Correlation of Heterolithic Sediments and the role of Differential Compaction. Example from the Åre Formation in the Heidrun Field, Offshore Mid-Norway

Hammer, Erik¹ (1) Tne Norwegian University of Science and Technology, Trondheim, Norway

Correlation of sandstone units in heterolithic reservoirs is in many cases difficult, especially in fluvial sediments where there are large lateral lithological differences. Complexities may in addition be imposed by diagenetic factors such as differential compaction. During burial, heterolithic sediments may undergo differential compaction due to differences in compaction factor for different sediment types; e.g. clay, sand, coal etc. Poor understanding of the reservoir units may cause difficulties during pressure supported production because of uncertainties concerning reservoir connectivity. In this study we examine possible effects of differential compaction on reservoir correlation within the Upper Triassic - Lower Jurassic Åre Formation at the Halten Terrace offshore Mid Norway. The formation consists of lower fluvial plain to lower delta plain sediments including channels and coal beds, showing large thickness variations in the reservoir zones. A comparative study of 19 wells has been carried out for correlation by 1) lithostratigraphic and sequence stratigraphic methods, 2) investigating diagenesis and compaction, and 3) revised correlation by considering effects of diagenesis and differential compaction. The aim is to investigate if effects of differential compaction in a heterogeneous reservoir are recognizable and/or if they are important factors concerning reservoir connectivity.