During the Late Cretaceous and Early Paleocene, deep-water depositional systems deposited sandstones in the Norwegian Sea. The reservoir quality is variable and difficult to predict because of variations in facies, burial depth and temperature history. High- and low-density turbidity currents were the dominant transportation processes of these sands, but debris flow deposits and cross-laminated sediments deposited by sustained sea floor currents occur. The grain size and total clay content have a major influence on the reservoir quality. Reservoirs deposited by turbidity currents have the coarsest and most clay-poor sediments, and the highest porosity and permeability. Superimposed on the facies related reservoir quality trends, is a general trend of decreasing porosity and permeability with increasing burial depth. Given similar facies and similar burial depth, variation in the temperature and burial history results in completely different reservoir qualities. High heat flow and late structural uplift resulted in anomalously poor reservoir quality at present burial depth.
Depositional facies and reservoir quality of deep-marine sandstones in the Norwegian Sea