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Optimizing the extraction of oil and other hydrocarbon products from existing sites is important. One source of hydrocarbon products is reservoirs found within sedimentary rock formations. Understanding fluid behavior within such formations can be quite useful in optimizing oil production. Fluid behavior within sedimentary formations is influenced by the bedform structure and permeabilities within the formation. Thus, we are concerned with developing a physically and statistically valid method of characterizing sedimentary rock formations. The use of archetypal analysis to generate synthetic bedforms, as well as the use of Kriging to assign permeabilities within a bedform, was explored. With these tools, a characterization of a sedimentary rock formation can be created and fluid flow through the charactrerization examined. It appears that the bedform structure within a realization has a greater influence on fluid flow than any permeability structure created by utilizing Kriging.

Earlier researchers have produced conceptual models of Mississippi River delta plain development which divide the deltaic plain into upper and lower reaches. The upper deltaic plain has been described as an area composed mainly of lacustrine, lacustrine delta, backswamp, and crevasse channels, with minimal distributary development. The lower deltaic plain is characterized by numerous distributaries forming distributary systems and lobes. Detailed geomorphic mapping and chronologic reconstruction within the Atchafalaya Backwater Area of the upper deltaic plain of the Mississippi River has led to the recognition of a complex network of distributary development related to three distinct distributary systems that formed in the upper deltaic plain over the past 2500 years. These systems do not fit previous models of upper deltaic plain development. The East Atchafalaya Basin Protection Levee blocked Atchafalaya River water and sediment from entering the study area and burying these older distributary systems, preserving their surface expression and allowing their identification. Results show that distributary systems can be a major contributor to upper deltaic plain development and that these systems are not always related to the lower delta plain delta switching process. A stable Mississippi River position and a favorable gradient in the study area over the past 4,000 years appear to be responsible for the geomorphic development of the study area.

Thesis advisor: Douglas Edmonds / Due to their low-lying position near the shoreline, river deltas are vulnerable to fluctuations in relative sea-level (RSL). Moreover, relatively little is known about fluvio-deltaic dynamics during RSL fall because the resulting deposits have low preservation potential. In this paper, I present a field-based study of the Goose River delta, coupled with numerical model simulations, that investigates the fluvio-deltaic response to RSL fall. The Goose River delta is a sandy fjord delta at the mouth of the Goose River located at the western end of Lake Melville, an inlet of the Labrador Sea, Canada and has experienced a RSL fall of 3 to 6 mm/yr in the past 5000 years due to post-glacial isostatic rebound. Aerial images show three abandoned delta lobes and one active lobe, suggesting that avulsions and lobe-switching occurred during RSL fall. Elevation analysis using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data and optically-stimulated luminescence (OSL) dating suggest that a series of downstepping terraced delta lobes formed at the mouth of the Goose River during a period of RSL fall. Similarly, Delft3D model runs show continued avulsions and formation of multiple terraced delta lobes deposited at progressively lower elevations. I show computationally that by decreasing delta lobe widths, deltas may remain aggradational during RSL fall, creating conditions favorable for lobe-switching during RSL fall. Observations from the field and model runs provide a critical link in understanding the geomorphic processes occurring during RSL fall, and in particular show that 1) incision and sediment bypass is not a necessary response to RSL fall and 2) lateral migration of a delta via avulsion can continue to occur with falling sea-level. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Long-term perspectives on the evolution of river deltas have provided useful knowledge capable of responding to pending questions related to the ongoing climate and environmental changes. Increasing utilization pressure on delta environments has necessitated increased attention to protect the socio-economic and ecological values. As a result, multiple local initiatives have been designed, aimed at mitigating environmental deterioration and implementing adaptive measures, but many such initiatives have shown limited success. This thesis uses a case study of Save River delta in Mozambique to explore the relation between geomorphological evolution and socio-ecological system dynamics in delta environments. In addition, key environmental variables that concern the society today are highlighted and discussed in a management perspective. The results of the study show the development of Save River delta from the mid-Holocene to the present. The geomorphological settings of the