The emplacement of igneous intrusions into sedimentary basins mechanically deforms the host rocks and causes hydrocarbon maturation. Existing models of host-rock deformation are investigated using high-quality 3D seismic and industry well data in the western Møre Basin offshore mid-Norway. The models include synemplacement (e.g., elastic bending-related active uplift and volume reduction of metamorphic aureoles) and postemplacement (e.g., differential compaction) mechanisms. We use the seismic interpretations of five horizons in the Cretaceous-Paleogene sequence (Springar, Tang, and Tare Formations) to analyze the host rock deformation induced by the emplacement of the underlying saucer-shaped Tulipan sill. The results show that the sill, emplaced between 55.8 and 54.9 Ma, is responsible for the overlying dome structure observed in the seismic data. Isochron maps of the deformed sediments, as well as deformation of the younger postemplacement sediments, document a good match between the spatial distribution of the dome and the periphery of the sill. The thickness t of the Tulipan is less than 100 m, whereas the amplitude f of the overlying dome ranges between 30 and 70 m. Spectral decomposition maps highlight the distribution of fractures in the upper part of the dome. These fractures are observed in between hydrothermal vent complexes in the outer parts of the dome structure. The 3D seismic horizon interpretation and volume rendering visualization of the Tulipan sill reveal fingers and an overall saucer-shaped geometry. We conclude that a combination of different mechanisms of overburden deformation, including (1) elastic bending, (2) shear failure, and (3) differential compaction, is responsible for the synemplacement formation and the postemplacement modification of the observed dome structure in the Tulipan area.
The mid-Norwegian margin is regarded as an example of a volcanic-rifted margin formed prior to and during the Paleogene breakup of the northeast Atlantic. The area is characterized by the presence of voluminous basaltic complexes such as extrusive lava and lava delta sequences, intrusive sills and dikes, and hydrothermal vent complexes. We have developed a detailed 3D seismic analysis of fluid-and gas-induced hydrothermal vent complexes in a 310 km 2 area in the Møre Basin, offshore Norway. We find that formation of hydrothermal vent complexes is accommodated by deformation of the host rock when sills are emplaced. Fluids are generated by metamorphic reactions and pore-fluid expansion around sills and are focused around sill tips due to buoyancy. Hydrothermal vent complexes are associated with doming of the overlying strata, leading to the formation of draping mounds above the vent contemporary surface. The morphological characteristics of the upper part and the underlying feeder structure (conduit zone) are imaged and studied in 3D seismic data. Well data indicate that the complexes formed during the early Eocene, linking their formation to the time of the Paleocene-Eocene thermal maximum at c. 56 Ma. The well data further suggest that the hydrothermal vent complexes were active for a considerable time period, corresponding to a c. 100 m thick transition zone unit with primary Apectodinium augustum and redeposited very mature Cretaceous and Jurassic palynomorphs. The newly derived understanding of age, structure, and formation of hydrothermal vent complexes in the Møre Basin contributes to the general understanding of the igneous plumbing system in volcanic basins and their implications for the paleoclimate and petroleum systems.
A new concept for DEOXYGENATION has been developed based on the use of an inert gas, which is recirculated; a specially designed stripping chamber and a catalyst bed. The concept has been fully proven in a prototype unit handling 500 m3/hour sea water. This unit is located on the Norwegian east coast and interested parties are welcome to inspect the installation. Long term development work will be carried out with this unit to assess its suitability for other applications and also to optimise mechanical and energy requirements. The prototype has demonstrated the considerable advantages now available, when compared with conventional vacuum and gas stripping units. Some of these advantages are particularly attractive for offshore operators viz:Substantial savings of space and weight.Very low levels of residual dissolved oxygen.The need for chemical scavengers can be eliminated.No large volumes of stripping gas requiring flaring - a major advantage over conventional gas stripping.Units will operate with unfiltered sea water without a build up of foulants.Units can be sited in platform legs thus saving deck space.Modular construction provides flexibility in performance. The process comprises a stripping chamber in which nitrogen is used to remove dissolved oxygen from the liquid phase. Separated "gas" is thenpassed over a catalyst bed in the presence of a "reactant". Oxygen free gas is then returned to the stripping chamber for re-use. Details of the process, laboratory studies and prototype operations are presented in this paper. Introduction. Sea water injection is widely used for enhanced oil recovery in offshore fields. Removal of dissolved oxygen from sea water reduces the incidence of corrosion "pitting" of unprotected carbon steel equipment. The elimination of corrosion is necessary to avoid "fouling" of flow lines or a build up of deposits at the well-bore face. Current practice is to deoxygenate with large, packed towers, operating either under vacuum, or with natural gas as a stripping medium. Such systems can reduce dissolved oxygen to very low levels, particularly gas stripping units, but the ratio of gas to water volume is very high and many governments have restricted the volume of gas which can be flared during normal operations. Conventional units must therefore be regarded as a compromise in terms of:SIZEWEIGHTCONFIGURATION (location)PROCESS RESTRICTIONS andPERFORMANCE Residual dissolved oxygen levels of 50 to 100 ppb are obtained without theaddition of chemical scavenger. Further reduction to less than 5 ppb O2 is achieved by the addition of a solution of either ammonium hydrogen sulphite or sodium hydrogen sulphite. Large sea water injection systems consume substantial quantities of chemical oxygen scavenger. Such chemicals are not expensive in themselves but the logistics should be considered since bulk storage is often required both onshore and offshore, expensive travel tanks are required to satisfy IMCO standards (class I).
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