The Campos Basin, located on the southeastern Brazil passive margin, is one of the most productive basins in the western South Atlantic. The development of many siliciclastic turbidite reservoirs in the southeastern Brazilian margin provided a great interest in submarine channel systems of the Campos Basin for hydrocarbon exploration purposes. Prior research highlights the variation of sediment supply, sea-level fluctuations and tectonic activity as the most critical controls on channel development within the Campos Basin. The Campos Basin is structurally complex as a result of salt movement, and it is an ideal setting in which to investigate the influences of structural deformation on channel evolution and architecture. I investigated the interaction between development of a post-Miocene submarine channel system and structural deformation related to salt tectonics by using structural and stratigraphic analysis of 3D seismic-reflection data, which covers an area of approximately 1750 km2. I produced detailed maps and cross sections of the submarine channel system, and compared them to structural maps in order to interpret the control of structural deformation on evolution and architecture of the submarine channel system. I interpreted that a regionally mapped seismic-reflection horizon approximates the paleobathymetry at the time of channel formation and correlated with the trend of the channel system. The paleobathymetry mainly dictated the transport pathway of the submarine channel system, as channels within the system mainly stayed in salt-withdrawal basins and avoided salt-influenced structural highs. However, the submarine channel system was diverted to flow directly on the top of a salt diapir within the southeastern part of the study area, rather than staying within salt-withdrawal basins. I explained this anomaly by two uplift stages of the salt diapir. Aggradation smoothed out much of the paleobathymetry associated with the first growth stage of the salt diapir, and the salt-influenced structural high was not able to divert the submarine channel system. The basal surfaces of channels within the system are deformed as a result of the growth of the salt diapir, which suggests that the salt diapir became active again when the submarine channel system started to develop.
The dissertation examines the interaction between basement tectonics, salt tectonics and sedimentation during the Late Cretaceous basement reactivation in the center of the Santos Basin. The study area is a seismic volume 60 x 30 km2 in area, augmented by 2D regional seismic lines. The results of seismic interpretation and structural restorations revealed important inversions in the Late Cretaceous, including inversion of an NNE-oriented aborted rift segment known as Merluza Graben. The following tectono-stratigraphic evolution was inferred. During the Albian, basin subsidence and differential loading by the overburden caused salt to flow basinwards. In the Late Turonian, intraplate compression resulted in uplift of the onshore and proximal areas of the Santos Basin and in a newly recognized basement inversion in deep water. ENE and NNE oriented structures were reactivated. The uplift exposed the Turonian shelf and a new shelf began to prograde. The first shelves were narrow (~25 km wide) but enlarged to 60 km in the Santonian. Salt influenced the position of the shelf break and the progradation pattern of the shelf margin. Because of the continuous accommodation space provided by salt withdrawal underneath the sedimentary wedge, the shelf margin aggraded until underlying salt welded, after which the shelf prograded to a position around 50 km to the east of the present-day shelf break. Deformation peaked in the Late Santonian when the shelf was widest, the rate of progradation of the shelf margin was anomalously high, and transtension along the borders of the Merluza Graben allowed Late Santonian magma to intrude. Salt acted as a partial seal, causing a large part of the magma to spread beneath it. Some magma formed sills inside the evaporitic layer, intruding zones of dilation in the salt. Magma also followed the top of the evaporitic layer and intruded salt-related faults as dikes. These dikes supplied sills in the overburden and extrusive flows emerged on the Late Santonian seafloor from ENE-striking transtensional zones. Right-lateral reactivation of the Merluza Graben borders slightly compressed the graben, which favored sill injection in Coniacian/Santonian strata. Tectonic activity diminished towards the end of the Cretaceous.
Salt tectonics is the study of how and why salt structures evolve and the three-dimensional forms that result. A fascinating branch of geology in itself, salt tectonics is also vitally important to the petroleum industry. Covering the entire scale from the microscopic to the continental, this textbook is an unrivalled consolidation of all topics related to salt tectonics: evaporite deposition and flow, salt structures, salt systems, and practical applications. Coverage of the principles of salt tectonics is supported by more than 600 color illustrations, including 200 seismic images captured by state-of-the-art geophysical techniques and tectonic models from the Applied Geodynamics Laboratory at the University of Texas, Austin. These combine to provide a cohesive and wide-ranging insight into this extremely visual subject. This is the definitive practical handbook for professional geologists and geophysicists in the petroleum industry, an invaluable textbook for graduate students, and a reference textbook for researchers in various geoscience fields.
