Search

In this article, by using geochemical methods, the effect of CO2injection effect on the asphaltene precipitation and changing of other oil components was investigated. This study was performed in one of the eastern Persian Gulf oil fields with an API of 30.5. For this subject, gas injection was executed with a slim-tube instrument and minimum miscibility pressure was also measured. An asphaltene precipitation test and liquid column chromatography test were conducted on the oil samples retrieved from the slim-tube instrument. This study indicates that CO2influences the oil reservoir properties so intensively that all oil components were changed by the injection. [ABSTRACT FROM PUBLISHER]

This article is an experimental program that was undertaken to investigate miscible gas (methane) injection effect on oil composition during enhanced oil recovery process. In order to perform the injection operation and calculating minimum miscibility pressure, a slim-tube apparatus was used. After that, geochemical tests were employed to investigate the effect of methane injection on oil composition. A chosen oil sample (API 30.5) was taken from “B” field on the eastern side of the Persian Gulf. Although polar components have been affected by the methane injection in a way that asphaltenes and resins content were decreased after injection, non-polar compounds have not been changed at all. [ABSTRACT FROM PUBLISHER]

It is essential that precipitation of asphaltenes is recognized early in the planning stage of any CO2 enhanced oil recovery (EOR) project so that appropriate testing can be performed to evaluate whether there will be a negative impact on reservoir performance. This article presents detailed evaluations of slim tube data that were obtained during CO2 injection using a medium-gravity Iranian crude oil. A crude oil from Bangestan reservoir of Ahwaz oilfield containing 18.2% asphaltenes with ~31.5 °API gravity was flooded by purified CO2 (>96% CO2) in a slim tube apparatus under 2,700 psi at 110°C. We were going to determine the minimum miscibility pressure (MMP) of the sample oil under injection of CO2 flood, but when a CO2 slim tube test was performed for this oil at 2,700 psi, less than half of the saturated oil in the tube was recovered, which implied that the displacement process was immiscible. At this pressure, the asphaltene deposition in the slim tube apparatus was so severe that even a pressure gradient of 6,200 lb/in2 was not able to displace any fluid through the capillary tube. Therefore, we abandoned MMP determination with this sample and investigated the problem. Due to the high percentage of asphaltenes in the sample, using the slim tube MMP as an apparatus for determining minimum miscibility pressure of CO2 and sample oil can be misleading. [ABSTRACT FROM AUTHOR]