A good understanding of the interactions between the fractions of Saturates (S), Aromatics (A), Resin (R) and Asphaltenes (A) of crude oils is of great significance for in-situ combustion (ISC). However, due to the vast physiochemical diversity of different crudes, the current data base is not yet sufficient to yield a conclusive combustion map. To add further data to the existing data base and to specifically determine the SARA interactions of an extra-heavy oil, we present combustion results from TG/DSC experiments and model fitting using the crude oil, individual fractions and their binary mixtures (S/A, A/A and R/A). The TG/DSC curves have shown clear evidence for the different combustion pathways of the SARA fractions with temperature. The alterations of peak temperature, heat release, temperature interval, activation energy (E-a), etc., of the binary mixtures revealed the interactions between SARA fractions during nonisothermal combustion. Asphaltenes tended to reacted with the products of saturates and aromatics LTO (low temperature oxidation) reactions, whereas resins did not alter the combustion pathway of asphaltenes presumably due to their similar structures. Saturates and resins can reduce the E-a of asphaltenes HTO (high temperature oxidation) as a result of the boosted coke formation. On the contrary, aromatics inhibited the LTO and HTO combustions, as verified by the increased E-a of these two stages.

Abstract The depression of the current global oil market renders the majority of chemical EOR projects worldwide unprofitable, especially in china. Therefore, economic alternative technologies must be quickly developed. This paper evaluated the potential of a smart pre-formed emulsion flooding EOR in Block 9 based on the reaction between alkali and highly acidic crude oil. The static properties and dynamic displacement behaviors of the emulsion were thoroughly investigated. Particular emphasis was placed on the relationship between emulsion stability, droplet particle/pore radius matching, and EOR efficiency. The experimental results showed that the petroleum acids of the crude oil reacted with alkali (NaOH), and producing neutral emulsions (pH≈7.0). The emulsion rheology and morphology were strongly dependent on oil water ratio. From the economic point, the oil/water ratio of 0.5:9.5 was used to prepare two types of O/W emulsions (unstable and stable emulsions) with different particle sizes. The core flooding tests proved that a higher pressure during emulsion injection was generated than that of water injection due to Jiamin effect induced by the dispered oleic phase. As a consequence, the oil recovery factor was further improved by 6-17%. High matching factor and emulsion stability accounted for more significant EOR effect as we observed.

The depression of the current global oil market makes the majority of chemical EOR projects worldwide nearly unprofitable, especially in China. Therefore, economic alternative methods and technologies must be quickly developed. This proof of concept research evaluates a chemical flooding method using pre-formed mild O/W emulsions, which were produced by saponification between a low-cost alkali (NaOH) and a petroleum acid-rich oil. Our focus was first given to the dynamics of the saponification with an aim to quantify alkali consumption. Afterward, the composition of the crude oil before and after the reaction was characterized using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) to determine the preferred compounds in saponification. The physiochemical properties of the generated emulsions were further investigated through direct measurements of rheology, morphology, particle size distribution, and stability. Particular attention was placed on the oil displacement mechanisms of the emulsions at pore level. The results showed that fatty acids, naphthenic acids, and aromatic acids were clearly partitioned on the FT-ICR MS spectra of the crude oil, while the C16 and C18 fatty acids (DBE = 1, DBE represents equivalent double bond number) were predominantly saponified, which accordingly produced mild O/W emulsions (pH approximate to 7.0). The viscosity, morphology, and stability of the emulsions were found to strongly depend on the oil-water ratio. The displacement dynamics of three stable emulsions observed in a visual micromodel revealed that the O/W emulsion flooding can enlarge the sweep area and also notably reduce the residual oil saturation when employed as an EOR mode. Emulsification/entrainment, blocking, and stripping were three dominant pore level driving forces for this emulsion flooding. Phase inverse from O/W to W/O occurred when the emulsion of O/W = 3:7 was used and finally caused injectivity issue.

The geochemistry of a reservoir is of great significance for CO2 Enhanced Oil Recovery (CO2-EOR) and CO2 geosequestration operations. However, due to the massive diversity in mineralogy and physicochemistry of different reservoirs, the current data base is not yet sufficient to conclusively determine the alterations of geochemical prosperities when CO2 is injected especially for tight reservoirs. The attention of this work was given to a tight sandstone reservoir in Lucaogou formation of Jimsar sag (China). The interactions of reservoir rocks, formation brine and supercritical CO2 were extensively investigated under reservoir conditions (75 degrees C and 32 MPa) aiming to reveal possible mechanisms behind. The results showed that the dissolution of supercritical CO2 in the brine created an acidic environment (solubility = 0.94 mol/Kg), which induced the dissolution of minerals into the brine and their subsequent precipitation. The primary precipitants in this work were found to be iron minerals and kaolinite, as evidenced by Scanning Electron Microscopy and Energy Dispersion Spectrum (SEM-EDS) analyses. Moreover, the SEM-EDS observations have shown clear signs of mineralogical changes of the rocks with the preferred dissolution of K-feldspar, albite and ankerite. Kaolinitation due to the corrosion of Kfeldspar and albite occurred during the CO2-exposure experiments. The mineral surface after exposure to CO2 was altered to be more water-wet as a result of mineral dissolution, kaolinite formation and surface corrosion.