Integration of Biodegradation and Migration of Hydrocarbons in a 2d Petroleum Systems Model: Application to the Potiguar Basin, Ne Brazil

Abstract

Biodegradation is probably the most important in‐reservoir alteration process and is responsible for the majority of the known heavy oil accumulations. In the present study, biodegradation processes were integrated within a forward basin and petroleum systems model applied to the Potiguar Basin, NE Brazil. This basin was chosen because it has been studied in detail and data from previous investigations are publically available. In order to account for processes occurring during the biodegradation of hydrocarbons, the evolution of fluid properties was simulated through time. In the model, a new approach was developed in order to determine the intensity of microbial activity and the evolution of the oil‐water contact, the zone within which biodegradation is confined. The numerical results obtained by applying the forward simulator to a 2D model of the Potiguar Basin fit the observed data concerning the composition and quality of the oil in a series of oilfields. These accumulations are located along the NE‐SW oriented “Carnaubais trend” and show progressive biodegradation along the migration path from the offshore kitchen area. Our results show that the biodegradation trend observed along the cross‐section can in general be explained by the fact that reservoirs are successively filled as a result of spilling from previous reservoirs, with continuous hydrocarbon degradation occurring within the reservoirs. This charge history resulted in differences in the composition of oils transported from upstream to downstream reservoirs, and in the evolution over time of the ratio between biodegradation and reservoir filling rates. Thus, in addition to residence time in the biodegradation temperature window, the rate of reservoir infill, the rate of oil degradation and the migration pathways are key factors controlling biodegradation. This study also demonstrates how the approach developed within our petroleum system simulator, which integrates both migration and biodegradation, may improve the assessment of oil quantity, quality and migration timing.

An Assessment of Stress States in Passive Margin Sediments: Iterative Hydro-Mechanical Simulations on Basin Models and Implications for Rock Failure Predictions

“…As a result, the value of integrating non-vertical stresses in the modelling of passive geological settings appears more questionable, especially when considering the associated increase in computation costs. Basin modellers often deal with passive margin sediments as one-dimensional mechanical systems through geological ages [68][69][70], in line with simplistic models for horizontal stresses computation and the assumption that the maximal principal stress is perfectly aligned with the vertical axis [18].…”

Combining biodegradation in 2D petroleum system models: application to the Cretaceous petroleum system of the southern Persian Gulf basin

“…and other aspects such as reservoir geometry and filling rates and oil composition (Blumenstein et al 2008). In recent years, enhanced software capabilities have enabled scientists to fully integrate biodegradation within petroleum system models (Adams et al 2013;Ducros et al 2016). In this study, we have tried to integrate the biodegradation process in a 2D petroleum system model for the first time in the southern Persian Gulf basin.…”