Lateral Compositional Variations in the Upper Jurassic Source Rock in the Southwestern Barents Sea

Abstract

Summary The Upper Jurassic Hekkingen Formation is an important element of the petroleum system in the Barents Sea as the formation is the most prolific source rock in the area and in addition functions as a hydrocarbon seal. Current knowledge suggests that deposition of the Hekkingen Formation occurred during an early stage of rift initiation and a regional transgressional event, causing the detritus to be deposited in a restricted to open shelf environment. Paleogeographic interpretations commonly display the Hekkingen Formation to have a homogenous depositional environment over large areas, but the unit shows great variation in thickness and composition both laterally and vertically, indicating that the current understanding is to general. Two maximum flooding surfaces in the Alge Member of Hekkingen Formation display prominent high value spikes. The prominent spike could be caused by the total organic content (TOC) in the formation, or alternatively the spike could be caused by the mineralogical composition. The preliminary interpretations show that there is a difference in how the gamma-ray signal responds to the TOC content of the wells. This may indicate that other factors than TOC influence the gamma-ray readings in the source rock.