3-D Restoration of the Dutch Central Graben: Predicting Prospects in the Chalk Plays (2016)

This MSc thesis has been written by former intern Folkert van Straaten.

Chalk structures in the Central Graben of the North Sea Basin were deformed by halokinesis. Halokinesis in the North Sea Basin has been studied over decades, but remains poorly understood. Halokinesis is known to have affected several aspects of hydrocarbon plays in the Central Graben: by affecting the maturity of the source rock, influencing the migration paths of hydrocarbons, and affecting trap formation. Therefore, a detailed understanding of how the salt flow has affected its overburden is crucial for successful hydrocarbon exploration and a better understanding of the halokinesis, can potentially result in an increase in success rate of the exploration of the petroleum plays in this part of the world.

Structural restoration is a technique that provides inside in the deformation history of an area. Already many 2-D sections across the North Sea Basin were restored to give inside in the deformation history. However, an area affected by halokinesis and also having a complex structural character, cannot be restored in two dimensions without violating the main assumption; that is no volume is moving in and out of the plane of section. Therefore in this study a 3-D restoration is made, so volume is preserved while restoring the area.

In this study the area is restored till the Early-Cretaceous because of two reasons: first more details (more horizons, smaller geological events) can be included in the restoration, second the most important plays in this area are the Chalk plays which were formed during the Late Cretaceous. By restoring the area till the Cretaceous, the deformation of several horizons through time was visualized. Based on these results, an analysis of the hydrocarbon generation, migration and trapping was performed. It was assumed that the Posidonia Shale is the source rock for the hydrocarbons in the area. The hydrocarbons migrated, through the Middle Graben formation, until they spilled into the Chalk members (Maastrichtian and Danian). In these members the hydrocarbons were trapped. Using this model an analysis was made where the hydrocarbons could possibly be trapped. This was tested against well data.