The Heidrun Field, Offshore Mid-Norway
James S. Jackson1, Thomas Arthur2, Robert C. Olson3, and Dennis B. Tower4
1 Portland State University, Portland, OR
2 Consultant, Slough, Berkshire, United Kingdom
3 Consultant, New Castle, United Kingdom
4 Consultant, Sisters, OR
The Heidrun Field was discovered in 1985 by well 6507/7-2. Reserves are 175 million cubic meters oil and 40.7 billion cubic meters gas. Production commenced in 1995.
The NPD offered block 6507/7 in the Eighth License Round, after three oil and gas fields were discovered on the Mid-Norway shelf.
The petroleum system was understood to include Lower and Upper Jurassic source rock intervals. Thick delta and shelf sandstones overlain by transgressive claystones formed laterally extensive reservoir-seal couplets within the Jurassic interval. Faulting during the Jurassic and early Cretaceous created large traps that were imaged on a 2 x2 km 2D grid of seismic data.
Well 6507/10-1 was drilled in 1982 on a location down dip of the later Heidrun discovery. The well encountered water bearing Jurassic sandstones. Traces of oil recovered from cores were interpreted by the operator not to represent migrated hydrocarbons. The operator concluded that faulting near the crest of the structure failed to create a viable trap.
ARCO Norway acquired a suite of seismic lines over the crest of the structure for use in the 8th Round evaluation. The lines were interpreted to demonstrate a valid trap on block 6507/7 up dip of well 6507/10-1. This was confirmed by the discovery well and the subsequent development program.
The Heidrun field demonstrates the importance of appropriate seismic data for trap definition. It also offers a caution against pessimistic interpretations of source rock geochemical data and highlights the importance of understanding any down dip hydrocarbon indications.