London Evening Lecture: September 2019

Open to ALL PESGB Members, the PESGB YPs present:

Fresh insights into the under-explored Tertiary injectite play of the Beryl Embayment, UK North Sea

With Thad Cooper, Azinor Catalyst

Tertiary injectites exhibit exceptionally porous & permeable reservoirs and as such represent commercially attractive targets as infill/near field tie-backs but also, more recently, standalone exploration opportunities of their own.

Despite being recognised in the geological record for over 2 decades advancements in 3D seismic data has fostered an appreciation of the reservoir connectivity these features can generate leading to incremental reserves and production lifts being added to declining and mature fields.

Many of the 41 fields in the North Sea whose reservoirs are thought to have a tertiary injectite influence were found serendipitously however, since 2005 and the advent of broadband seismic data, these features are now being specifically targeted. This started in Norweigian waters with the Volund Field in 2005 and then 5 years later at Catcher on the UK side of the median line. The Beryl Embayment of the North Sea Viking Graben represents a hot-spot for injectite exploration targets where there have now been 5 new discoveries in as many years in this emerging play.

There are few areas of the North Sea so well explored without yet a consistent and widely accepted model as to how the reservoirs have been formed and remobilised. Understanding the structural geology of the Beryl Embayment and it’s evolution at a regional scale is key to understanding why this region in particular has become such a prolific injectite province.

Despite injectites being abundantly visible on seismic data in the tertiary units of the Beryl Embayment some disappointing well results have established that not all are hydrocarbon-bearing. The challenge is to try and reliably distinguish the hydrocarbon-filled high poro-perm features from dry or tight reservoirs in the most cost-effective way. High quality broadband Geostreamer surveys allow us to use advanced QI techniques in order to de-risk these features however this only gets us so far as the inherent heterogeneity and often sub-seismic resolution of these injectite complexes means that subtleties simply can’t be captured yet.

As scientists we try to compartmentalise our observations and create a concise set of models based on the evidence presented to us. However the brief exploration history of injectites has taught us more than ever that geology is not an exact science and that these, often unique, features don’t have a ‘one-size fits all’ model, or certainly not one that has been established to date…A holistic approach combining modern geophysical methods and observations with established geological models honouring the mechanics of how injectite features form can provide a more robust explanation as to whether they are plumbed into the petroleum system or not.

This talk will attempt to unravel the secrets of the Beryl Embayment’s tertiary play by focussing on the Agar/Plantain wells drilled last summer which specifically targeted an injectite complex. We will look at how the targets were initially identified using a combination of high quality datasets, regional play analysis and new technology. The results of the wells will be discussed along with our updated models which adds further evidence that this is just the start for this emerging play.

3D structural model for the Beryl Embayment injectite complexes:

3D Balder Mound Surface:

3D view of Agar Plantain Anomalies:

Seismic line through Agar/Plantain and 9/14a-15A (Aragon) well: