Halten Terrace South – 3D Fluid Flow Modelling of Multiple Source Rocks and Reservoirs

Kristian Angard¹ and Øyvind Sylta^2
1Hydro Oil and Energy, Global Exploration, Drammensveien 264, N-0240 Oslo, Norway
²Migris AS, PO Box 1273 Pirsenteret, c/o Leiv Eiriksson incubator 7462 Trondheim, Norway

As a part of standard prospect evaluation in Hydro a full 3D basin modelling is performed. This paper focuses on the workflow in evaluating a basin where at least two source rocks are identified, and where several discoveries show multiple reservoirs.

The first step in the workflow is to construct a 3D basin model (PetroMod) and calibrate the model with respect to maturity of source rocks and pressures in reservoir layers. The results from this modelling are input to probabilistic calculations of expelled oil and gas. The uncertainty range of maturity is therefore recognized and typically described as a most likely maturity case and one/several deviation case(s). The variability source rock thicknesses and qualities is also important to determine at this stage. The final results are in the form of stochastic expulsion maps (e.g. p10, p50, p90) for selected time steps. These maps, together with maps that describe the burial history of the area, are input in the 3D fluid flow modelling. In this particular case performed with SEMI. This sequence of basin analysis provides a powerful tool to both quantify and visualize the uncertainties regarding both volumes within prospects and phase predictions.

An evaluation of the southern part of the Halten Terrace is used to exemplify the prospect evaluation workflow described above. Two main source rocks are recognized in this area, the Upper Jurassic Spekk Formation and the lower Jurassic Åre Formation. Historically there are divergent views whether both of these source rocks have contributed to the known accumulations. The geochemical interpretations reveal that both of the candidates should be included in any prospect evaluation in this area. The final results from the fluid simulations are tuned according to geochemical observations, e.g. how much Åre gas is present in the known accumulations.

The stochastic approach shows a wide range in e.g. phase predictions for individual prospects. This is exemplified for some of the Mid Jurassic prospects in PL 348 west of the Draugen Field, and is very important to communicate into the prospect evaluation.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands