Assessing Source Rock Characteristics from Calibration Against Known Accumulations in Petroleum Systems Modeling: Sensitivity Analysis and Resolution

Thomsen, Rene O., Niels Langager Westphal, Lene F. Clausen, Nils Lange Jacobsen, Maersk Olio og Gas AS, Copenhagen, Denmark

Hydrocarbon accumulations are direct evidence of active working petroleum systems. The accumulated fluids define “end-points” on migration pathways and their composition and chemical characteristics are results of their respective source rocks’ characteristics and maturation history as well as influence from the environment through which they migrate and accumulate. Source rock characteristics, spatial distribution and variation based on out­crop data and well penetrations provide the initial source rock model. In petroleum systems modelling reservoir fluids are viewed as products of the initial - often multiple - source flu­ids reflecting the generation, migration and reservoir conditions. Detailed analyses are thus vital for improving the understanding of the source-reservoir relationships.

When multiple source levels are present it is often difficult to intuitively understand their relative importance and contributions to specific accumulations. Likewise, unravelling the direct impact that multiple source levels have on the characteristics of the observed reser­voir fluids is not straightforward. 3D petroleum systems modelling is an effective tool for obtaining insight into the source rock model and understand the sensitivity of the spatial and temporal relationship between sources and reservoir fluids. This study illustrates calibration of source rock parameters against fluid properties and a sensitivity analysis for two source rocks against fluid properties in five near-by, producing fields. TOC and HI for each source rock are varied systematically and modelled with the predictions being compared to observed fluid properties. The work demonstrates the ability to calibrate source rock char­acteristics from fluid properties and how the sensitivity analysis constrain relative contribu­tions from each source to the individual fields as well as delineate specific migration routes and reservoir filling histories.