A Fundamental Micro Scale Study of the Roles of Associated Gas Content and Different Classes of Hydrocarbons on the Dominant Oil Recovery Mechanism by CWI

Mojtaba Seyyedi,Mehran Sohrabi,Pedram Mahzari

doi:10.1038/s41598-019-42226-6

Abstract

Various studies demonstrated new gaseous phase formation and oil swelling and viscosity reduction are the oil recovery mechanisms by carbonated water injection (CWI) with new gaseous phase formation being the major recovery mechanism for live oil systems. However, none of the previous studies investigated the influences of dissolved gas content of the oil and oil composition, on the new gaseous phase. This study attempts to provide insights on this area. Based on the results, during CWI as CO2 partitions into the oil the dissolved gas of the oil liberates, which leads to in-situ new gaseous phase formation. The dissolved gas content of the crude oil has a direct impact on the saturation and growth rate of the new gaseous phase. The new gaseous phase doesn’t form for oils that have an infinite capacity for dissolving CO2, such as light pure hydrocarbon components. Oils with limited capacity for dissolving CO2, such as heavy hydrocarbon components, are responsible for the formation of the new gaseous phase. Therefore for a live crude oil, the relatively heavier fractions of oil are responsible for triggering of the new gaseous phase and light to intermediate oil components control the further growth of the new gaseous phase.

Highlights

Through an extensive series of high-pressure and high-temperature coreflood[23,24,25], PVT26, micromodel[23,27,28] and slim tube[26] experiments, as well as using fully CH4-saturated crude oils, we revealed the positive impact of the presence of associated gas in crude oil on the performance and oil recovery mechanisms of carbonated water injection (CWI)
We found that as soon as CW front comes in contact with the fully CH4-saturated crude oil and CO2 partitions into the live oil, the CO2 pushes the CH4 out of the solution, which leads to the formation of the new gaseous phase[26]
These results indicate that the presence of associated gas in crude oil is vital for the new gaseous phase formation

Summary

Introduction

Through an extensive series of high-pressure and high-temperature coreflood[23,24,25], PVT26, micromodel[23,27,28] and slim tube[26] experiments, as well as using fully CH4-saturated crude oils (live crude oils), we revealed the positive impact of the presence of associated gas in crude oil on the performance and oil recovery mechanisms of CWI. Www.nature.com/scientificreports carbonated water into a fully-CH4 saturated crude oil (live crude oil) led to the formation and growth of a gaseous phase inside the oil phase This phenomenon was not observed for the carbonated water-dead oil system[24]. The impacts of two important factors, which are the associated gas content of the oil and the oil composition, on the formation and growth of the new gaseous phase have not been fully investigated and require a fundamental study at pore scale. Through this study, we attempted to comprehensively investigate the impacts of these factors on the new gaseous phase With this objective, a series of high-pressure and high-temperature direct-flow visualization (micromodel) experiments were designed and conducted. Dynamic fluid-fluid interactions, at micro-scales, were observed at a pressure and temperature of 2500 psi and 38 °C

Objectives

Methods

Results

Conclusion