Shanjian Li

Subsequently, to improve the corrosion resistance of the coating, the surface of the PDA/FeSA ₃ -N80 steel coating was subjected to hydrophobic functionalization by introducing octadecanethiol (ODT), octadecylamine (ODA), and n-Dodecyltrimethoxysilane-modified silica (DTMS-SiO₂). The reconstruction effect of polydopamine (PDA) on the surface of the N80 steel sheet was confirmed through scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analyses. Subsequent electrochemical experiments showed that all hydrophobic coatings significantly improved the corrosion resistance of N80 steel in a 3.5% NaCl corrosive medium. After the three types of coatings were immersed in 3.5% NaCl solution for 30 days, the corrosion current density of the hydrophobic coatings was three orders of magnitude lower than that of the pure steel sheet, and the corrosion potentials were all more positive. Specifically, the current density of the DTMS-SiO₂/PDA/FeSA ₃ -N80 steel coating after 30 days of immersion was 5.6751×10⁻⁸ A/cm ² , that of the ODT/DA/FeSA ₃ -N80 steel coating was 6.3884×10⁻⁷ A/cm ² , and that of the ODA/PDA/FeSA ₃ -N80 steel coating was 6.3178×10⁻⁸ A/cm ² . Calculations showed that the corresponding corrosion resistance rates of the three coatings were 99.99%, 99.92%, and 99.97%, respectively. It can thus be confirmed that the three coatings have efficient corrosion resistance and service stability in NaCl corrosive medium, and can effectively slow down the corrosion process.

In order to solve the problems of long dissolution and preparation time, cumbersome preparation, and easy moisture absorption and deterioration during storage or transportation, acrylamide (AM), acrylic acid (AA), sodium p-styrene sulfonate (SSS), and cetyl dimethylallyl ammonium chloride (DMAAC-16) were selected as raw materials, and the emulsion thickener P(AM/AA/SSS), which can be instantly dissolved in water and rapidly thickened, was prepared by the reversed-phase emulsion polymerization method. DMAAC-16, the influence of emulsifier dosage, oil–water ratio, monomer molar ratio, monomer dosage, aqueous pH, initiator dosage, reaction temperature, reaction time, and other factors on the experiment was explored by a single-factor experiment, and the optimal process was determined as follows: the oil–water volume ratio was 0.4, the emulsifier dosage was 7% of the oil phase mass, the initiator dosage was 0.03% of the total mass of the reaction system, the reaction time was 4 h, the reaction temperature was 50 °C, the aqueous pH was 6.5, and the monomer dosage was 30% of the total mass of the reaction system (monomeric molar ratio n(AM):n(AA):n(SSS):n(DMAAC-16) = 79.2:20:0.5:0.3). X-ray diffraction analysis (XRD), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy analysis were carried out on the polymerization products. At the same time, a series of performance test experiments such as thickening performance, temperature and shear resistance, salt resistance, sand suspension performance, core damage performance, and fracturing fluid flowback fluid reuse were carried out to evaluate the comprehensive effect and efficiency of the synthetic products, and the results show that the P(AM/AA/SSS/DMAAC-16) polymer had excellent solubility and excellent properties such as temperature and shear resistance.

In this paper, the local corrosion inhibition effect of imidazoline on N80 oil pipeline steel in a NaCl-Na₂S solution was studied by the simulated blocking tank cell method, and the corrosion processes of the cathode and anode in the blocking zone were simulated. The blocking corrosion behavior of the pipeline tubing steel N80 in simulated corrosion solutions without and with different concentrations of an imidazoline corrosion inhibitor was studied by chemical analysis and electrochemical analysis. The results show that in the three solution systems, after the anode polarization of the occluded cell, the solution in the occluded region is acidified, the pH value decreases sharply, the migration of Cl⁻ and S²⁻ increases, and the concentration is increased in the blocked area. After adding the imidazoline corrosion inhibitor, the imidazoline inhibitor can reduce the migration of small-radius anions (Cl⁻ and S²⁻) to the occluded area, inhibit the acidification of the solution in the occluded area, and prevent the dissolution of metals in the occluded area. As a result, the corrosion of the occluded area is slowed down due to the change in the chemical and electrochemical state of the occluded area. In the three corrosion solution systems of 2% Na₂S + 5% NaCl, 2% Na₂S + 8% NaCl, and 2% Na₂S + 10% NaCl, the imidazoline corrosion inhibitor can form an adsorption film on the metal surface, thereby increasing the polarization resistance and decreasing the corrosion rate. The addition of an imidazoline corrosion inhibitor can significantly increase the kinetic constant of anode polarization, which can effectively inhibit the local corrosion of N80 steel in these corrosion systems.

In this study, based on existing heavy oil extraction technology, combined with the mineral composition in a reservoir, the synergistic catalytic effect of reservoir minerals and exogenous catalysts under the reaction system of a hydrogen-rich environment not only reduces the viscosity of thick oil but also reduces the extraction cost and further improves the recovery rate of heavy oil. In this study, the impacts of different reservoir minerals and exogenous catalysts on the aquathermolysis of heavy oil were investigated. The research results showed that the sodium montmorillonite within the reservoir minerals exhibited an optimal catalytic effect, and the synergistic catalytic effect of sodium montmorillonite and catalyst C-Fe (catechol iron) resulted in a viscosity reduction rate of 60.47%. Furthermore, the efficiency of different alcohols as hydrogen donors was screened, among which ethanol had the best catalytic effect. Under the optimal reaction conditions, the viscosity reduction rate after the addition of ethanol was 75.25%. Infrared spectroscopy, elemental analysis, thermogravimetry, and differential scanning calorimetry were used to study the changes in heavy oil before and after hydrothermal cracking. Element analysis showed that the synergistic catalytic effect of sodium-based montmorillonite and catalyst C-Fe increased the hydrocarbon ratio from 0.116 to 0.117, and the content of S and N elements decreased. This fully confirms the catalytic effect of sodium-based montmorillonite and C-Fe catalyst for he hydrogenation reaction of the unsaturated carbon in heavy oil.

Metal corrosion is becoming increasingly serious in oil and gas production, and one way to solve this problem is to modify the metal surface. Thus, a corrosion inhibition coating on the N80 steel was constructed via the self-polymerization and assembling of the dopamine. The optimum reaction condition of polydopamine films was determined by the corrosion rate assessment of the films coated N80 steel, which was the reaction at 60 °C and 5 g/L dopamine in the Tris-HCl buffer solution (pH = 8.5) for 1 h. The spectral results confirmed the existence of the polydopamine coating on the surface of N80 steel, and high stability of the coating in the oil well produced water was observed. The anti-corrosion performance of the polydopamine-coated N80 steel confirmed that high temperature accelerated the anti-corrosion effect of the coating, and the corrosion rate of N80 plate in 90 °C oil well produced water was 0.0591 mm·a⁻¹, lower than the standard value. The corrosion rates of the polydopamine coated N80, A3 and J55 plates at 90 °C were 0.0541 mm·a⁻¹, 0.0498 mm·a⁻¹ and 0.0455 mm·a⁻¹, respectively. No significant effects of the categories of corrosive medium and steel plate on the performance of the coating were observed.