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Aiming at the current situation that the existing acidizing corrosion inhibitors are difficult to apply in high temperature, high concentration acid, and other complex conditions, this article uses nano-SiO2 as the core and preferably functional monomers to synthesize nano-SiO2@octadecylbisimidazoline quaternary ammonium salt (nano-SiO2@OBQA). Analytical methods such as nuclear magnetic resonance, infrared, and scanning electron microscopy were used for characterization. The corrosion inhibition performance of the N80 steel sheet by nano-SiO2@OBQA in 20% concentrated hydrochloric acid was studied using the high-temperature corrosion testing machine and adsorption isotherm model combined with quantum chemistry calculations to explore its mechanism of action. The results show that nano-SiO2@OBQA has good high-temperature resistance. When the temperature is 180℃ and the dosage of nano-SiO2@OBQA is 4%, the corrosion inhibition rate is 61.42 g·m−2·h−1. Studies have shown that the adsorption of nano-SiO2@OBQA on the surface of the N80 steel sheet follows the Langmuir isotherm adsorption model, which is spontaneous chemical adsorption.

In the weighting drilling fluid, barite will adsorb the free water and additives in the drilling fluid, which often worsens the performance of the drilling fluid. In order to optimize the performance of drilling fluid, a method for measuring the specific surface area of powder in liquid phase based on low field nuclear magnetic resonance (NMR) relaxation was established to study the occurrence state of barite in drilling fluid. The variation of specific surface area of barite in suspension with different concentrations were measured by particle size calculation and low field NMR, and the experimental results show that the specific surface area obtained by low field NMR can reflect the aggregation state of barite in liquid phase. Through organic carbon adsorption and rheological test, the adsorption law of barite to different drilling fluid additives was obtained. This study can solve the problem of additive addition in drilling fluid and optimize the performance of drilling fluid. [ABSTRACT FROM AUTHOR]

In the process of gas hydrate drilling, the drilling fluid is easy to intrude into the formation and change the formation temperature, pressure and chemical conditions of the hydrate formation, leading to the decomposition of hydrates in the surrounding formation and instability of the wellbore. The problem of wellbore instability caused by hydrate decomposition during hydrate drilling in the South China Sea is analyzed and studied. A composite phase change material is prepared by using intelligent temperature control method, adsorbing and modifying n-alkanes with vermicular graphite. The results show that the prepared composite phase change material has good phase change latent heat performance, the phase change temperature is controllable in the range of 17-18 °C, and the particle size can meet the basic requirements for effective recovery of screening particle size on site. It also has good compatibility with drilling fluid and is suitable for water-based drilling fluid system for hydrate reservoir drilling. [ABSTRACT FROM AUTHOR]

The deep Paleogene resources in the eastern part of the South China Sea have huge potential, but weathering crust and coal seams are often developed. The instability risk of coal seam, especially the interbedded coal slime well wall is high, and complex situations occur frequently during drilling and completion, which greatly hindering the exploration and development process. Aiming at the technical problems of borehole stability of complex coal seam of Paleogene in an oilfield in the eastern South China Sea, the mechanism of borehole instability is discussed through the analysis of the microstructure and mechanical properties of coal rock, and the technical countermeasures of "multiple cooperative" borehole stability drilling fluid based on "physical plugging-chemical consolidation-hydration inhibition" are put forward. An anti-collapsing drilling fluid formula suitable for complex coal seam of Paleogene in an oilfield in the eastern South China Sea is constructed. The evaluation results show that the drilling fluid formula has good rheology, fluid loss, lubrication, plugging and inhibition, excellent anti-pollution performance, and can improve the compressive strength of complex coal seam samples to a certain extent, which is conducive to the stability of complex coal seam wall, in line with the needs of field drilling engineering. [ABSTRACT FROM AUTHOR]