[1] We use 2-D thermomechanical models to investigate the early evolution of rifted margin salt tectonics in terms of the competition among margin tilt, salt flow, and sediment aggradation. Model experiments include initial geometry of the rifted margin and autochthonous salt basin, subsequent synrift and thermal subsidence, sediment and water loading, and sediment compaction. We also calculate the thermal evolution of the system to investigate the impact of the high thermal conductivity of the salt (halite). Model Set 1 demonstrates a two-phase response to salt deposition: short-term thermal equilibration between the salt and crust and longer-term relaxation in which the salt basin thermal image penetrates to a depth on the order of its width. Set 2 addresses the competition among margin tilt, salt flow, and sediment aggradation. Set 3 examines other factors, the salt basin width and depth, and the rifted margin width, which potentially affect the system evolution. Set 4 shows that sawtooth subsalt topography, representing faulted basement grabens, does not strongly impede salt flow. The model results are discussed in terms of a ternary diagram with apices representing tilt, salt flow, and sedimentation rates. Characteristic styles include the following: (1) tilt and rapid salt flow draining salt to the distal basin before the sediment aggrades, (2) an equivalent system with faster aggradation that captures draining salt as diapirs between minibasins, and (3) rapid sediment aggradation in which diapir-minibasins systems develop before the salt drains. Thermal consequences of these styles are discussed. A preliminary comparison shows that salt structures resembling these styles occur in the southwest Nova Scotian margin.
Geologic carbon storage (GCS) is a fundamental pillar of carbon management that helps mitigate greenhouse gas emissions and addresses the negative effects of climate change. Viable CO2 storage sites share some of the same elements required for successful petroleum systems. For example, while reservoir, seal, and trap are required, migration pathway and timing are not important for CO2 storage, because rather than withdrawing fluid from a trap, CO2 storage involves injection into a geologic trap. Conceptually, this represents a form of reverse production. Numerous petroleum traps around the world, as well as naturally occurring CO2-producing fields and natural gas storage sites attest that safe, long-term storage is possible. Research over the past two decades identified five methods of Geologic Carbon Storage which have been validated through several demonstration and pilot projects around the world: (1) storage in depleted oil and gas fields, (2) use of CO2 in enhanced hydrocarbons recovery (3) storage in saline formations/aquifers, (4) injection into deep unmineable coal seams, and (5) in-situ/ex-situ carbon mineralization. The greatest volumetric potential for GCS is found in saline aquifers which are present throughout the world’s sedimentary basins.
In this paper, we present results from the first-ever 3D geomechanical model that supports pre-drill prediction of regional in-situ stresses throughout the Arabian Plate. The results can be used in various applications in the petroleum industry such as fault slip-tendency analysis, hydraulic fracture stimulation design, wellbore stability analysis and underground carbon storage. The Arabian tectonic plate originated by rifting of NE Africa to form the Red Sea and the Gulfs of Aden and Aqaba. The continental rifting was followed by the formation of collisional zones with eastern Turkey, Eurasia and the Indo-Australian Plate, which resulted in the formation of the Eastern Anatolian fault system, the fold-thrust belts of Zagros and Makran, and the Owen fracture zone. This present-day plate tectonic framework, and the ongoing movement of the Arabian continental lithosphere, exert a first-order control on the of in-situ stresses within its sedimentary basins. Using data from published studies, we developed a 3D finite element of the Arabian lithospheric plate that takes into account interaction between the complex 3D plate geometry and present-day plate boundary velocities, on elastic stress accumulation in the Arabian crust. The model geometry captures the first-order topographic features of the Arabian plate such as the Arabian shield, the Zagros Mountains and sedimentary thickness variations throughout the tectonic plate. The model results provide useful insights into the variations in in-situ stresses in sediments and crystalline basement throughout Arabia. The interaction between forces from different plate boundaries results in a complex transitional stress state (thrust/strike-slip or normal/strike-slip) in the interior regions of the plate such that the regional tectonic stress regime at any point may not be reconciled directly with the anticipated Andersonian stress regimes at the closest plate boundary. In the sedimentary basin east of the Arabian shield, the azimuths of the maximum principal compressive stresses change from ENE in southeast to ~N-S in northern portions of the plate. The shape of the plate boundary, particularly along the collisional boundaries, plays a prominent in controlling both the magnitude and orientations of the principal stresses. In addition, the geometry of the Arabian shield in western KSA and variations in the sedimentary basin thickness, cause significant local stress perturbations over 10 – 100 km length scales in different regions of the plate. The model results can provide quantitative constraints on relative magnitudes of principal stresses and horizontal stress anisotropy, both of which are critical inputs for various subsurface applications such as mechanical earth model (MEM) and subsequently wellbore stability analysis (WSA). The calibrated model results can potentially reduce uncertainties in input stress parameters for MEM and WSA and offer improvements over traditional in-situ stress estimation techniques.
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