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Water-flooding reservoirs are the mainstay in developing mature oilfields in eastern China， and they have entered the ultra-high water cut stage as a whole after long-term water injection development. Laboratory studies and field practice show that there is still potential for significantly enhancing oil recovery. However， the difficulty of scientific and efficient development has increased due to the heterogeneity of reservoirs and development dynamics， and further research is needed to enhance oil recovery technology. Uncompartmentalized reservoirs face challenges such as severe extreme water consumption in the later stage of ultra-high water cut， affecting stable production and enhanced oil recovery through water flooding. Therefore， the theory of high water consumption zones was deepened， and the development technology of near-resistance layer recombination， the vector development technology of ultra-high water cut reservoirs， and the development technology of flow field adjustment in the later stage of ultra-high water cut were developed through innovation， achieving water consumption control and reduction， with an average oil recovery of 43.7%. In response to the characteristics of fault block reservoirs with numerous faults and small fault blocks， as well as the challenges of small remaining oil reserves and difficult exploitation during the ultra-high water-cut stage， understanding of the accumulation patterns of remaining oil and hydrodynamic regulation mechanisms was deepened. A series of leading development technologies were developed through innovation， such as artificial peripheral water flooding and stereoscopic development， improving reserve control and water flooding efficiency， with an average oil recovery of 29.4%. These technologies have supported the stable and profitable production of fault block reservoirs. Given the poor physical properties of low-permeability reservoirs and the difficulty of effective water flooding， nonlinear flow mechanisms and pressure flooding development mechanisms were researched， supporting development technologies were formed， and the development limits were constantly broadened. A series of differential development technologies have been innovated， such as water injection of simulated horizontal wells in ultra-low permeability reservoirs， well pattern adaptation for enhanced oil recovery in general low-permeability reservoirs， and pressure flooding in low-permeability and tight reservoirs， with an average oil recovery of 15.7%， realizing rapid and efficient development of low-permeability reservoirs. Through the above technical research， the efficient development of water-flooding reservoirs in ultra-high water cut stage is realized. According to the development characteristics and situation of different types of reservoirs， the directions for further enhancing oil recovery of water-flooding reservoirs are being put forward.

At the beginning of the 21st century，a large number of oil and gas wells were put into operation in Bohai E oilfield.With the production of the oilfield entering the middle and late stage，the phenomenon of annulus pressure is common in gas wells，severe situations may develop into same pressure of tubing and casing， causing serious pipe corrosion hazards and serious safety issues such as oil and gas leakage and environmental pollution.In order to ensure the production safety of old wells and break through the technical limitations in stimulation operation，in this paper the influence of different factors on the corrosion rate of oil and gas well tubing was investigated， the statistics on the operation of five gas wells in Bohai E oilfield were conducted， the types of media that might cause corrosion were discussed.The integrity of the oil casing body was tested using different methods.Based on indoor experimental results and actual conditions， the corrosion rate of the oil casing in the above five gas wells was predicted， which would provide a basis for determining the degree of oil casing corrosion.

Microbially induced carbonate precipitation (MICP) utilizing a urease active bioslurry is an ecofriendly method that can improve soil strength. However, the micromechanisms, such as ion diffusion, production rate of CaCO3 , porosity, and permeability of pile reinforced by bioslurry, require further investigation. In this study, both biopile model tests and a coupled fluid-flow, solute transport and biochemical reactive model were conducted to analyze the mechanical property and biocementation mechanism of pile formed by urease active bioslurry. Results showed that the simulated CaCO3 content along the biopile length after 120 h grouting was close to test results. The UCS of the biopile decreased from 3.44 MPa to 0.88 MPa and the CaCO3 content decreased from 13.5% to 9.1% with increasing depth. The largest reduction in CaCO3 content was observed in the middle part of the biopile as the CaCO3 crystals in the upper part hindered the downward transport of the cementation solution. The morphology of CaCO3 crystals was influenced by cementation solution concentration, as evidenced by the predominance of spherical vaterite crystals in the upper part of the biopile and rhomboidal calcite crystals in the middle and lower parts. During the grouting process, the concentration of calcium ions and urea decreased, while the ammonium ion levels increased with depth due to the utilization of calcium ions and urea for CaCO3 precipitation and ammonium ion production. The production rate of CaCO3 first increased rapidly to reach a peak value and then decreased. The porosity and permeability demonstrated both linear and nonlinear decreasing trends as the CaCO3 concentration increased. The largest reduction in porosity and permeability, reaching 20% and 58% in the biopile top. [ABSTRACT FROM AUTHOR]

The bevel cutting of large-thickness plates is a key process in modern industries. However, traditional processing method such as air-arc gouging bevel cutting or laser bevel cutting may cause serious deformation and rough surface quality due to the defects of the thermal cutting method. In order to improve the quality and efficiency of bevel processing, the abrasive waterjet cutting method is used in this research to overcome the challenge for bevel machining of high-strength DH40 steel plates with a large thickness. For different kinds of beveled structures, a 3D camera is used to measure the reference points defined on the workpiece and the SVD registration algorithm is adopted to transform the theoretical coordinate system to the actual coordinate system. Furthermore, the distance between the nozzle and the workpiece surface is also measured and compensated for to ensure the consistency of the bevel width. Finally, experiments are carried out for different kinds of bevels to verify the feasibility of the proposed method for high precision processing for beveled structures. The developed method has been effectively applied in the actual shipbuilding industry. [ABSTRACT FROM AUTHOR]