Using AVO to Evaluate a Thin Pay - A Norwegian Case Study - An Update

Recent progresses in seismic acquisition have paved the way for renewed prospect evaluations. In this paper, we present the example of a Palaeocene-aged prospect offshore Norway. It was identified several years ago but seen as non-economical.

A new broadband seismic dataset was used to re-interpret the prospect. AVO-based methods helped tackle the main difficulty associated to the poorly constrained geometry of this low relief prospect. Presumably, the seismic response of the prospective pay-interval results from the interference between a top hydrocarbon sand and an interpreted fluid contact within the massive sand body.

Nominally, this interval is thinner than seismic resolution. Taking advantage of the different AVA behaviors of these interfaces, top and base pay could be picked independently. Top reservoir was revisited shallower than previously and thickness estimated clear of tuning. Furthermore, the way amplitudes at a selected angle tune as a function of un-tuned thickness allowed de-risking the nature of the fluid fill in comparison with nearby oil and gas fields.

Finally, the well that was subsequently drilled proved the picking strategy right. The discovery confirmed the interpreted oil fill. This paper is an update of the original paper presented at the 76th Conference in Amsterdam.