In this timely volume, geoscientists from both industry and academia present a contemporary view of salt at a global scale. The studies examine the influence of salt on synkinematic sedimentation, its role in basin evolution and tectonics, and ultimately in hydrocarbon prospectivity. Recent improvements in seismic reflection, acquisition and processing techniques have led to significant advances in the understanding of salt and sediment interactions, both along the flanks of vertical or overturned salt margins, and in subsalt plays such as offshore Brazil. The book is broadly separated into five major themes covering a variety of geographical and process-linked topics. These are: halokinetic sequence stratigraphy, salt in passive margin settings, Central European salt basins, deformation within and adjacent to salt, and salt in contractional settings and salt glaciers.
The Northern Gulf of Mexico Basin is part of an ocean basin characterized by a complex structural framework. The complex structural framework is shaped by the dynamic interaction between salt tectonics and sedimentation. Salt withdrawal mini-basins are among the structural features produced by this interaction and are of particular interest to hydrocarbon exploration. The mini-basins provide significant accommodation in which thick packages of sediments can accumulate. The accumulation of sediments can be very rapid during episodes of high sedimentation, such as occurred in the middle Miocene episodes in the northeastern Gulf of Mexico. Rapid accumulation of sediment in turn changes the local topography of the mini-basin and also leads to significant buildup of overpressure. In such settings, the structure and stratigraphy in the vicinity of a mini-basin are influenced by salt movement. Moreover, the rock properties can be altered due to salt movement and overpressure development. Therefore, the factors of salt movement and overpressure development are crucial in understanding the evolution of the petroleum system in mini-basins. Insights on the roles of these factors in defining the evolution of the petroleum system are beneficial for hydrocarbon exploration. Such insights are of use in addressing practical problems in reservoir characterization, pore pressure prediction, and basin and petroleum system modeling (BPSM). This dissertation establishes insights on the roles of these factors through meticulous quantification of related geologic processes to address some of the stated practical problems above. Chapter 1 quantifies the spatial variations in sediment compaction and clay diagenesis to define spatial trends of elastic properties, which are used for seismic reservoir characterization. We demonstrate the advantages of using this integrated method in a frontier area. Chapter 2 studies the impact of high sedimentation and salt movement on the thermal history of a mini-basin to propose a workflow for predicting the effects of smectite to illite diagenesis on overpressure. Chapter 3 investigates the implications of lateral slip along salt-related faults to pressure and thermal history to address the proper application of BPSM techniques in constructing paleo-geometry when modeling these faults. All three chapters of this dissertation focus on the Thunder Horse mini-basin in the Mississippi Canyon area by integrating 3D seismic data with well logs, biostratigraphic data, and borehole measurements of pore pressure and temperature. Chapter 1 evaluates spatial changes in effective stress and smectite to illite diagenesis across Thunder Horse mini-basin using a 2D basin model that accounts for salt movement and properly calibrated with a single well. The results from the 2D model indicate that the central part of the mini-basin known as Thunder Horse field is associated with higher effective stress and shallower zone of smectite to illite transformation than the northwestern part known as Thunder Horse North field. Proper rock physics models are subsequently built to link the basin modeling results to seismic impedances and use them for quantitative seismic interpretation with spatially limited well control. The rock physics models are designed to account for the effects of sediment compaction and smectite to illite diagenesis on seismic impedances. The results from the quantitative seismic interpretation with a single well and basin modeling extrapolations of seismic impedance (extrapolation workflow) are comparable in their quality with those results obtained through the quantitative seismic interpretation with multiple wells scattered across the area (reference workflow). The training data sets of the seismic impedances of lithofacies corresponding to both of these workflows are similar in terms of the distribution of values and the pronounced spatial trends. In addition, the seismic inversion results of both of them are similar in terms of the quality of inverted impedances. Ultimately, these two workflows are close to each other in estimating the net pay volume of the reservoir and show the same degree of uncertainty in mapping reservoir lithofacies. This chapter was published first in AAPG Bulletin in May, 2017 'Ahead of Print' and officially appeared in the April, 2018 Bulletin. The publication focused on showcasing the workflow of combining basin modeling with seismic reservoir characterization. A refined version of this workflow that rigorously addresses spatial variability of training data of seismic impedances of lithofacies and uncertainty was accepted for publication in Geophysics in March, 2018. Both publications are co-authored with Tapan Mukerji, Allegra Hosford Scheirer and Stephan A. Graham. Dr. Tapan Mukerji contributed to the conception and design of the study. Dr. Allegra Hosford Scheirer provided guidance on building the basin model. Dr. Stephan A. Graham provided guidance on relating seismic impedances to geologic processes in the subsurface. Chapter 2 simulates thermal history of the mini-basin to quantify the impact of high sedimentation and salt movement. Then, the chapter integrates the modeled thermal history with rock physics models to predict the generation of overpressure due to smectite to illite diagenesis. A time-dependent solution of thermal history, simulated with