The low-temperature catalytic oxidation of heavy crude oil (Xinjiang Oilfield, China) was studied using three types of catalysts including oil-soluble, watersoluble, and dispersed catalysts. According to primary screening, oil-soluble catalysts, copper naphthenate and manganese naphthenate, are more attractive, and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil. The heavy oil compositions and molecular structures were characterized by column chromatography, elemental analysis, and Fourier transform infrared spectrometry before and after reaction. An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity-temperature characteristics. Results show that the two oil-soluble catalysts can crack part of heavy components into light components, decrease the heteroatom content, and achieve the transition of reaction mode from oxygen addition to bond scission. The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil (oil viscosity and contents of heavy fractions). It is found that the temperature, oil composition, and internal molecular structures are the main factors affecting its flow ability. Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.
Microgel can be used as a novel deep profile control (conformance control) agent in the aspect of EOR(Enhanced oil recovery) in mature oil field development. Dispersion polymerization of microgel has been successfully carried out in aqueous AS (ammonium sulfate) media by using AM (acrylamide), PEG 200 DA (Poly(ethylene glycol(200) diacrylate)), PVP (Poly(vinyl pyrrolidone)), V-50(2,2’-azobis(2-amidino-propane) dihydrochloride), as the monomer, cross-linker, stabilizer and initiator, respectively. The effect of ammonium sulfate and Poly(vinyl pyrrolidone) concentrations are strongly on microgels successfully polymerization. POM(polarization microscope) and SEM (scanning electron microscope)results show that the shape of microgels is in oval or nonspherical state. The surface structure of microgel is rather accidented full of mesoporous. Addition of inorganic salts interacting with poly(acrylamide) microgel can affect its micromorphology and results in the appearance of single crystal clusters. Sand pack flowing experiment shows that the microgel has perfect propagating property during the process of injection and can achieve a high oil recovery efficiency of 23.4% by the total of 0.4 PV microgel solution injection.
To improve the understanding of the influence of effective permeability, reservoir temperature and oil-water viscosity on relative permeability and oil recovery factor, core displacement experiments had been performed under several experimental conditions. Core samples used in every test were natural cores that came from Halfaya oilfield while formation fluids were simulated oil and water prepared based on analyze data of actual oil and productive water. Results from the experiments indicated that the shape of relative permeability curves, irreducible water saturation, residual oil saturation, width of two-phase region and position of isotonic point were all affected by these factors. Besides, oil recovery and water cut were also related closely to permeability, temperature and viscosity ratio.
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