During deepwater drilling, testing, production, or hydrate mining, the circulating medium in the wellbore may contain solid particles, such as rock chips and sand, in addition to drilling fluids, gas, and water. In the high-pressure, low-temperature conditions of deep water, gas intrusion can easily combine with free water in the drilling fluid to form hydrates, increasing the drilling risk. Therefore, understanding the formation patterns of hydrates in drilling fluids is of significant importance for the prevention and control of hydrates. This study utilized a small-scale high-pressure reactor to investigate the impact of the stirring rate, NaCl, and methanol additives, as well as the sand content on the hydrate formation process and gas consumption. The results indicate that the hydrate formation process can be divided into an induction stage, a rapid formation stage, and a slow formation stage. The induction stage and rapid formation stage durations are significantly reduced under stirring conditions. In NaCl and methanol solutions, hydrate formation is inhibited, with the induction stage duration increasing with higher concentrations of NaCl and methanol. There was no apparent rapid formation stage observed. The final gas consumption decreases substantially with increasing concentrations of NaCl and methanol, reaching no significant hydrate formation at a 20% concentration. The sand content has a significant impact on the slow formation stage, with the final gas consumption increasing within a certain range (in this work, at a sand content of 20%), and being notably higher than in the pure water system under the same conditions.

Safe and efficient deep drilling is a fundamental requirement for the development of oil and gas resources. In this regard, the application of membrane separation technology for drilling fluid gas separation and monitoring is highly significant. In this study, several commonly used permeable membrane materials were analyzed, and a PDMS separation membrane was preliminarily selected as a suitable material for downhole gas separation. We designed an experimental setup to investigate the separation performance of PDMS membranes. The effects of the separation pressure difference, operating temperature, and membrane thickness on the performance of PDMS membranes were analyzed, and the microstructure changes in the PDMS membrane under high temperature and pressure were observed using a scanning electron microscopy. The experimental results showed that PDMS membranes with a thickness of 150–200 μm can work stably and maintain good strength and permeability at a separation pressure difference of 1.1 MPa and a temperature of 150 °C. The SEM observations revealed that the PDMS separation membrane had a smooth surface and uniform microstructure after continuous operations for 15 h under the temperature and pressure conditions, without any cracks, demonstrating high temperature and pressure resistance. These research results provide an important reference for the application of PDMS separation membranes in downhole gas separation technology.