High-pressure Water Research Articles

Research on the Mechanism and Prediction Model of Pressure Drive Recovery in Low-Permeability Oil Reservoirs

China boasts significant reserves of low-permeability oil reservoirs, and the economic and efficient development of these reservoirs plays a crucial role in enhancing oil and gas production. However, the “difficult injection and difficult recovery” issue in low-permeability oil reservoirs is a major challenge. To address this, research is conducted on the mechanism of pressure drive based on the mathematical model of oil-water seepage in low-permeability reservoirs and the model of fracture permeability. The study finds that pressure drive technology, by directly delivering the pressure drive agent deep into the low-permeability reservoir, effectively prevents viscosity loss and adhesion retention of the agent in the near-wellbore area. This technology expands the swept volume, improves oil washing efficiency, replenishes formation energy, and facilitates the gathering and production of scattered remaining oil. For reservoirs with higher permeability, pressure drive yields quick results, and high-pressure water injection can be directly adopted for pressure drive to reduce costs. On the other hand, reservoirs with lower permeability have difficulty in water absorption, and the use of surfactant-based pressure drive can effectively reduce the seepage resistance of the reservoir, enhancing its water absorption capacity and improving development outcomes. Based on the mechanism of pressure drive development, further research is conducted on the production characteristics of pressure drive mines. Addressing the variability in pressure drive effects, big data analysis tools such as SHAP analysis and correlation analysis are employed to evaluate the main controlling factors of pressure drive in both new and old areas. Additionally, non-time series and time series pressure drive production forecasting models are established based on pressure drive data.

Numerical simulation of boiling dynamics in liquid Lead-Bismuth injected with multi-rupture high-pressure water jets

Once a steam generator tube rupture (SGTR) accident occurs in a lead-based fast reactor, it can trigger a domino effect of heat transfer tube ruptures, leading to a loss-of-flow accident involving multiple ruptures. This paper employs numerical methods to investigate the jet boiling phenomenon associated with the injection of sub-cooled water into high-temperature lead‑bismuth eutectic (LBE) through multiple nozzles. It explores how nozzle spacing, number, and diameter impact jet characteristics. Additionally, it analyzes flow characteristics and heat transfer mechanisms from the perspective of jet interaction. The study identifies critical areas within the multi-nozzle jet, specifically the three-phase mixing region, LBE entrainment region, water core region, and steam plume region. In scenarios where nozzle spacing is narrow or nozzle diameters differ significantly, the jet's base may undergo fragmentation. The jet process is categorized into two stages: the transition stage and the stable stage. During the stable stage, the mass flow rate of sub-cooled water remains relatively constant, with nozzle spacing exerting minimal influence on it. When considering the cross-sectional area of a single nozzle, an increase in nozzle diameter elevates the normalized mass flow rate, whereas the number and diameter of nozzles have little effect on it. Jet penetration depth is inversely related to nozzle spacing. As the number and diameter of nozzles increase, penetration depth initially rises and then decreases. Nozzle spacing has a minor influence on the jet's steam volume, while the number and diameter of nozzles are positively correlated with steam volume. Conversely, the number and diameter of nozzles negatively correlate with normalized steam volume.

The impact fretting corrosion behavior and damage mechanism of Inconel 690TT under different impact forces in high temperature pressurized water

The impact fretting corrosion of Inconel 690TT under different impact forces was investigated. The results indicated that there was a competitive relationship between formation of third body layer (TBL) and fragmentation of TBL caused by impact force. With the increase of impact forces, damage mechanism changed from adhesive wear to delamination wear, and crack initiation sites gradually shifted from TBL to internal oxidation zone in tribologically transformed structure (TTS) layer. Nanocrystalline boundaries and defects induced by impact force provided channels for internal oxidation. The formation mechanism of TTS was the combined effect of continuous dynamic recrystallization (cDRX) and twin-assisted cDRX.

