Using Well information to Obtain Marine Palaeoproductivities as Input for 3D Modelling of Organic Carbon Distribution in the Western Barents Sea

Monika Majewska-Bill

A three-dimensional distribution of total organic carbon (TOC) in an area can be obtained by interpolating between measurements in wells, but this would ignore any understanding of the system under consideration. It also precludes any reliable prediction away from the wells. An alternative approach, taken here, involves obtaining a regional distribution of marine primary productivity using measured well values, from which the spatial and temporal productivity variations are reconstructed and used as input in 3D forward modelling. Such an estimate of marine palaeoproductivity is an important input for 3D modelling of TOC distribution in OF-Mod 3D (Organic Facies Modelling 3D). In the approach presented here, measured well values of TOC, hydrogen index (HI) were used to determine organic carbon composition, i.e. marine, terrigenous and residual organic carbon. Once the marine fraction is known, the marine palaeoproductivity can be determined, which requires the following inorganic input data: palaeo-water depth, sedimentation rate, dry bulk density and sand fraction. The inorganic input data in this case are extracted from the stratigraphic (inorganic) part of the OF-Mod 3D model. The back-calculations of TOC and HI values were performed in OF-Mod 1D (Organic Facies Model 1D). The results were used to obtain a regional distribution of marine palaeoproductivity, which was used as input for 3D modelling with OF-Mod 3D. The results of the 3D model are calibrated with the measured values from the wells. This approach uses the process understanding incorporated in OF-Mod (both 1D and 3D) to obtain a regional distribution of source rock potential while using as much as possible of the available information mentioned above. The OF-Mod 3D software was used for a quantitative and qualitative prediction of source-rock potential for two formations: Middle Triassic Kobbe and the Late Jurassic-earliest Cretaceous Hekkingen in Western Barents Sea (on the western part of the Loppa High).

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013