The low flow characteristics of heavy oil have brought many challenges to its exploitation. Looking for a cost-effective crude oil flow improver to reduce the viscosity of heavy oil is currently the most important challenge. Small-molecule crude oil flow improvers meet the above requirements and become an ideal target for oilfield heavy oil production. In this article, three kinds of barium salts of alkylbenzene sulfonates with different lengths of alkyl chains were synthesized from alkylbenzene sulfonic acid and barium hydroxide. Among them, the viscosity reduction effect of barium dodecylbenzenesulfonate (BaDBS) is best as the dosage is 900 mg/L, the viscosity reduction rate is 89.0%, and the pour point is reduced by 5°C. Optical microscopy revealed the eutectic effect of crude oil flow improver and saturated hydrocarbon in heavy oil. FTIR and DSC were used to research the mechanism of small-molecule crude oil flow improver to reduce the viscosity of heavy oil.
In this work, three multi-alkyl polyamines, i.e., pentahexadecyl diethylenetriamine (PHDETA), hexahexadecyl triethylenetetramine (HHTETA) and heptahexadecyl tetraethylenepentylamine (HHTEPA), were synthesized and evaluated as pure flow improvers for crude oil. Under certain conditions, PHDETA, HHTETA and HHTEPA were able to improve the flow properties of L401 crude oil samples by reducing the viscosity of the crude oil by 97.5%, 94.3% and 97.1%, respectively. The three synthesized alkyl polyamines PHDETA, HHTETA and HHTEPA were able to reduce the viscosity of L1316 crude oil to a maximum of 94.3%, 93.7% and 94.9%, respectively. The pour point of L401 crude oil could be greatly reduced by 3.1 °C, 3.3 °C and 3.4 °C with PHDETA, HHTETA and HHTEPA, respectively. The pour point of L1316 crude oil with PHDETA, HHTETA and HHTEPA was strongly decreased by 2.8 °C, 2.9 °C and 3.2 °C, respectively. Photomicrographs showed the co-crystallization of L401 and L1316 crude oil in the presence of PHDETA, resulting in the formation of a non-close-packed network of wax crystals. The multi-alkyl polyamines have multiple alkyl side chains that extend in different directions into the oil phase and can co-crystallize with the wax molecules, allowing the wax crystals to disperse.
To study the synergistic catalysis of an ex situ catalyst and in situ clay in the aquathermolysis of heavy oil, in this paper, a series of bentonite-supported catechol-metal complexes were prepared, and the catalytic viscosity reduction performance in the aquathermolysis of heavy oil was investigated. Under the optimized conditions, the viscosity can be reduced by 73%, and the pour point can be lowered by 15.0 °C at most, showing the synergistic catalysis of the ex situ catalyst and in situ clay in this aquathermolytic reaction. Thermogravimetry, physical adsorption-desorption, and scanning electron microscopy were conducted to characterize the thermal stability and microstructure of the ex situ catalyst. The components of the heavy oil before and after the reaction were fully characterized. Six model compounds were used to simulate the aquathermolysis reaction process. In order to study the mechanism of viscosity reduction after the catalytic aquathermolysis reaction, the compounds were analyzed by GC-MS. It is believed that these results will be beneficial in the future for related research in this field.
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