The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers. It has a significant effect on efficient development of unconventional reservoirs. First, based on the preferentially gas-covered ability and surface free energy changes, definition and evaluation methods have been established. Second, a method for altering rock wettability and its mechanisms have been studied, surface oriented phenomena of functional groups with low surface energy are the fundamental reason for gas wettability alteration of rock. Third, the effect of gas wettability on the surface energy, electrical properties and dilatability are investigated. Last, the effects of gas wettability on capillary pressure, oil/gas/water distribution and flow are investigated with capillary tubes and etched-glass network models. The gas wettability theory of reservoir rocks has been initially established, which provides theoretical support for the efficient production of unconventional reservoirs and has great significance.

To protect reservoir during drilling, the upper drilling fluid is generally converted into reservoir protection fluid by adding proper graded temporary plugging materials based on the average radius of pore throat in the reservoir, coupled with colloid filling particles. However, the fluid converted has a better temporary plugging effect on only some well sections because of the wide distribution of the average radius of pore throat in the reservoir. Aiming at present problems of reservoir protection drilling and completion fluid technology and reservoir characteristics such as strong heterogeneity, wide distribution of pore diameter, difficultly accurate prediction of pore diameter in reservoir, etc., a broad-spectrum oil-film fielding temporary plugging agent was developed with the oil-film method used for reservoir protection drilling. Completion fluid systems were established. The laboratory evaluation and field tests showed that there is good compatibility between the broad-spectrum oil-film fielding temporary plugging agent and common drilling fluid systems, as well, the plugging rate and recovery rate of cores treated by the developed systems are both over 90% and the field test skin factor is close to 0; thus, the developed systems have a better reservoir protection effect than conventional systems and can help to increase daily oil production.

After more than a century of development, drilling fluid technology has become capable of dealing with various extreme conditions. As the exploration and development targets shift towards complex oil and gas resources, however, the geological and surface conditions encountered get increasingly complex, which poses a greater challenge to drilling fluid. In this paper, bionics is introduced into the field of drilling fluids, imitating the characteristics, functions, structures, and principles of mussels and earthworms, and a bionic wall-fixing agent with side chains containing catechol functional groups to strengthen the wellbore is prepared. A bionic bonding lubricant that when making the direct friction between the two is changed to the sliding between the membranes is prepared. Compared with the advanced technology introduced from abroad, the strength of the rock is not only reduced but increased by more than 14%, the friction reduction rate is improved by 12.3%. Their mechanism of action and influencing factors are revealed from the macro and micro perspectives. Combined with the formation conditions encountered, other treatment agents are applied to develop a novel technology of bionic strengthened borehole and high lubricity water-based drilling fluid with comparable inhibition and lubricity to oil-based drilling fluid. In comparison with technology, the rate of well collapse is reduced by as much as 82.6%, the accident rate of stuck pipe is brought down by as much as 86.4%, the complication of stuck block is reduced by as much as 79.7%, and the overall cost is lowered by more than 30%. It is truly a safe, efficient, economic, environmentally friendly drilling fluid technology.

The instability of wellbore in hard and brittle shale formations is a key bottleneck constraining the safety and efficiency of drilling engineering. Traditional studies focused on drilling fluid density, particle plugging, and chemical inhibition; however, there is a lack of in-depth analysis on the precise control mechanism of wellbore stability by the rheological properties of drilling fluids. Specifically, while traditional methods are limited in addressing mechanical instability in hard brittle shales with pre-existing micro-fractures, rheological control offers a potential solution by influencing pressure transmission within these fractures. To address this research gap, this study aims to reveal the influence of drilling fluid rheological parameters (specifically viscosity and yield point) on the pressure transmission behavior of the micro-fracture network in hard and brittle shale and to clarify the intrinsic mechanism by which rheological properties stabilize the wellbore. Micro-structure analysis confirmed interconnected micro-fractures (0.5–30 μm). A micro-fracture flow model and simulations evaluated viscosity and yield point effects on pressure transmission. A higher viscosity significantly increased the pressure drop (ΔP) near the wellbore, with limited transmission distance effects. The yield point was minimal. The study reveals that optimizing rheology, particularly increasing viscosity, can suppress pore pressure, reduce collapse pressure, and improve stability. The findings support rheological parameter optimization for safer, economical drilling. In terms of rheological parameter optimization design, this study suggests emphasizing the increase in drilling fluid viscosity to effectively manage wellbore stability in hard brittle shale formations.

The corrosion mechanism of sixteen waterflood pipes of Nanbu Oilfield have been researched through a series of in-house experiments, and the dominant elements that cause the corrosion are revealed, the two elements are the hyper salinity and high corrosive ion content of the injected water quality. And the corrosive degree of every waterflood pipes are contrasted in the same condition, the technique measure that appropriate pipes are selected first and then adequate anti-corrosive agent are adapted is futher put forward. So the well control of corrosion of waterflood pipes can be realized, and there is an important instructing meaning for the production of Nanbu Oilfield.