a 2D basin model across Thunder Horse mini-basin, shows calibration to corrected bottom hole temperatures and illitic content of XRD data when combined with the proper kinetics. The time-dependent solution indicates fluctuations of the high heat flux by the middle Miocene due to high sedimentation. In addition, the solution suggests mitigation of the transient effects of high sedimentation by the high conductivity of the extruded salt sheet that completely covers Thunder Horse North field. Comparing the time-dependent solution with a steady state solution, the steady state solution overestimates temperature and illitic content through time and the differences between the two solutions are more significant in Thunder Horse field. After building rock physics models that account for thermal history to define a relationship between effective stress and both P-wave velocity and density on the basis of illite content, the rock physics models show a predictive power of pore pressure that is sensitive to the incorporated solution of thermal history. On one hand, incorporating a solution of thermal history that addresses the geologic factors of high sedimentation and salt movement (i.e., time-dependent solution) yields accurate prediction of pore pressure from seismic P-wave velocity based on the rock physics models. On the other hand, oversimplification of the solution of thermal history with a steady state solution leads to inaccurate estimation of pore pressure by the rock physics models. Therefore, addressing the geologic factors controlling the thermal history is essential to accurately predict pore pressure from seismic velocity using rock physics. This chapter is submitted into Marine and Petroleum Geology and co-authored with Tapan Mukerji, Nader C. Dutta and Allegra Hosford Scheirer. Dr. Tapan Mukerji contributed to the design of the study, rock physics modeling, pore pressure prediction, and thermal history modeling. Dr. Nader C. Dutta advised on the design of the study and the rock physics modeling and pore pressure prediction. Dr. Allegra Hosford Scheirer guided on constructing the basin model. Chapter 3 compares the techniques for constructing paleo-geometry in BPSM (i.e., pure porosity controlled backstripping vs imposing structural restorations on paleo-geometry) in terms of the simulated pore pressure and thermal history across a salt related structure of lateral slip. This chapter focuses on an expulsion rollover fault to the northeast of Thunder Horse mini-basin (i.e., listric fault that soles in a salt decollement). The two techniques of constructing paleo-geometry differ exclusively in the thickness of stratigraphic layers and stratigraphic contacts with salt through geologic time. These differences in paleo-geometry cause differences in the simulated pore pressure and thermal history. The technique of imposing structural restorations on paleo-geometry results in higher pore pressure build up over time and higher temperatures earlier in the history of the mini-basin when compared to the technique of porosity-controlled backstripping. These differences between the two techniques are spatially concentrated in the vicinity of the expulsion rollover fault. Therefore, the lateral slip impacts pressure and thermal history across the structure and the spatial extent of this impact depends on the amount of lateral slip. This chapter is submitted to Basin Research and co-authored with Kristian E. Meisling, Tapan Mukerji and Allegra Hosford Scheirer. Dr. Kristian E. Meisling provided guidance on seismic interpretation across the salt structures and on the sequential structural restoration. Dr. Tapan Mukeri helped with the initial design of the study and with some of the interpretations of the basin models. Dr. Allegra Hosford Scheirer helped with some of the interpretations of the basin models.
The Orpheus rift basin is part of the eastern North American rift system that formed prior to the opening of Atlantic Ocean. Using 2D seismic-reflection and well data and with information from the adjacent Fundy rift basin, I have defined the styles of deformation that formed during the development of the Orpheus rift basin. The basin geometry influenced deformation style by controlling the initial thickness of the massive lower Argo salt. Generally, the lower Argo salt is thin or absent above shallow fault blocks and thick above deep fault blocks. The composition of the upper Argo Formation, which consists of halite and interbedded clastic sedimentary rocks, also influenced the deformation style in the basin. In parts of the basin, the halite of the upper Argo Formation is interbedded with numerous, thick shale beds. In other parts of the basin, however, the upper Argo Formation is predominantly halite with few shale beds, allowing it to behave ductilely like the massive lower Argo salt. The synrift Argo salt significantly influenced deformation during and after rifting. Growth beds in the upper Argo Formation associated with extensional fault-propagation folds reflect continued activity on basement-involved faults below the salt during its deposition. During the later phases of rifting, paired minibasins and salt walls/columns preferentially formed where the lower Argo salt was thick and/or where the upper Argo Formation had a high proportion of halite. Sediment loading near the northern border faults caused the underlying salt to move laterally, forming the minibasins, salt walls/columns, and possibly detached compressional structures. Immediately after rifting, shortening associated with basin inversion reactivated some basement-involved faults. Detached compressional structures (i.e., salt-cored folds) located to the south and far from minibasins likely resulted from this basement-involved shortening. It is unclear whether the detached compressional structures near the minibasins formed, at least in part, in response to the basement-involved shortening. The nature of the widespread unconformity during the Late Jurassic/Early Cretaceous remains unclear. However, additional postrift deformation during the Oligocene/Miocene again reactivated some basement-involved faults and shortened the buried salt walls/columns, producing domes in the sedimentary cover above them.
