Evolution of Acidic Compounds in Crude Oil during In Situ Combustion

Abstract

In situ combustion (ISC) process has drawn more and more attention in the development of heavy oil reservoirs as a result of its high recovery efficiency. Although numerous studies have been reported that oil properties exhibit significant changes during the combustion process, the reaction mechanisms and evolution of oil components are still not well understood. In this work, the compounds of produced oils collected from a three-dimensional simulated production model (container) at different duration times after combustion being initiated and the original oil were characterized at the molecular level using gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both aromatic and acidic components were analyzed. The aromatic components showed relatively more stable characteristics than those of acidic components, and no obvious changes in aromatic compound distributions were observed by the positive ion atmospheric pressure photoionization (APPI) FT-ICR MS analysis. Small aliphatic acids were detected in the ISC oils, which were responsible for the high total acid numbers (TANs). The acidic O x (x = 1–3) compounds, which have major contributions to the increase in TAN, were generated in greater abundances compared to that of the original crude oil. The carbon number distributions of the O1 and O2 classes in the produced oils significantly shifted to a lower carbon number region, with the dominant distribution from 15–40 at the initial state to 10–30 at the longest duration time. The double bond equivalent (DBE) values decreased during the combustion process. The generated acidic O1 components with DBE values less than 4 were also found in negative ion electrospray ionization (ESI) analysis, indicating the oxidation of hydrocarbons to alcohols.

Analyzing the solid soot particulates formed in a fuel‐rich flame by solvent‐free matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry

“…The concept of DBE numbers is widely used in the research topic of the high‐resolution mass spectrometric analysis of petroleum samples, and the chemical species with identical DBE numbers but different carbon numbers are usually assumed to be the molecules with the same aromatic core but different aliphatic chains in terms of overall chain length. Different from the iso‐abundance plots of typical fossil fuel samples, there are always less than four dots at each DBE row in Figure . This indicates that there are limited aliphatic side chains (less than 4) for these PAHs in the solid soot particulates.…”

Oil-Dispersed α-Fe2O3 Nanoparticles as a Catalyst for Improving Heavy Oil Oxidation

“…Thermal enhanced oil recovery (ThEOR) methods are generally applied for heavy and extra heavy oil extraction, including steam injection, hot water flooding, in situ combustion (ISC), and so forth . The ISC technique has been given much attention recently for heavy oil recovery . ISC is the oldest member of the ThEOR family, and its effectiveness for heavy oil recovery has been proved by many economically successful field applications since the 1920s. , It is basically an air injection process into reservoirs to in situ create a combustion front to push oil to move to producers through multiple displacement of steam drive, distillation, flue gas flood, hot and cold water drive, and so forth. − …”

Evolution of the Properties and Composition of Heavy Oil by Injecting Dry Boiler Flue Gas

“…On the basis of common knowledge of electrospray ionization, the N 1 species, O 1 species, and O 2 species mainly correspond to neutral nitrogen compounds, alcohols, and carboxylic acids, respectively. 38 The N 1 O 1 , N 1 O 2 , O 2 S 1 , O 3 , O 4 , and O 5 species have different functional groups but at least can be ionized by negative-ion electrospray ionization (ESI). The results indicate that the O 2 classes constitute the maximum acid portion of the heavy oil sample before and after the HTHP reaction experiment.…”