Impact of differing heat flow solutions on hydrocarbon generation predictions: A case study from West Siberian Basin

Abstract

Knowledge of the thermal history of a sedimentary basin is necessary for the quantitative and qualitative estimation of hydrocarbons generated from buried organic matter. Usually, specialists use a combination of backstripping and forward temperature modelling techniques for a basin history reconstruction. However, this approach decouples the structural and thermal solutions and therefore results in the less consistent modelling. The reliability of a basin model can be increased by using coupled approaches that resolve the structural and thermal solutions simultaneously.In this work, we investigate how using a backstripping-based versus a coupled thermo-tectono-stratigraphic approach for computing basement heat flow influences the predicted total hydrocarbon generation using a 808 km transect across the West Siberian basin as an example. Both coupled and decoupled approaches are used to reconstruct a basal heat flow history for the transect. Corresponding models have identical geological parameters and are calibrated with a set of temperature and vitrinite reflectance data. Furthermore, reconstructed heat flow histories are used separately as a lower boundary condition in a petroleum system model to evaluate the consequences for hydrocarbon generation. We find that the backstripping-based approach significantly overestimates hydrocarbon generation mass with respect to the basement heat flow solution obtained from the more consistent thermo-tectono-stratigraphic model. Also, the onset and time evolution of hydrocarbon generation is substantially different. These findings, obtained for the West Siberian Basin, show that calibrating a thermal model to the wellbore temperature and vitrinite data can lead to the inaccurate interpretation of the thermal history. The study results suggest that the presented advanced basin modelling strategy can help in decreasing risks in petroleum system analysis by providing more reliable and consistent heat flow solutions.