A. G. Bhullar*, D. A. Karlsen**1, K. Backer-Owe**, K. Le Tran***, E. Skålnes+, H. H. Berchelmann++ and J. E. Kittelsen+++
*University of Oslo, Norway present address: Institute of Fossil Fuel and Environmental Geochemistry (NRG), University of Newcastle upon Tyne, NE1 7RU, UK.
** Petroleum Geochemistry Program, Dept. of Geology, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway.
1Corresponding author: e-mail: email@example.com.
*** Elf Aquitaine Production, CSTCS Avenue Larribaú, 64018 Pau Cedex, France.
+ University of Bergen. present address: Technoguide asa Aslakveien 14C, N-0753 Oslo, Norway.
++ Norsk Hydro asa, P O Box 200, N-1321 Stabekk, Norway.
+++ BP-Amoco Norway, P O Box 197, N-4065 Stavanger, Norway.
Well logging is used routinely to delineate variations in the physical properties of the water, gas and oil zones in a petroleum reservoir. The analysis of petroleum extracted from reservoir samples is a complementary approach to reservoir screening. For this study, we studied core samples of Jurassic reservoir rock from the Rind discovery (offshore Norway). Bitumen was extracted from these samples using a rapid procedure known as "micro-extraction". The extracts were then separated into compound classes (saturated hydrocarbons, aromatic hydrocarbons and polar compounds) by Iatroscan thin-layer chromatography -- flame ionisation detection (TLC-FID). Using this approach, we show how problematic transition zones in this reservoir, which had not been resolved by logging techniques, were targeted, analysed and categorised. Furthermore, we demonstrate how oil and water zones can be differentiated from residual oil zones, and how the early existence of oil in currently gas-charged reservoir strata can be inferred. Examples from the Hild, Visund and Ula fields from the Norwegian Shelf illustrate the identification of sand bodies which served as highly interconnected "pipelines" during reservoir filling.
The purpose of this paper is to describe and evaluate the combined use of micro-extraction and Iatroscan TLC-FID in reservoir screening. We illustrate the application of this dual procedure using case histories from three oilfields and one condensate field in the Norwegian North Sea.