On 26th March 1993, the discovery well 15/9-19 SR was up for completion and production testing. The
Image 1: Location of the 15/9-19 SR well and the Theta Vest Structure
A drill stem test had been carried out between the interval, 2863.6 – 2880.5 m TVD MSL. The permeability estimated from the build-up analyses was approximately 914
The distribution of the block ownerships:
Statoil (operator) | 52.6% |
Esso | 28.0% |
Norsk Hydro | 9.4% |
Elf | 9.0% |
Total | 1.0% |
The primary objective of the well was to test the hydrocarbon potential in the Heimdal Formation of Paleocene age, which is the main reservoir in the Sleipner Øst area while the secondary objective was to test the hydrocarbon potential in sandstones of Jurassic/Triassic age. However, the secondary objective led to the fortuitous encounter of oil in the Middle Jurassic Hugin Formation (Image 2).
Image 2: Structural cross-section along the 15/9-19 SR well path
The 18
The Theta Vest structure and the oil trap is a dome-shaped structure. This trap has a well-defined spill point to the east and is, best case, believed to be filled down to this point. However, several faults cutting the crest of the structure are thought to be sealing off, the hydrocarbon accumulation, from spilling eastwards.
The core logging, covering the lower part of the Middle Jurassic Hugin Formation and the uppermost part of the Triassic Skagerrak Formation, indicates a high frequency of fractures in the cores. This suggests the penetration of a zone of intense and complex faulting. The application of a pure or simple shear model gives an unfaulted thickness in the range of 24 to 27 meters. (Explained in the next blog).
The petrophysical analysis of the Hugin Formation in the 15/9-19 SR well results in a mean net/gross of 0.924, porosity of 22.6%, permeability of 2913.2
The most probable resource estimate for the Hugin reservoir in the Theta Vest structure is 10.33×106 Sm3 oil in place and 1.65×109 Sm3 associated gas phase in place. A recovery factor of 45%, leaves us with 4.55×106 Sm3 of recoverable oil and 0.72×109 Sm3 of recoverable associated gas phase.
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