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.

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In situ combustion (ISC) is one of the improve recovery methods with a high potential to increase the recovery of heavy crude oil. Although we mentioned this major advantage, this process has not being used in Colombia yet. This fact due mainly to the complexity of the involved phenomenon, therefore a field project must be design after extended laboratory investigation. Experimental tests in combustion tubes made through the main conditions in the oilfield have being the process' evaluation tool with the highest acceptance. These tests show the speed and stability of the combustion front and the obtained results from the production's analysis of fluids, mainly the ones of the exhaust gases. It is possible to calculate the basic combustion parameters by using: combustible consumption, required air, air- combustible relation, hydrogen- carbon atomic, and oxygen use. The parameters mentioned before let, trough different scaling analytic methods to evaluate the technical and economic viability of the process in the field. In this work was developed a computational tool that allow calculating the design parameters through different scaling analytic methods Nelson & McNeil, Gates & Ramey y Moore et al). Comparing the results got from the different described methods, when scaling two tests in a combustion tube, they show similar numbers. Taking into account that Nelson and McNeil's method is the most useful one due to the oilfield characteristic, it was made a sensitivity of operational parameters and the result permitted to study the relation between the oilfield operational variables

This work shows the compositional effect on low-temperature oxidation of crude oils subjected to in situ combustion (ISC). Three heavy crudes were used in this study in which detailed information on the molecular species involved in ISC was obtained by ultra-high-resolution mass spectrometry. The oxidation was carried out on a mixture of 2% of crude oil in Ottawa sand in an isothermal cell using a batch system at 1500 psi at three conditions: (i) reservoir temperature of each crude oil, (ii) 180 °C, and (iii) 180 °C using a heterogeneous catalyst-type β-MnO 2 . The oil remaining after the reaction was extracted from the sand and characterized by FT-ICR MS using (+) atmospheric pressure photoionization and (−) electrospray ionization modes. The acidity of the oxidation products (extracts) and the composition of the produced carbon oxides were also monitored. A greater amount of carbon oxides produced, a lower extraction yield of organic matter in the sand after the reaction, and a higher acidity in the extracts, implied a higher reactivity. In the same sense, a higher reactivity was observed for the sample with the highest sulfur content and over the most aromatic compounds. The use of the catalyst at 180 °C promoted the oxidative reactions in two of three of the oils, as well as the formation of polyoxygenated acids over monocarboxylic acids for one of the oils, which implies that the application of this technology strongly depends on the composition of the oil.

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