delta suggest a faulted coastline over which subsequent deposition of fluvial sediments has formed a protruding delta front. Between c. 3000 and 1300 years ago, fine-grained sediments accumulated on top of the delta-front in the proximal part of the delta. This type of material was deposited under intertidal conditions and supported the formation of mangrove habitat. The geographical distribution of the mangrove deposit was driven by successive stages of back-barrier swamp formation and sea-level change as the delta evolved. From c. 1300 years ago, the river delta started to receive fluvial sediments from pulses of floods forming an alluvial floodplain. These sediments have accumulated mainly on the fine-grained mangrove wetland deposit. All the geomorphological features have evolved in a shoreward-shifting pattern over time. Centennial to decadal changes observed in the delta have followed a predictable geomorphological pattern, which is also part of the millennial evolution. The mangrove system, the base for the socio-economic system, is consequently strongly affected by the geomorphological development of the area. An increasing sensitivity of socio-ecological systems to environmental stressors, e.g. floods, cyclones and erosion, has motivated multiple initiatives to work towards a sustainable management of delta environments. This thesis highlights the need for interplay between geomorphology and ecology, considering both long- and short-term dynamics of delta environments. Hitherto, management initiatives have been concentrated on fragmented interventions of controlling water flow, which have disrupted the natural dynamics by obstructing the sedimentation-erosion cycle. To change this trend, coastal planners need to consider the significance of natural processes, e.g. cyclones, floods, erosion and accretion, for the long-term ecological and social sustainability of delta environments. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2. Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

Upper to lower delta plain fluvial sand bodies, sealed by delta plain mudstones, form important hydrocarbon reservoir targets. Modelling complex geobodies in the subsurface is challenging, with a significant degree of uncertainty on dimensions, distribution and connectivity. Studies of modern and ancient paralic systems have produced a myriad of nomenclature and hierarchy schemes for classifying fluvial architectural elements; often lacking clearly-defined terminology. These are largely based on outcrop data where lateral and vertical relationships of bounding scour surfaces can be assessed in detail. Many of these key defining criteria are difficult to recognise or cannot be obtained from typical 3D seismic reflection data at reservoir depths greater than or equal to 2 km subsurface. This research provides a detailed statistical analysis of the Triassic fluvio-deltaic Mungaroo Formation on the North West Shelf of Australia, which is one of the most important gas plays in the world. A multidisciplinary approach addresses the challenge of characterising the reservoir by utilising an integrated dataset of 830 m of conventional core, wireline logs from 21 wells (penetrating up to 1.4 km of the upper Mungaroo Fm) and a 3D seismic volume covering approximately 10,000 km2. Using seismic attribute analysis and frequency decomposition, constrained by well and core data, the planform geobody geometries and dimensions of a variety of architectural elements at different scales of observation are extracted. The results produce a statistically significant geobody database comprising over 27,000 measurements made from more than 6,000 sample points. Three classes of geobodies are identified and interpreted to represent fluvial channel belts and channel belt complexes of varying scales. Fluvial geobody dimensions and geomorphology vary spatially and temporally and the inferred controls on reservoir distribution and architecture are discussed. Results document periods of regression and transgression, interpreted in relation to potential allocyclic and autocyclic controls on the evolution of the depositional system. Statistical analysis of width-to-thickness dimensions and key metrics, such as sinuosity, provided a well-constrained and valuable dataset that augments, and has been compared to, existing published datasets. Uncertainty in interpretation caused by data resolution is addressed; something recognised in many other studies of paralic systems. Given the data distribution, type and resolution, geobodies have possible interpretations as either incised valleys or amalgamated channel belts, with implications for developing predictive models of the system. This study offers the first published, statistically significant dataset for the Mungaroo Formation. It builds upon previous regional work, offering a detailed analysis of this continental scale paralic system and provides insight into the controls and mechanisms that influenced its spatial and temporal evolution. Focusing on improved understanding of geobody distribution and origin, the statistical parameters generated provide a robust dataset that can be used for 3D static reservoir models of analogue systems. Thus, helping to constrain potential geobody dimensions and reduce the uncertainties associated with modelling.

