Compositional Grading and Reservoir Oil Composition Variation with Depth Experiment by PVTi Software with Lab Data

Abstract

Heavier molecules tend to migrate towards the bottom of column. Gross assumptions in PVT experiment are that the system is in gravitational and diffusive equilibrium. Starting from an oil and moving up a column, the fluid will become lighter and tend towards a gas (condensate). Two types of grading are possible. The first one is of the fluid going from an oil to a gas with a distinct gas-oil contact at some unique depth. If this situation occurs, it will be predicted. The second one is the Fluid grading from an oil to a gas without a contact. This case corresponds to the critical temperature of a composition within the reservoir equalling the reservoir temperature. In compliance with compositional grading study, the API and some properties of the reservoir oil composition such as sulphur and CO2 contents vary with the reservoir depth. Most of the time the gas-oil contact (GOC) is named as the reservoir datum depth. In this paper, the study of compositional grading and reservoir oil composition variation with depth experiment by PVTi software with lab data has been achieved and some good conclusions have been gained.