Detailed Hydrocarbon Analysis of Reservoir Fluids of Some Oil Fields of Upper Assam Basin (India)

Abstract

This study is an attempt to understand the role played by different formation water and crude oil samples in chemical enhanced oil recovery. The study pertains to the characterization of these samples in Agilent Gas Chromatography-Mass Spectrometry in order to determine the organics. The organics were further analysed in the library database of the National Institute Standards and Technology, to identify saturated and unsaturated compounds, organic alcohols and carboxylic functional groups in hydrocarbons. The presence of naphthenes and aromatics was also detected. Crude oil samples showed the presence of saturated and unsaturated hydrocarbons, with a predominance of –OH and –COOH functional groups in the hydrocarbons. While the formation water samples showed the presence of unsaturated hydrocarbons and hydrocarbons containing the –OH functional group with the predominance of saturated hydrocarbons. The presence of –COOH in the reservoir fluids, during the alkaline enhanced oil recovery, leads to the formation of in situ surfactant. The presence of –OH in the reservoir fluids leads to the reduction of wettability between the porous media and the oleic phase. The total acid number of the crude oil increases due to the presence of naphthenic acid, which is formed by the reaction of naphthenes with the –COOH group. The predominance of –OH and –COOH functional groups in crude oil samples enhances the release of more oil from the negatively charged clay surfaces of the Upper Assam Basin.