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Fracture-cavity carbonate reservoirs provide a large area, fracture development, high productivity, long stable production time, and other characteristics. However, after long-term exploitation, the lack of energy in the formation leads to a rapid decrease in production, and the water content in crude oil steadily increases, thereby disrupting normal production. To recover normal production, it is necessary to connect the cracks and pores that have not been affected during the original production, so as to allow the crude oil inside to enter the production cracks and replenish energy through methods such as hydraulic expansion of fracture-cavity carbonate rock. Accordingly, we propose hydraulic expansion techniques based on the following four processes for implementation: (1) applying high pressure to prevent a nearby fracture network from opening the seam, (2) connecting a distant fracture-cavity body, (3) breaking through the clay filling section of a natural fracture network, and (4) constructing an injection production well pattern for accelerating injection and producing diversion. Hydraulic fracturing involves closing or partially closing the original high-permeability channels, which usually produce a large amount of water, while opening previously unaffected areas through high pressure to increase crude oil production. We also introduce two composite techniques: (1) temporary plugging of the main deep fractures, followed by hydraulic expansion; and (2) capacity expansion and acidification/pressure processes. Hydraulic expansion allowed us to recover and supplement the formation energy and efficiently increase production. We tested various wells, achieving an effective hydraulic expansion rate of up to 85%. In addition, the productivity of conventional water injection and hydraulic expansion after on-site construction was compared for one well, clearly indicating the effectiveness of water injection and the remarkable crude oil increase after hydraulic expansion. [ABSTRACT FROM AUTHOR]

Fracture-cavity carbonate reservoirs provide a large area, fracture development, high productivity, long stable production time, and other characteristics. However, after long-term exploitation, the lack of energy in the formation leads to a rapid decrease in production, and the water content in crude oil steadily increases, thereby disrupting normal production. To recover normal production, it is necessary to connect the cracks and pores that have not been affected during the original production, so as to allow the crude oil inside to enter the production cracks and replenish energy through methods such as hydraulic expansion of fracture-cavity carbonate rock. Accordingly, we propose hydraulic expansion techniques based on the following four processes for implementation: (1) applying high pressure to prevent a nearby fracture network from opening the seam, (2) connecting a distant fracture-cavity body, (3) breaking through the clay filling section of a natural fracture network, and (4) constructing an injection production well pattern for accelerating injection and producing diversion. Hydraulic fracturing involves closing or partially closing the original high-permeability channels, which usually produce a large amount of water, while opening previously unaffected areas through high pressure to increase crude oil production. We also introduce two composite techniques: (1) temporary plugging of the main deep fractures, followed by hydraulic expansion; and (2) capacity expansion and acidification/pressure processes. Hydraulic expansion allowed us to recover and supplement the formation energy and efficiently increase production. We tested various wells, achieving an effective hydraulic expansion rate of up to 85%. In addition, the productivity of conventional water injection and hydraulic expansion after on-site construction was compared for one well, clearly indicating the effectiveness of water injection and the remarkable crude oil increase after hydraulic expansion.

Abstract Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts. This paper reports a hydraulic-forming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings. A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis. The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results. On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method, a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics. The effects of fluid characteristics, shaping pressure, axial feed rate, and friction coefficient on the wall thicknesses of torsions beams during formation were investigated. Fluid movement speed was related to tube deformation. Shaping pressure had a significant effect on rounded corners and straight edges. The axial feed speed was increased, and the uneven distribution of wall thicknesses was effectively improved. Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region, it had a significant influence on a large deformation of wall thickness in the V-shaped area. In this paper, a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.

Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts. This paper reports a hydraulic-forming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings. A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis. The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results. On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method, a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics. The effects of fluid characteristics, shaping pressure, axial feed rate, and friction coefficient on the wall thicknesses of torsions beams during formation were investigated. Fluid movement speed was related to tube deformation. Shaping pressure had a significant effect on rounded corners and straight edges. The axial feed speed was increased, and the uneven distribution of wall thicknesses was effectively improved. Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region, it had a significant influence on a large deformation of wall thickness in the V-shaped area. In this paper, a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam. [ABSTRACT FROM AUTHOR]

