In the dual-carbon context, how to economically, efficiently, and greenly enhance the recovery of heavy oil reservoirs by heavy oil recovery technology based on thermal recovery is a key concern of researchers. The essence of realizing commercial development of heavy oil reservoirs is to reduce the viscosity and enhance the flow capacity of heavy oil. The article systematically analyzed the viscosity-inducing mechanism of heavy oil and the viscosity-reducing mechanism of various viscosity reducers, summarized the synthesis processes of emulsifying viscosity reducers, oil-soluble viscosity reducers, and nano viscosity reducers, and evaluated the advantages and shortcomings of different viscosity reducers. The advantages and shortcomings of different viscosity reducers were evaluated. The development trend of viscosity reducers was also discussed and prospected. Sorting out the existing chemical viscosity reducers could help develop new viscosity reducer systems and enhance the recovery of heavy oil reservoirs.

Horizontal wells have obvious advantages in increasing the productioncapacity of oil and gas wells, but influenced by the non-homogeneity of the reservoir, the water breakthrough from horizontal wells is more common during the development of edge and bottom water reservoirs or water drive reservoirs, which brings great challenges to the efficient development of oil fields. Therefore, effective water detection and water plugging technology is one of the important means to improve the development effect of horizontal wells. To address the problem of difficult water breakthrough identification in horizontal wells, the characteristics and field applications of horizontal well water detection methods such as dynamic verification, mechanical water detection, water detection by logging and water detection with tracers were comprehensively summarized, and the problems and development directions of horizontal well water detection and water plugging methods were analyzed. This study can provide a reference for water detection and water plugging in high water-bearing inefficient horizontal wells.

In view of the shallow burial, high viscosity, and strong heterogeneity of crude oil in shallow super-heavy oil reservoir in Fengcheng Oilfield, there are many challenges in the SAGD development of dual-horizontal wells. This paper aims to study SAGD development technology and supporting technologies of shallow super-heavy oil reservoir, optimize the deployment design of double horizontal wells, design SAGD cycle preheating and reservoir project, and study supporting key technologies such as drilling and completion technologies, downhole string structure, and downhole temperature and pressure measurement. According to development practice and technical and economic indicators, the technical limits of SAGD development for super-heavy oil dual-horizontal wells were formulated, and new technologies to improve SAGD development effects were comprehensively discussed, including composite well pattern development, reservoir expansion and stimulation, and solvent-assisted SAGD. The supporting technologies for shallow SAGD series development provide an important reference for the development of similar gas reservoirs.

It is difficult to achieve economic and efficient development of unconventional resources by conventional fracturing technologies which only make single symmetric fractures due to extremely low permeability, so it is necessary to forcibly expand the stimulated reservoir volume by fracturing and make the fracture network more developed to enhance the produce of a single well. Temporary plugging is an effective method to improve fracture complexity. In this paper, a summarization was conducted on the existing studies and application effects of temporary plugging balls, conventional temporary plugging agents, fiber temporary plugging agents and other new synthetic temporary plugging agents used in the fracturing stimulation of unconventional reservoirs such as shale at home and abroad. Moreover, applicable conditions, advantages and disadvantages of the temporary plugging agents were explained, and the future development of temporary plugging agents was also stated clearly. The study results provide a significant reference and guidance for the studies on temporary plugging agents for fracturing stimulation of unconventional reservoirs in the future.

To improve the development effect of oil wells after fracturing in tight reservoirs, based on the Block ZD of Henan Oilfield, the permeability-stress sensitivity relationship of matrix and fracture was determined by fracture-variable-conductivity physical experiments, and the numerical simulation was applied, to determine the optimal values of CO₂ huff-n-puff parameters in different reservoirs of tight oil reservoirs. The result shows that in the injection and shut-in stages, the affected area of CO₂ is getting wider and wider, the crude oil viscosity in the affected area decreases significantly, and the CO₂ is produced with the crude oil in the production stage, and the range of production is larger; the oil exchange rate increases and then decreases with the increase of CO₂ injection volume or shut-in time, which is positively correlated with the CO₂ injection rate and negatively correlated with the huff-n-puff period; the better the reservoir physical properties, the lower the optimal CO₂ injection volume and injection rate, and the shorter the optimal shut-in time and the longer huff-n-puff cycles. The CO₂ huff-n-puff test was carried out in Well ZA4121 in four types of reservoirs, and the accumulated oil increment was 303.4 t, which achieved a good development effect with an oil exchange rate of 0.16 t/t. The research results can provide reference for the study and application related to CO₂ huff-n-puff after fracturing in tight reservoirs.