A new tunnel drainage system using double-adhesive spray-applied membrane: key parameters and applicable scope

To address water leakage in tunnels with high water pressure, a new waterproof drainage system was proposed. The system uses a spray-applied material with double-adhesive properties as a waterproof layer, significantly reducing leakages, and incorporates a unique bottom drainage system to reduce water pressure. In order to check the effectiveness of the new drainage system and to analyze the effects of various structural measures on pressure reduction, a numerical seepage analysis was carried out under the conditions of a water head of 160 m and a surrounding rock permeability of 1 × 10−6 m/s. The results show that the maximum water pressure on the secondary lining is 0.6 MPa, which is about 60% reduction compared to a fully enclosed waterproof system and shows a significant pressure reduction. The spacing of the circumferential drainage pipe and the width of the drainage sheet significantly affect the drainage performance, while the arrangement of the drainage system and the size of the bottom drainage pipe have minimal impact. With full consideration of pressure reduction, cost efficiency and construction feasibility, it is recommended to use the following drainage scheme for iterative calculations during the design stage: “1” shaped arrangement, blind pipe diameter of 10 cm, width of drainage sheets of 0.8 m, and drainage spacing of 6 m. By combining the experimentally determined hydrostatic peel-off strength of 1.4 MPa for spray-applied membrane, the applicable scope of the new drainage system was acquired. The research results can provide valuable insights into the application of spray-applied waterproofing membrane in drainage tunnels with high water pressure.

Effects of coolant pH on crud deposition behavior on fuel cladding tube under subcooled nucleate boiling condition in high temperature pressurized water

The effects of coolant pH on the crud deposition behavior on the Zr alloy and the FeCrAl fuel cladding tubes under subcooled nucleate boiling condition were investigated. With the increase of coolant pH, the coverage rate and thickness of crud on the surfaces of both the Zr alloy and the FeCrAl fuel cladding tubes showed a decreasing trend. The solubility of crud compositions was reduced due to the increase of coolant pH, which resulted in the inhibition of the crud deposition process caused by SNB condition. Consequently, the elevated coolant pH value reduced the amount of crud on the surface of the fuel cladding tube.

Numerical Simulation and Critical Threshold Analysis of the Failure Process for Shield Tail Sealing System under High Water Pressure

Numerical Simulation and Critical Threshold Analysis of the Failure Process for Shield Tail Sealing System under High Water Pressure

A cGAN-based fatigue life prediction of 316 austenitic stainless steel in high-temperature and high-pressure water environments

The thermo-mechanical-chemical coupling effect presents significant challenges in accurately predicting the fatigue life of 316 austenitic stainless steel in high-temperature and high-pressure water environments (referred to hereafter as environmental fatigue). The complexity of environmental fatigue experiments results in limited and dispersed data, further making the life prediction difficult. Traditional fatigue life prediction models are often constrained by specific loading conditions and do not adequately account for the complex environmental influences. To address these issues, this paper proposes a novel environmental fatigue life prediction model of 316 stainless steel utilizing conditional Generative Adversarial Networks. The proposed model incorporates critical environmental factors, loading conditions and stacking fault energy, allowing direct prediction of environmental fatigue life. A comparative analysis on the predicted and experimental results reveals that the cGAN-based model significantly improves the prediction accuracy, reducing the fatigue life prediction error from a factor of 5 to within 3. To quantify the uncertainty in fatigue life prediction, the Monte Carlo Dropout method is employed to enable a probabilistic assessment of fatigue life. Furthermore, four environmental and loading conditions are established to evaluate the model’s extrapolation capability. The results demonstrate that the probabilistic fatigue assessment effectively captures data distribution and achieves high prediction accuracy.

Hydro-mechanical modeling of cohesive crack propagation of concrete lining in high internal pressure tunnels

High pressure tunnels with concrete lining have been extensively utilized in project practice. However, due to the characteristic of concrete being susceptible to cracking under tension, the lining inevitably develops cracks under high internal water pressure, posing a serious threat to the operation of tunnels. This study aims at developing a hydro-mechanical numerical model of cohesive crack propagation of concrete lining in high internal pressure tunnels. In this regard, the determination of cohesive element parameters is elucidated, the contact simulation within the software ABAQUS is improved to accurately characterize the interface between lining and surrounding rock, and the numerical calculation process in ABAQUS is realized using indirect coupled method. The simulation results align well with the physical model test and engineering monitoring data, demonstrating that the proposed method can accurately simulate the hydraulic interactions of high pressure tunnel. Additionally, a comparison with calculation models employing tie constraints to simulate the lining-surrounding rock interface is conducted. Finally, comparison with traditional continuum method reveals that while both methods exhibit consistent overall trends. It is recommended to choose the proposed method when describing the discontinuous propagation process of cracks, which cannot be simulated by the continuum analysis method.

