Using Oil Tracers to Model Petroleum Migration

Abstract

Understanding the characteristics of oil migration through the subsurface after oil has been generated in the kitchen area is vital for predicting potential hydrocarbon accumulations or to quantify the volumes of known ones. We present a numeric model based on a set of hydrocarbon tracers that is designed to calculate the migration distance and timing for the oil flowing from the source to the reservoir accumulation. The tracers we are using for numeric simulation are a family of molecular markers naturally present in crude oil, such as carbazole and its derivatives. These markers are nitrogen‐based aromatic compounds that are generated with the oil and are specific to each source rock. The hydrocarbon tracers modeled continuously change their absolute and relative composition along a migration pathway due to processes including generation, partition, diffusion, and adsorption. The model calculates the distribution in space and time of tracer concentrations and then converts the distribution to migration distance. In the first step, the model determines the initial concentration of tracers before the oil migration starts. This is achieved by using a set of kinetic parameters, specific to each tracer, in a generation module designed to estimate the original tracer composition present in the generated oil. Laboratory experiments were performed to infer the kinetic parameters for specific source rocks. To test our model, we used the tracer model to estimate the potential for oil accumulation in a reservoir structure. Using the calculated migration distance and timing, we determined the filling sequence of accumulations. From this sequence, we conclude that the closure probably received charge via a spill from an adjacent accumulation. The concentration of multiple tracer components from the known accumulations were used to calibrate the model. The tracer model offers a method to calibrate basin simulations and map‐based analyses for the migration distance and timing when tracer measurements are available anywhere within the basin being explored. The calibration would enable an improvement in the accuracy of the predicted migration path and accumulation spilling sequence.

AAPG Datapages/Search and Discovery Article #90349 © 2019 AAPG Hedberg Conference, The Evolution of Petroleum Systems Analysis: Changing of the Guard from Late Mature Experts to Peak Generating Staff, Houston, Texas, March 4-6, 2019