How Models of Organic Carbon Distribution are Influenced by Paleo-bathymetry - Tested in the Cretaceous Hammerfest Basin, Barents Sea

Abstract

In basin modelling and petroleum system analysis geometries during deposition of sediments (paleo-water depth) and distribution of organic matter are initial parameters used for further interpretation or modelling. Here we present an approach, combining backstripping with a probabilistic forward sedimentary model to calibrate paleo-water depth (PWD). The stochastic PWD results serve as an input for organic facies models and we demonstrate how the initial PWD will influence models for total organic carbon distribution in a sedimentary basin. We used the Late Cretaceous Kolje Fm. in the Hammerfest Basin as a test case. We reconstructed mainly shelfal to upper bathyal bathymetries (between 118 m and 318 m). Organic facies models using end-member PWD reconstructions as initial input gave an average total organic carbon (TOC) content varying between 0.47 wt% and 5.24 wt%. For the different models absolute TOC values are similar but vertical and lateral distribution pattern change significantly. In general, the study illustrates specific sensitivity for shallow PWD. Small perturbations in the PWD model in the shallow areas relate to substantial changes in source rock properties. We predict that especially in these areas interpretation and mapping of source rock potential can be problematic. The study indicates, that although a large uncertainty in PWD is related to an increased uncertainty in the TOC models it is not possible to relate the two uncertainties a priori. This is an indication on how uncertainty might propagate through an entire stochastic petroleum systems model where other non-linearities can be expected.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018