Loading Events

« All Events

  • This event has passed.

Umut Isikalp

June 12, 2024 @ 12:15 pm - 1:00 pm

4D Evolution of a Salt Wall and Implication for Flanking Minibasin Stratigraphy: An Example from the Egersund Basin, Norwegian North Sea

Umut Isikalp

Salt diapirs are the most common type of salt-tectonic structure, occurring in many, if not all, salt basins. Two main types of diapiric structures are typically developed: salt walls, which are defined by axial ratios >2, and salt stocks, which have axial ratios <2. Diapirs form in response to a range of geological processes, including contraction, extension, differential loading, and buoyancy instabilities. Differential loading is often associated with the formation of minibasins, which subside and subsequently drive salt into adjacent diapirs. Although we have a good general understanding of the growth of diapirs, our knowledge of their four-dimensional evolution and the temporal and spatial relationships between walls and stocks is relatively limited.
In this study, we examine Triassic stratal geometries around a 23 km long, 2.5 km wide and 3100 ms (TWT) tall salt wall in the Egersund Basin, offshore Norway. In particular, we explore how stratal geometries develop in 4-D and how they are influenced by evolving salt structure and other controls in a continental depositional environment. The Egersund Basin and the salt wall we have chosen are an ideal study location, given it contains seismically well-imaged salt structures and adjacent minibasins. Well 17-12-1R penetrates the entire thickness of the Triassic minibasin succession, allowing us to construct a robust, age-constrained seismic-stratigraphic framework, and to analyse diapir kinematics in 4-D. 
We identify and map six Triassic sequences and undertake schematic restorations of Triassic stratal geometries on both wall-perpendicular and wall-parallel (through axes of flanking minibasins) seismic sections. Analysis of thickness patterns and salt-sediment relationships on wall-perpendicular sections suggests the initial trigger for salt mobilization into the wall was sediment loading. This loading led to the formation of a pillow, which, during the early Carnian period, evolved diachronously into a wall due to the varying timing of erosion of the overburden and active diapirism. Thickness patterns, stratal upturns, the style, and distribution of angular unconformities between seismic sequences, and variations in axial fold traces suggest the driving force of wall growth from the mid-Carnian to the end of the Triassic was passive diapirism (i.e., sediment loading), which was associated with minibasin downbuilding. Wall-parallel seismic sections within the axes of flanking minibasins indicate that superimposed on this general growth pattern was the formation of along-strike turtle structures, pointing the growth of salt welds during both the Carnian and Norian periods, related to complex, four-dimensional salt flow into nearby diapirs.
The complex spatio-temporal variations in subsidence, stratal upturns, angular unconformities, thickening, and thinning patterns around the salt wall over time, driven by salt flow and diapir evolution, have significant implications for the geometry and distribution of potential reservoirs, relevant for both carbon capture and storage as well as traditional oil and gas exploration.

Details

Date:
June 12, 2024
Time:
12:15 pm - 1:00 pm

Venue

Kontinentalsokkelen (2G16e)
Realfagbygget, Allégaten 41
Bergen, 5007 Norway
+ Google Map