Capture, Storage and Use of CO2 (CCUS). Seismic interpretation of existing 2D and 3D seismic data around the Havnsø structure (Part of work package 5 in the CCUS project)

Ulrik Gregersen, Henrik Vosgerau, Shahjahan Laghari, Kenneth Bredesen, Rasmus Rasmussen, Anders Mathiesen

Research output: Book/ReportReport (publicly available)

Abstract

This study presents a seismic stratigraphic interpretation and mapping of key horizons and faults of the Gassum Formation and Fjerritslev Formation in the Stenlille and Havnsø structures in the western Zealand and the Sejerø Bugt. The Havnsø structure is a large elongated, NW – SE trending four-way dip structural closure and the Stenlille structure is a smaller SW – NE trending four-way dip structural closure, at the top Gassum Formation (top reservoir) level and in the overlying Fjerritslev Formation (main seal). The top point of the Havnsø structure is located onshore near the coastline just south of Havnsø based on the currently available data. The saddle point of the structure is located approximately mid-way to the Stenlille structure. Both the Gassum and Fjerritslev formations are parts of these structures, which are mainly caused by underlying salt pillows and affected by minor SW – NE trending faulting. The Jurassic mid-Cimmerian regional tectonic phase probably contributed to the development of the structures with compressional tectonics and faulting. A detailed interpretation with well ties of formations and sequences is carried out in the Stenlille structure. In the Stenlille area, the Gassum Formation comprises mostly fluvial-deltaic, fluvial-estuarine, near-coastal and shallow marine sandstones, intercalated with lagoonal or offshore mudstone and heterolithic intervals. The formation is overlain by the mudstone-dominated Fjerritslev Formation. The sequences and seismic facies are attempted correlated towards the Havnsø structure, but due to very poor seismic data of low resolution a detailed interpretation and correlation is not possible. The challenge of correlation into the offshore part of the Havnsø structure into the Sejerø Bugt is furthermore complicated by dipping scanned seismic sections, which cause mis-ties along the sections. This is critical as this area is the northern part of the Havnsø structure, and as it will affect the interpreted horizons and thus the depth maps and closures (spill-point). Reprocessing was tested on selected lines and provided basis for regional correlation of formation boundaries, and a few sequence stratigraphic horizons (flooding surfaces) and faults. The general trend is that the Gassum Formation thickens westwards in the Havnsø structure area, but the sandstone-rich lower part of the formation in Stenlille (below the transgressive surface TS5) appears to have a relative constant thickness towards Havnsø with local thinning over the top of the structure. Especially for the upper part of the formation, it is possible that sandstone intervals become thinner and less in number on the behalf of thicker mudstone intervals due to a more offshore position in the Havnsø area compared to the Stenlille area at the time of deposition.
Original languageEnglish
Place of PublicationCopenhagen
PublisherGEUS
Number of pages60
Volume2020
DOIs
Publication statusPublished - 7 Dec 2020

Publication series

SeriesDanmarks og Grønlands Geologiske Undersøgelse Rapport
Number33
Volume2020

Keywords

  • Denmark

Programme Area

  • Programme Area 3: Energy Resources

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