Changes in external forcing having traditionally been the main area of interest in trying to understand paleo-depositional environments in sedimentary systems; however, autogenic variability has been rising in importance, while autogenic behavior has been thought of as a “noise” generator. Recently, autogenic variability has been rising in attention because decoupling allogenic signatures (externally driven) from the stratigraphic record requires robust understanding of autogenic variations (internally generated). This study aims to quantitatively measure autogenic processes under a range of flux conditions and to show that autogenic processes generate distinct signatures rather than random noise. We present data from a matrix of nine different tank experiments in order to systematically evaluate the effects of sediment flux and water discharge variations on the autogenic timescale of fluvial sediment storage and release processes and the implications of this data to the stratigraphic record. The sediment flux tow ater discharge ratio and the absolute values of these two discharges control the autogenic timescale. Variations in sediment supply yield two competing effects on the autogenic timescale. The primary sediment flux control causes a reduction in the autogenic timescale as an increase in sediment supply yields an increased rate of filling the “fluvial envelope” (the space between the maximum and minimum fluvial slopes obtained during storage and release events). In contrast, the secondary sediment flux control increases the size of the fluvial envelope and works against the primary sediment flux control. Increasing the water discharge increases the autogenic timescale by widening the fluvial envelope during the organization of the fluvial system and more importantly, diminishes the functionality of the secondary sediment control. A competition exists between these factors, causing a non-linear range of autogenic timescales for a given sediment flux to water discharge ratio. In the nine experiments here, as the ratio decreases, the secondary effects of variations in sediment supply are suppressed by the relatively high water discharge, and the timescale is more predictable using the primary sediment control. As the ratio increases, the secondary effects from sediment supply are enhanced by a poorly organized fluvial system, and the timescale converges to a narrow range. This suggests significant implications for autogenic sediment delivery and stratigraphic development in a wide range of discharge conditions in field cases. / text

A Bacia do Tucano Central, localizada no estado da Bahia, consiste em um meio-gráben alongado norte, cuja assimetria é gerada por uma falha de borda principal. O presente trabalho tem por objetivo a caracterização sedimentológica e estratigráfica detalhada dos depósitos deltaicos do Grupo Ilhas, acumulados durante a fase rifte. A partir de levantamentos de perfis colunares, elaboração de fotomosaicos e a análise de paleocorrentes, foram identificadas para o intervalo estudado doze litofácies, que podem ser agrupadas em quatro associações de fácies: prodelta, frente deltaica distal, frente deltaica proximal e planície deltaica. A partir do estudo do empilhamento estratigráfico dos afloramentos estudados, associados à análise de poços, foi possível determinar diferentes padrões de empilhamento. É possível dizer que a base do Grupo Ilhas apresenta padrão retrogradacional, indicando um trato de sistema tectônico de clímax de rifte. A porção superior, por sua vez, é caracterizada por um padrão progradacional, configurando o trato de sistemas tectônico de final de rifte. Através da interpretação do diagrama de paleocorrentes é possível identificar dois padrões distintos de alimentação fluvial dos deltas do Grupo Ilhas: um principal para S-SE, proveniente da borda axial, e outro secundário para E-SE, oriundo da borda flexural. A distribuição regional das paleocorrentes e o mapa de razão arenito/pelito sugerem um amplo meio-graben com depocentro a sul. / Depositional Model, Facies Architecture and Stratigraphic Evolution of the Deltaic Systems of Ilhas Group, Tucano Central Basin – BA. The Tucano Central Basin, located in the northeastern portion of the Bahia State, consists in an S-N elongated half-graben, which asymmetry is generated by a main border fault. The present work aims to a detailed sedimentological and stratigraphic characterization of the deltaic deposits of the Ilhas Group, accumulated during the rift phase. From sedimentary logs, preparation of photomosaics and paleocurrent analysis were identified twelve lithofacies, which can be grouped into four facies associations: pro-delta, distal deltaic front, proximal deltaic front and deltaic plain. Through the investigation of the stratigraphic succession of the studied outcrops associated with the analysis of wells, was possible to define distinctive stacking pattern. It is possible to consider that the base of the Ilhas Group presents a retrogradational pattern, indicating a rift climax tectonic system tract. The upper portion, on its turn, is characterized by a progradational pattern, configuring the rift ending tectonic system tract. By the interpretation of the paleocurrent diagram it’s possible to identify two distinct fluvial feeding patterns of the deltaic systems of the Ilhas Group: a main one with S-SE vector indication, which sediments are from axial border, and another one with E-SE vector indication, which sediments are from the flexural margin. The regional distribution of paleocurrent and the map of the sandstone/mudstone ration suggest a wide half graben basin with depocenter in the south part.

