--> Modelling the Distribution of Organic Matter in the Hekkingen Formation (Hammerfest Basin, Barents Sea) for Basin Modelling — A High-Resolution, Three-Dimensional, Process-Based Approach

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Modelling the Distribution of Organic Matter in the Hekkingen Formation (Hammerfest Basin, Barents Sea) for Basin Modelling — A High-Resolution, Three-Dimensional, Process-Based Approach

Abstract

The heterogeneity of source rocks is an aspect that is often ignored in basin modelling studies, but essential in the correct estimation of hydrocarbon generation, migration and trapping. Using a unique process-based modelling tool (OF-Mod) a detailed model was made on the organic facies of the Late Jurassic Hekkingen Formation. The Hekkingen Fm. is approximately time equivalent to other Late Jurassic source rocks: Spekk Fm. (central Norway), Draupne Fm. and Kimmeridge Fm. (North Sea). The Hammerfest Basin during the Late Jurassic has a complicated and poorly constrained tectonic and marine history [1], requiring several scenarios to be tested. The goal of this study was to provide models of the distribution of the inorganic (sand, shale) and organic (TOC, HI) fractions, which will be used as input in a separate basin modelling study [2]. The process-based modelling tool OF-Mod [3] was used to calculate the organic and inorganic properties at time of deposition. Multiple scenarios with varying key input parameters were tested, such as paleo-water depth, sedimentary systems, and the creation and preservation of organic matter. High resolution models were created: 100 layers vertically and 400 × 400 m horizontally. This is essential to reproduce the significant lateral and vertical changes in sand fraction and the organic components. A critical input is paleo-water depth: the basin configuration at time of deposition. This dictates the distribution of the various sedimentary facies. In this study two different paleo-water depth scenarios were tested, based on different tectonic scenarios. The modelled sand fraction in the basin was compared to well data from 11 sites, allowing the informed selection of the optimal paleo-water depth scenario. A second crucial aspect is the extent of anoxia, as this has a large influence on the fraction of organic matter which will be preserved. We compared modelled results (oxic and anoxic) with high resolution measurements of TOC and HI in 25 wells. This allowed the subdivision of the area in an oxygen rich and an anoxic area. Understanding the distribution of anoxia allows us to extrapolate this to areas where no wells are available for testing. This helps predict the possible carbon distribution and provides more realistic input for subsequent basin modelling.