265 − 275 m beneath the seafloor (mbsf). These are comparable to drilling results on an adjacent frontal ridge. Margin perpendicular normal faults that extend down to BSR depth were also observed on SCS and bathymetric data, two of which coincide with the sidewalls of the slump indicating that the lateral extent of the slump is controlled by these faults. Analysis of bathymetric data indicates, for the first time, that the glide plane occurs at the same depth as the shallow high velocity layer (100±10 mbsf). In contrast, the glide plane coincides with the depth of the BSR on an adjacent frontal ridge. In either case, our results suggest that the contrast in sediments strengthened by hydrates and overlying or underlying sediments where there is no hydrate is what causing the slope failure on this margin. The second part of this dissertation focuses on obtaining the detailed structure of the Cascadia basin and frontal ridge region using mirror imaging of few widely spaced OBS data. Using only a small airgun source (120 cu. in.), our results indicate structures that were previously not observed on the northern Cascadia margin. Specifically, OBS migration results show dual-vergence structure, which could be related to horizontal compression associated with subduction and low basal shear stress resulting from over-pressure. Understanding the physical and mechanical properties of the basal layer has important implications for understanding earthquakes on this margin. The OBS migrated image also clearly shows the continuity of reflectors which enabled the identification of thrust faults, and also shows the top of the igneous oceanic crust at 5−6 km beneath the seafloor, which were not possible to identify in single-channel and low-fold multi-channel seismic (MCS) data. The last part of this thesis focuses on obtaining detailed seismic structure of the Vancouver Island continental shelf from MCS data using frequency domain viscoacoustic full waveform inversion, which is first of its kind on this margin. Anelastic velocity and attenuation models, derived in this study to subseafloor depths of ∼ 2 km, are useful in understanding the deformation within the Tofino basin sediments, the nature of basement structures and their relationship with underlying accreted terranes such as the Crescent and the Pacific Rim terranes. Specifically, our results indicate a low-velocity zone (LVZ) with a contrast of 200 m/s within the Tofino basin sediment section at a depth 600 − 1000 mbsf over a lateral distance of 10 km. This LVZ is associated with high attenuation values (0.015 − 0.02) and could be a result of over pressured sediments or lithology changes associated with a high porosity layer in this potential hydrocarbon environment. Shallow high velocities of 4 − 5 km/s are observed in the mid-shelf region at depths > 1.5 km, which is interpreted as the shallowest occurrence of the Eocene volcanic Crescent terrane. The sediment velocities sharply increase about 10 km west of Vancouver Island, which probably corresponds to the underlying transition to the Mesozoic marine sedimentary Pacific Rim terrane. High attenuation values of 0.03 − 0.06 are observed at depths > 1 km, which probably corresponds to increased clay content and the presence of mineralized fluids. / Graduate / 0373 / 0372 / 0605 / subbarao@uvic.ca