A Bacia do Tucano Central, localizada no estado da Bahia, consiste em um meio-gráben alongado norte, cuja assimetria é gerada por uma falha de borda principal. O presente trabalho tem por objetivo a caracterização sedimentológica e estratigráfica detalhada dos depósitos deltaicos do Grupo Ilhas, acumulados durante a fase rifte. A partir de levantamentos de perfis colunares, elaboração de fotomosaicos e a análise de paleocorrentes, foram identificadas para o intervalo estudado doze litofácies, que podem ser agrupadas em quatro associações de fácies: prodelta, frente deltaica distal, frente deltaica proximal e planície deltaica. A partir do estudo do empilhamento estratigráfico dos afloramentos estudados, associados à análise de poços, foi possível determinar diferentes padrões de empilhamento. É possível dizer que a base do Grupo Ilhas apresenta padrão retrogradacional, indicando um trato de sistema tectônico de clímax de rifte. A porção superior, por sua vez, é caracterizada por um padrão progradacional, configurando o trato de sistemas tectônico de final de rifte. Através da interpretação do diagrama de paleocorrentes é possível identificar dois padrões distintos de alimentação fluvial dos deltas do Grupo Ilhas: um principal para S-SE, proveniente da borda axial, e outro secundário para E-SE, oriundo da borda flexural. A distribuição regional das paleocorrentes e o mapa de razão arenito/pelito sugerem um amplo meio-graben com depocentro a sul. / Depositional Model, Facies Architecture and Stratigraphic Evolution of the Deltaic Systems of Ilhas Group, Tucano Central Basin – BA. The Tucano Central Basin, located in the northeastern portion of the Bahia State, consists in an S-N elongated half-graben, which asymmetry is generated by a main border fault. The present work aims to a detailed sedimentological and stratigraphic characterization of the deltaic deposits of the Ilhas Group, accumulated during the rift phase. From sedimentary logs, preparation of photomosaics and paleocurrent analysis were identified twelve lithofacies, which can be grouped into four facies associations: pro-delta, distal deltaic front, proximal deltaic front and deltaic plain. Through the investigation of the stratigraphic succession of the studied outcrops associated with the analysis of wells, was possible to define distinctive stacking pattern. It is possible to consider that the base of the Ilhas Group presents a retrogradational pattern, indicating a rift climax tectonic system tract. The upper portion, on its turn, is characterized by a progradational pattern, configuring the rift ending tectonic system tract. By the interpretation of the paleocurrent diagram it’s possible to identify two distinct fluvial feeding patterns of the deltaic systems of the Ilhas Group: a main one with S-SE vector indication, which sediments are from axial border, and another one with E-SE vector indication, which sediments are from the flexural margin. The regional distribution of paleocurrent and the map of the sandstone/mudstone ration suggest a wide half graben basin with depocenter in the south part.