The impact of salt tectonics on the Mesozoic sedimentation and petroleum systems of the Norwegian Barents Sea
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- PhD theses (TN-IER) 
Original versionThe impact of salt tectonics on the Mesozoic sedimentation and petroleum systems of the Norwegian Barents Sea by Luis Alberto Rojo Moraleda. Stavanger : University of Stavanger, 2020 (PhD thesis UiS, no. 540)
In the Norwegian Barents Sea, Mesozoic and Cenozoic mobilization of Pennsylvanian-lower Permian layered evaporite sequences (LES) resulted in areas with salt tectonics (e.g. Nordkapp, Tromsø and Tiddlybanken basins), which affected the development of Upper Paleozoic and Mesozoic petroleum systems. Over the last three decades, seismic imaging in these salt-bearing basins has been a challenge due to the presence of closely spaced salt diapirs and steep minibasin strata. Consequently, there is limited information and integrated studies, and the dynamics of salt mobilization and its effect on the petroleum systems remain poorly understood. This research applies a wide range of methods to subsurface data in the Nordkapp and Tiddlybanken basins to: (1) provide a tectonostratigraphic evolution of the basins; (2) understand the influence of salt movement on Mesozoic prograding overburdens; and (3) address the thermal effect of salt in the petroleum systems of the Barents Sea. The results are presented in five papers. Paper I improves the understanding of salt tectonics in the Nordkapp Basin based on interpretation of subsurface data and structural restorations. Our results indicate that a combination of Early Triassic basement-involved extension and sediment progradation resulted in diachronous salt mobilization and sediment infill along the basin. Important processes such as diapirism, minibasins formation, welding, and salt depletion occurred earlier in the central and eastern sub-basins than in the western sub-basin. The paper also highlights the importance of salt rheology and subsalt relief for the nucleation and distribution of salt structures and minibasins. Paper II aims to understand the controls on suprasalt structural style in confined salt-bearing basins based on analogue experiments. The paper compares the structural styles resulting from basement involved extension and progradational loading. Moreover, it highlights the impact of subsalt relief on suprasalt deformation by comparing different subsalt basin configurations. Finally, the models are upscaled and compared to seismic sections through the Nordkapp Basin to illustrate the influence of these processes on the evolution and structural style of the basin. Paper III combines subsurface data, 3D structural restorations and forward stratigraphic modelling in the Tiddlybanken Basin to understand the influence of salt tectonics on Mesozoic prograding overburdens. The paper illustrates how salt mobilization causes drastic vertical and lateral changes in relative sea level, which in turn induce lateral variations in clinoform geometry and progradation rates. These variations result in complex spatial and temporal stacking patterns in salt minibasins. Moreover, this study emphasises the importance of forward stratigraphic modelling in the study of tectonically active areas such as salt bearing basins, since the isolated use of conventional methodologies might lead to potential pitfalls with negative consequences for exploration models. Paper IV combines subsurface data and minibasin/prospect-scale restorations to describe near-diapir deformation and minibasin subsidence in the Nordkapp Basin. Diapir growth resulted in different scales of drape folding such as megaflaps, minibasin-scale folding, and composite halokinetic sequences, which could work as structural traps. Salt growth also produced sediment erosion and reworking of the Triassic overburden, which explains the deposition of peridiapiric wedges at diapir flanks. This paper also illustrates the role of minibasin subsidence on the temporal and spatial distribution of Triassic depositional environments, where salt withdrawal caused the retrogradation of Triassic fluviodeltaic systems and favoured local embayments with deposition of source rocks. Paper V combines structural restorations from paper I and thermal modelling to show the impact of salt tectonics on the thermal evolution and petroleum system of confined salt-bearing basins such as the Nordkapp Basin, commonly characterized by narrow minibasins and closely-spaced diapirs. The results indicate that thermal anomalies associated to closely-spaced diapirs mutually interfere and induce a combined anomaly that reduces the overall temperature in the basin. The presence of isolated diapirs also reduce the temperature in adjacent minibasins. However, this effect is laterally limited and depends on the shape and width of the diapir. Finally, the paper emphasises the importance of integrating structural restorations and thermal modelling in confined salt-bearing basins since the thermal effect of evolving salt structures can unlock new exploration concepts such as deep hydrocarbon kitchens and reservoirs. This PhD thesis has implications for the understanding of salt tectonics, minibasin infill, and the petroleum system of confined salt-bearing basins in the Norwegian Barents Sea. Furthermore, the results contribute to the understanding of these processes in similar basins worldwide.
Has partsPaper 1: Rojo, L.A., Cardozon, N., Escalona, A., Koyi, H. (2019) Structural style and evolution of the Nordkapp Basin, Norwegian Barents Sea. AAPG Bulletin, 103(9), pp. 2177-2217, DOI:10.1306/01301918028). This paper is not in Brage for copyright reasons.
Paper 2: Paper 2: Rojo, L.A., Koyi, H., Cardozo, N., Escalona, A. (2020) Controls on suprasalt deformation in confined salt-bearing basins: insights from analogue modelling. Submitted to the Journal of Structural Geology.
Paper 3: Rojo, L.A., Marin, D., Cardozo, N. et al. (2019) The influence of halokinesis on prograding clinoforms: Insights from the Tiddlybanken Basin, Norwegian Barents Sea. Basin Research, DOI: 10.1111/bre.12411
Paper 4: Rojo, L.A., Escalona, A. (2018) Controls on minibasin infill in the Nordkapp Basin: Evidence of complex Triassic synsedimentary deposition influenced by salt tectonics. AAPG Bulletin, 102(7), pp. 1239-1272, DOI: 10.1111/bre.12411. This paper is not available in Brage for copyright reasons.
Paper 5: Cedeño, A., Rojo, L.A., Cardozo, N. et al. (2019) The impact of salt tectonics on the thermal evolution and petroleum systems of confined rift basins: Insights from basin modelling of the Nordkapp Basin, Norwegian Barents Sea, vol. 9, DOI: 10.3390/geosciences9070316