In order to understand the mechanism of CO₂ dissolved buried mechanism in high temperature and high pressure porous environment,physical simulation experiment was conducted to study CO₂ dissolved buried mechanism,mineralization buried mechanism and free buried mechanism in porous media by means of indoor physical model experiment.The results show that the solubility of CO₂ in formation water is mainly affected by temperature, pressure and salinity of formation water. CO₂ dissolved in formation water will mineralize with minerals in rocks, and the mineral content of rocks will change significantly before and after the reaction. The long core displacement experiment characterized the amount of free CO₂ storage and the oil displacement effect. The experiment reveal that CO₂ flooding in porous media has dual effects of burying and enhancing oil recovery.

Aiming at the problem of wax deposition in gas well exploitation of offshore HPHT gas reservoir, the gas?liquid?solid and fluid phase equilibrium theory and method of throttling effect principle was used to reveal the wax deposition mechanism of the abnormal high temperature and high pressure gas well, and it was found that wax deposition in high temperature and high pressure gas wells mainly occurs at the position of the oil nozzle where the temperature drops sharply when the wing valve of the gas well is closed. According to the phase equilibrium theory, the phase state of the original formation fluid in HPHT gas well was recovered and characterized, and the phase state change characteristics of gas?liquid?solid three?phase fluid, wax precipitation mechanism and process were described accurately. Based on the phase equilibrium model, the wax location, fluid composition change and the influencing factors of wax deposition were analyzed. It was reasonable to explain that the mechanism of wax precipitation in HPHT gas well is the transient phase transition from gaseous to liquid and then to solid due to the rapid change of temperature and pressure, and the corresponding prevention and control strategies are put forward.

Drainage continuity is very important for coalbed methane extraction. However, the well shut?in is unavoidable when draining. How to drain and draw up a reasonable drainage system after reopening the well are significant to increase gas production. Based on the analysis of coalbed methane production stage theory, combined with the field data about well shut?in, at the same time, numerical simulation method was used to study the change of reservoir parameters during well shut?in. The results show that well shut?in obviously changes the reservoir physical parameters,which causes the water saturation of the coal near the wellbore to increase, and the well bottom pressure increases. At the same time, it causes the re?adsorption of free gas near the wellbore and reduces the gas seepage capacity. Therefore, rapid drainage after reopening the well is helpful to dredge the flow channel of gas, improve gas flow capacity and increase gas production.