The design of hydro-bulge molds, able to provide hollow parts with special-shaped cross-sections, is still a pretty complicated task (especially for what concerns the design of the related hydraulic system and its “synchronization”). In the present work, this task is addressed through the introduction of a new type of overhead cylinder hydraulic synchronization system, able to correct automatically any deviation from the optimal process. Using the AMESim software, the displacement synchronization curve of the piston rods of the two cylinders is obtained and it is verified that the system is able to implement an automatic deviation correction function by adjusting the bidirectional servo valve. A mathematical model for the synchronization system is presented, and the transfer function of the closed-loop control system is determined accordingly. The results show that the system response is generated at about 0.1∼0.2 s with the system reaching an equilibrium state at about 0.2 s. [ABSTRACT FROM AUTHOR]

As a high expansion strength corresponds to a high heat transfer efficiency, this study investigated the expansion strength of an air-conditioning heat exchanger jointed by hydraulic expansion. A device that would be reliable and adaptable to different types of tubes and fins was designed and developed for testing hydraulic expansion. The device was used to perform a non-pulsating hydraulic expansion experiment on samples comprising tubes and fins to determine the hydraulic pressure range. The expansion strength was tested by performing tensile tests to evaluate the pull-out force at different bulging zones of the same sample with the selected hydraulic pressure. A series of pulsating hydraulic expansion experiments were performed on the joints of tubes and fins with different pulsating amplitudes and frequencies. Tensile tests were performed on the pulsating hydraulic expansion samples to study the influence of the pulsation parameters on the pull-out force. When the amplitude was fixed, an increase in frequency led to uniform expansion in the exchanger. This indicates that joint expansion in tubes and fins results in a more reliable heat exchanger performance. [ABSTRACT FROM AUTHOR]

As a high expansion strength corresponds to a high heat transfer efficiency, this study investigated the expansion strength of an air-conditioning heat exchanger jointed by hydraulic expansion. A device that would be reliable and adaptable to different types of tubes and fins was designed and developed for testing hydraulic expansion. The device was used to perform a non-pulsating hydraulic expansion experiment on samples comprising tubes and fins to determine the hydraulic pressure range. The expansion strength was tested by performing tensile tests to evaluate the pull-out force at different bulging zones of the same sample with the selected hydraulic pressure. A series of pulsating hydraulic expansion experiments were performed on the joints of tubes and fins with different pulsating amplitudes and frequencies. Tensile tests were performed on the pulsating hydraulic expansion samples to study the influence of the pulsation parameters on the pull-out force. When the amplitude was fixed, an increase in frequency led to uniform expansion in the exchanger. This indicates that joint expansion in tubes and fins results in a more reliable heat exchanger performance.

• It is the first time to systematically study and explore the failure cases of the accidental fracture of the hydraulic expansion mandrel of the tubesheet O-ring of the nuclear steam generator. • The stress corrosion behavior of the internal bulge defect on the inner wall of the heat transfer tube, which was caused by the fracture of the hydraulic expansion mandrel of the O-ring, was studied. • Characteristic zones of the fatigue fracture morphology were observed from the fracture area. The morphology could be divided into the fatigue source zone, the extension zone with brittle fracture and the transient fracture zone with plastic fracture. • The achievements of this paper could provide theoretical and practical support for preventing similar failure and ensuring the expansion quality of the steam generator tubes for nuclear power plants. Hydraulic expansion is commonly adopted for the tube to tubesheet expansion in the steam generator of nuclear power plants, and its quality greatly influences the stable and reliable operation of the steam generator. In this paper, an unexpected fracture of the hydraulic expansion mandrel occurred during the hydraulic expansion process, which caused the internal bulge defect (IBD) in the expanding area of the heat exchange tube. The corrosion test results showed that the IBD area had higher susceptibility to stress corrosion cracking (SCC) than the original tubes, which might lead to premature failure of the heat exchange tube in practical operation. To find out the root causes of this failure, the fracture morphologies of the hydraulic expansion mandrel were observed under the optical microscope (OM) and the scanning electron microscope (SEM), and the stress distribution during service were analyzed by mechanical calculation, The results indicated that the hydraulic expansion mandrel was repeatedly loaded by high-pressure medium during service, thus its weakest point was fractured due to high strain level and low cyclic number inelastic strain fatigue. Based on the results, the underlying mechanisms were discussed, and the countermeasures were proposed. The achievements of this paper provide theoretical and practical support for preventing similar failure and ensuring the expansion quality of the steam generator tubes for nuclear power plants. [ABSTRACT FROM AUTHOR]