Validation of a Pseudocomponent Scheme for Nigerian Heavy Oil and Bitumen

Abstract

AbstractRecently, a set of six pseudocomponent (PC) schemes was proposed for general characterisation of the Nigerian heavy oil and bitumen 1. However, the performance of the schemes is yet to be assessed. Given the laboratory-measured viscosity versus temperature relationship of a sample of the Nigerian bitumen, this paper employs the PC schemes to construct and tune fluid models to the viscosity dataset. Although all the cases show reasonable agreements (average absolute deviation below 25%) between measured and fitted data, the best and worst performances are obtained with the 4-PC and 1-PC schemes, respectively.The tuned fluid models are then applied in thermal reservoir simulation studies. With a generic but representative reservoir-sector model, the dynamic response of the Nigerian bituminous deposit to the recovery method of steam-assisted gravity drainage (SAGD) is investigated. Simulation results indicate excellent consistency among the 3, 4, and 5-PC schemes but the 1- and 2-PC schemes deviate markedly from the higher-component approximations. As might be expected, the 1-PC model can not explain the solution gas reported in the Nigerian bituminous belt.From the specific case studied, at least three PC's may be required to enable satisfactory characterisation of the Nigerian heavy crude for general applications. This initial conclusion follows from the comparative accuracy and computational efficiency of the ternary (3-PC) model. Future efforts should focus on generating additional experimental datasets, including but not limited to viscosity, on the Nigerian bitumen and evaluating the robustness of our preliminary conclusion.