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.

In order to further improve the recovery of oil after binary composite flooding in offshore oil fields,based on the development contradiction existing after the binary flooding,combined with the indoor physical simulation experiment,three different combinations of oil displacement systems were designed on the basis of conventional oil displacement agents. According to the characteristics of the reservoir after the binary flooding,three kinds of high concentration polymer flooding,high concentration polymer + two yuan and heterogeneous phase were proposed and compared with the experiment. The results showed that the three experimental schemes showed different degrees of secondary decline in water,the shunt rate of the high permeability layer decreased,and the shunt rate of the medium and low permeability layer increased.The recovery rate of experiment was 13.55%,10.93% and 16.05%,respectively.It provides technical support for subsequent profile optimization and individual well personalized design,which lays the foundation for the completion of a set of recovery technology method system after a set of two yuan flooding.

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.

In order to realize the efficient development of the oilfield,it is needed to evaluate the productivity of the reservoir. According to the structure of horizontal well, the form of fracture and the distance of fracture, combined with the theory of seepage mechanics, a well test analysis model for multistage fractured horizontal wells considering wellbore storage and skin factor is established. A typical curve fitting chart of pressure and derivative is obtained, and a well testing interpretation software system based on the theoretical plate is developed. Based on the well test interpretation software system compiled by the theoretical plate, the IPR curve and the production decline curve are plotted by using multistage fracturing horizontal well test interpretation software.The results show that under the same production conditions, the influence of fracture distance and crack skin factor on productivity is less than the effect of crack half length on productivity. According to the curve of production flow rate with bottomhole flow at different production stages and the curve of output with production time at different bottomhole flow pressures, and the production capacity is predicted and evaluated at different stages of fracturing horizontal wells. It provides a strong guarantee for the efficient development of multistage fracturing horizontal wells.

The enhanced oil recovery technology of ASG (alkali, surfactant and nitrogen) composite foam and water alternating injection was studied in high temperature and high salinity low permeability reservoir. The ASG foam and water alternating injection experiments were carried out through indoor flooding experiments, and compared with water flooding nitrogen flooding and surfactant flooding. The results show that the enhanced oil recovery of the method adopted by this study is 16.61%, 10.26% and 9.21%, respectively, compared with water flooding, nitrogen flooding and surfactant flooding technology. Experimental study on injection parameters optimization of ASG foam and water alternating injection is carried out, and the parameters such as slug size, injection rate and gas fluid ratio of ASG composite foam are optimized by bench scale displacement test. The results show that under the condition of the same foam injection volume (1.2 times the pore volume), the effect of foam slug injection with 0.4 times pore volume is best. The foam injection rate has an optimum value of 1.5 mL/min. When the injection rate is too low, less foam is produced, gasliquid separation is easy to occur, and the blocking effect is poor. When the injection rate is too high, the size of the bubble is different, and it is easy to cause the bubble to merge, causing the bubble to burst, and at the same time, it is easy to cause the shear defoaming of the foam. When the gas fluid ratio is 3∶1, 2∶1 and 1.5∶1, respectively, the recovery rate is 2.04% higher than that of the single gas fluid ratio.

Passes temperature balance system of ethylene cracking furnace is a multivariable, nonlinear, strong coupling complicated process. Under the circumstances of multi-passes, the complexity and uncertainty of system could be increased by using difference control method. In view of the above problems, an improved difference control scheme was proposed, which processes all the passes as a whole. This scheme avoided employing the difference control technique reiteratively. The controller structure is simple and easy to be implemented. Simulation experiment shows that the improved difference control method is reasonable and has good tracking performance.