Exploring Compositional Changes along In Situ Combustion and Their Implications on Emulsion Stabilization via Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

Abstract

In situ combustion (ISC) is one of the highest potential enhanced oil recovery (EOR) processes for heavy oils. However, several operational issues, including the formation of highly stable emulsions, have limited its application. Disclosing the physicochemical proprieties of these emulsions, especially the chemical nature of the compounds involved in the stabilization process, has become relevant for the success of ISC projects. In the present work, the physicochemical changes at a laboratory-scale low-temperature oxidation (LTO) regimen performed over a Colombian heavy crude oil were followed by mass spectrometry. The compositional analyses were performed using both positive-ion atmospheric pressure photoionization ((+) APPI) and negative-ion electrospray ionization ((−) ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Further isolation of acidic compounds and surface-active species allowed us to determine that the process incorporates a wide variety of compounds to build up the O/W (oil/water) interface, thus increasing the stabilizing tendency of the emulsions. During the combustion, oxygen is chemically incorporated to the crude over hydrocarbon compounds, as well as over sulfur- and nitrogen-containing compounds, generating classes such as O, O2, O3, O4, OS, NO2, and NO3 that explain the high viscosity and high stability of the emulsions.

Compositional Effect on the Low-Temperature Oxidation of Crude Oils Subjected to In Situ Combustion

“…When using oxygen as an oxidant, multinuclear systems react readily as more rings are fused because less π-sextets can be shared and more double bonds are formed within the structure, and thus, the addition of oxygen is favored . Therefore, it can be concluded that under the reaction conditions employed, a preferential oxidation of the polyaromatic species occurred, which agrees with a previous study . In this order of ideas, it was observed that at 180 °C with and without the catalyst, compounds C29–31 with DBE 5 were concentrated, which could be associated with mono-aromatic hydrocarbon species refractory to the oxidation process, without ruling out that the derivatives of steranes and naphthenic compounds are also part of this group of compounds.…”

“…When the reactions occur at 180 °C, the percentage of acids was almost the same for RU and CH (35 and 37%, respectively) and almost double for CA (61%). This acidity changes could be related to the formation of oxygen compounds due to LTO reactions as was found previously Figure also shows that the catalyst reduced the percentage of acids in the RU, but it increases in CH and CA.…”

“…This acidity changes could be related to the formation of oxygen compounds due to LTO reactions as was found previously. 25 Figure 3 also shows that the catalyst reduced the percentage of acids in the RU, but it increases in CH and CA. These findings corroborate the effect of the catalyst on the increase of reactivity for CH and CA.…”

“…studied the composition changes along ISC using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), after analyzing the changes of an oxidized heavy oil at two conversion levels. As a result of this research, it was concluded that nitrogen- and sulfur-containing compounds, as well as high aromatic compounds, have a high oxidation tendency . Guan et al studied the oxidation of one light crude oil at an oxygen-reduced air flooding and low-temperature oxidation.…”

“…As a result of this research, it was concluded that nitrogen-and sulfur-containing compounds, as well as high aromatic compounds, have a high oxidation tendency. 25 Guan et al 26 studied the oxidation of one light crude oil at an oxygen-reduced air flooding and lowtemperature oxidation. The main purposes of this work were to establish the limits in temperature of the low-temperature oxidation regime and calculate the activation energy for different oxidation stages.…”