Aiming at the problems of large amount of oilfield waterflooding technology, long measuring and adjusting period, low precision of measuring and measuring, and severe influence of well inclination, the mechanical stratified water injection technology is studied. The technology for the first time adopts hydraulic machinery style control, and integrates intelligent downhole monitoring, automatic tool control and other characteristics, to achieve a real⁃time monitoring, on⁃line measurement functions. The successful application of this technology in Well X6, an oil field in Bohai sea in June 2017 shows that the stratified water injection tool has reliable performance, on⁃line real⁃time measurement and adjustment, and improves the measuring and adjusting efficiency. It can be applied to acidizing operations, interwell tracer and other operations, and provides a new technical idea for stratified water injection development technology in Bohai oilfield.

Aiming at the demanding requirements of sealing performance in ultra⁃deep oil and gas wells, a double main sealing structure consisting of conical surface to conical surface and cylindrical surface to spherical surface was designed based on the special thread sealing mechanism. Using numerical simulation method, the changes of contact stress and the contact length of the sealing surface under the four conditions of tensile, compression, tension and internal pressure, tension and internal and external pressures were analyzed. The sealing performance of threaded joints under the ultimate load was studied, and the change rule of sealing capacity with different loads was obtained. The full⁃scale test results show that the sealing performance of the double main seal premium threaded joint meets the application requirements.

The two zones of water injection after X well repair in Bozhong 25⁃1 oilfield are confronted with two major problems. First, the injection pressure difference between two layers is 18 MPa, and secondly, the application of steel wire or coiled tubing is used to replace the horizon. The operation cycle is long and the cost is high. In order to solve the above problem, a new type of non⁃throwing fishing periodic water injection technology is applied, and the underground water injection level and water injection volume are adjusted by surface hydraulic control. The optimum design of sand control pipe string and water injection pipe string is matched to replace repeated steel wire operation. The problem has been solved, which guarantees the safety of water injection operation in high pressure differential layer, and saves 100% of the time and cost of steel wire allocation.

The southern part of Qinhuangdao 331 oil field is a heavy oil field which has not been exploited. The mode of thermal recovery is considered unusually in the early of exploitation. The design of thermal recovery mode depends on mass experimental data. Based on the indoor physical simulation, the influence of different noncondensate gas on high temperature and high pressure property of heavy oil is studied with a set of experiment instrument which support high temperature and high pressure. The results show that the volume ratio of CO ₂ dissolved in heavy oil of the southern part of Qinhuangdao 331 oil field is higher than N ₂ obviously, and the reduction rate of CO ₂ is 30%~90%. The lower temperature and greater pressure make CO ₂ reduce the viscosity of heavy oil more effectively. In different experiment temperature and pressure conditions, the N ₂ viscosity reducing extent is lower than 20%, and the dissolving capacity and viscosity reducing effect of flue gas is between N ₂ and CO ₂.