Resistivity of reservoir sandstones and organic rich shales on the Barents Shelf: Implications for interpreting CSEM data

Marine controlled source electromagnetic (CSEM) data have been utilized in the past decade during petroleum exploration of Barents Shelf, particularly for de-risking highly porous sandstone reservoirs Upper Triassic to Middle Jurassic Realgrunnen Subgroup. In this contribution we compare resistivity response from CSEM wireline logs both water- and hydrocarbon-bearing wells. We show that there is a very good match between these types data, when are shallow. however, only provide information on subsurface resistivity. Careful, geology-driven interpretation required maximize impact success. This important quantifying relative high-saturation overlying cap rock. presented case rock comprises predominantly organic rich Jurassic–Early Cretaceous shales Hekkingen Formation (i.e. regional rock). The reservoir its become merged due transverse resistance equivalence principle. As result this, it imperative understand contributions rock, geological significance any lateral variation each units. contribution, quantify mudstone, i.e. sandstones, using 131 boreholes Shelf. highest (>10,000 ??m) evident Subgroup which reported 48 boreholes, 43 used study. Pay zone primarily by quality porosity shale fraction) fluid phase gas, oil water saturation). investigated wells, dominated exhibits enhanced compared background underlying stratigraphy), though rarely exceeds 20 ??m. mudstones typically correlation measured richness resistivity/sonic velocity log signatures. conclude sandstones outweighs rocks.