Compaction, Rock properties evaluation, Rock physics diagnostics, AVO modeling and seismic inversion in the Snøhvit field, SW Barents Sea
Snøhvit field is located in the SW Barents Sea and comprises a reservoir in Lower to Middle Jurassic sandstones of Stø Formation containing gas with thin oil lag. The sandstones of Upper Triassic to Lower Jurassic Nordmela and Tubåen Formations have also shown gas in few wells. Several stages of upl...
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| Format: | Master Thesis |
| Language: | English |
| Published: |
2012
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| Online Access: | http://hdl.handle.net/10852/12563 http://urn.nb.no/URN:NBN:no-31757 |
| Summary: | Snøhvit field is located in the SW Barents Sea and comprises a reservoir in Lower to Middle Jurassic sandstones of Stø Formation containing gas with thin oil lag. The sandstones of Upper Triassic to Lower Jurassic Nordmela and Tubåen Formations have also shown gas in few wells. Several stages of uplift and erosion of the entire region resulted in dramatic changes in reservoir rock properties and petroleum system. Hence, analysis of this sedimentary basin as a normally subsiding basin would mislead the exploration results. An integrated approach that incorporates compaction analysis, rock physics diagnostics, AVO modeling and post-stack seismic inversion has been carried out to predict reservoir properties of the Snøhvit field. Six exploration wells drilled in the study area and three 2D seismic lines have been considered for detail compaction, AVO modeling inversion and detail rock physics analyses. Naturally compacted rocks in the well 7121/5-1 indicate transformation in compaction domain (MC to CC) at present depth 1922 m (BSF) corresponding to present day temperature of 66⁰C. An abrupt velocity increase at this depth is inferred as a result of grain framework stiffening related to precipitation of micro-quartz cement. The higher velocity-depth gradient of this sediment than laboratory experimental curves is related to the burial history and subsequent uplift. However, the estimated exhumation in the studied area varies between 300 and 760 m. The present day temperature of well 7121/5-1 at transition depth after exhumation is 93⁰C which is quite enough to change the rock stiffness. But, the present day temperature (50⁰C) at transition depth in well 7120/5-1 indicates the paleo-temperature history in this basin was different. The velocity of the Stø Formation in the eastern well is lower than the western well. The eastern well is located more close to the shore line which may control deposition of coarse and well sorted sediments. Hence, the influence of compaction (both mechanical and chemical) is lower in the ... |
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