Play Concepts Based on New Stratigraphic Methods: Two Examples from the Dutch “Upper Jurassic” Offshore of Enhanced Exploration Potential

Abbink, Oscar A., Harmen F. Mijnlieff, Dirk K. Munsterman, Roel M.C.H. Verreussel, TNO-NITG, Utrecht, Netherlands

    The Upper Jurassic – Lower Cretaceous strata are a target for the oil and gas exploration in The Netherlands. During the initial stages of the Dutch offshore exploration history, various oil fields and some gas fields were discovered of which only the F3-FB field proved to be economic. In the Dutch Northern Offshore, uppermost Middle Jurassic (Callovian) - lowermost Cretaceous (Ryazanian) strata are mostly limited to the Central Graben and Terschelling Basin. The geology of this non-marine to shallow marine strata is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sealevel and climate changes, salt tectonics and structural differences hamper straightforward seismic interpretation and log correlation.

In the last years, new biostratigraphic techniques and newly acquired stratigraphic data have led to the identification of a series of events which can be related to the tectonic, cli­matic environmental and stratigraphic development of the “Upper Jurassic”. Based on this data, three tectono-stratigraphic sequences (1, 2, and 3) can be recognized. These insights have directly impact on the exploration potential. For sequence 1, stratigraphic traps in the deeper part along the basin axis are formed within paralic and fluvial deposits. In sequence 3, sponge reefs, growing due to special paleoenvironmental conditions, form reservoir units along the basin edges and on intra-basinal highs within structural traps. In these two exam­ples, the existence of only one economic oil field and the (mis)placement of exploration wells will be explained. The paleoenvironmental understanding is essential for future explo­ration potential.