Risking Basin Analysis Results III. Effects of Uncertain Geochemical Parameters on Hydrocarbon Generation

Abstract

This paper considers the effect of uncertainty in geochemical kinetic parameters on the production of oil and gas from kerogen in a basin. Three kerogen types are considered with different fractional breakdowns to oil and gas. The illustration uses three kinetic parameters for each of the kerogen types so that in total one has available 12 parameters. Allowing only the kinetic parameters associated with the kinetic breakdown to vary by up to ±50% around nominal values, one can determine under what conditions it is necessary to be concerned about refining better the uncertain parameters and also one can determine which parameters need to first be sharpened in order to improve resolution on the hydrocarbon generation. The argument presented here can be applied to any proposed kinetic scheme for converting kerogen to oil and gas. The example presented shows that the broad range of times and depths that will produce hydrocarbons are such that changes in the kinetic parameters, even by the large factor of 50%, produce less than about a 10% uncertainty in the total amount of oil and gas generated so that there is little need to try to narrow the wide dynamic range of the geochemical kinetic parameters. This insensitivity of hydrocarbon generation to precise values for the kinetics has been seen before in isolated case studies, but the use of a fast Excel basin analysis code together with the risking code Crystal Ball, strengthens the argument to a very wide swath of conditions – something that was not easy to do before the high speed Excel basin analysis code was available.