Analysis of hydraulic breakdown and seepage of tail sealing system in shield tunnel machines

The use of shield method in tunnel construction is limited by the engineering conditions of highwater pressure. This is mainly due to the uncertainty of the pressure-bearing capacity of the sealing chambers of the shield tail under different grades and conditions when subjected to different external water pressures. Therefore, it is crucial to determine the pressure-bearing capacity of the sealing chambers. However, there is a lack of studies on the calculating method of the pressure-bearing capacity, which requires more theoretical investigation. To explore the common patterns of multi-grade sealing-related parameters and quantify the pressure-bearing capacity of the sealing chambers, a breakdown and leakage model of the shield tail is proposed, targeting the basic sealing unit of the system. Based on non-Newtonian fluid dynamics and fractal theory of porous media, the model is used to calculate the breakdown pressure and grease seepage rate corresponding to tunneling and shutdown states. In addition, a hydraulic breakdown device of the sealing unit of the static shield tail is built to investigate the relationship between the shield tail clearance and the shield tail brush porous media area, which helps to verify the theoretical model. Finally, the analysis of sealing chamber geometry parameters, grease rheological parameters, and an environmental parameter using the proposed theoretical model shows that the pressure-bearing capacity of the shield tail can be improved by increasing the shield tail clearance and grease yield stress. It also shows that the length of the sealing chamber and the plastic viscosity of the grease do not have a significant effect on the breakdown pressure of the shield tail. The model proposed in this paper will provide ideas for the calculation of the pressure-bearing capacity of multi-grade sealing chambers in the future.

Machine Learning-Assisted Prediction of Stress Corrosion Crack Growth Rate in Stainless Steel

Stainless-steel is extensively utilized in the key structural components of the main equipment in the nuclear island of pressurized water reactor nuclear power plants. The operational experience of nuclear power plants demonstrates that stress corrosion is one of the significant factors influencing the long-term safe operation of stainless steel in the high-temperature water of pressurized water reactor nuclear power plants. This study is based on the stress corrosion crack growth rate data of 316SS and 304SS stainless steel in the simulated primary water environment of pressurized water reactor nuclear power plants. Data mining and modeling were conducted using multiple machine learning algorithms, including Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Support Vector Regression (SVR), and Gaussian Process Regression (GPR), and the Sharpley Additive explanation (SHAP) method was employed to analyze the interpretability of the model. The results indicate that the stress corrosion crack growth rate prediction model based on XGBoost outperforms other models in all assessment indicators. Compared with empirical equations, XGBoost exhibits high flexibility and excellent data-driven learning capabilities. In the test set, 90% of the prediction errors are within the range of experimental values, with the maximum error multiple being 2.5, which significantly improves the prediction accuracy. Moreover, the distribution of SHAP values is consistent with the theoretical study of the stress corrosion behavior of stainless-steel, effectively reflecting the impact of cold working, temperature, and stress intensity factor on the stress corrosion crack growth rate, thereby proving the reliability of the model’s prediction results. The achievements of this study hold significant reference value and application prospects for the prediction of the stress corrosion behavior of stainless-steel in a high-temperature and high-pressure water environment of pressurized water reactor nuclear power plants.

Glacier Surges Controlled by the Close Interplay Between Subglacial Friction and Drainage

AbstractThe flow of glaciers and ice sheets is largely influenced by friction at the ice‐bed interface that can trigger rapid changes in glacier motion ranging from seasonal velocity variations to cyclic surge instabilities or even devastating glacier collapse. This wide range of transient glacier dynamics is currently not captured by models, and its implications for long‐term glacier evolution are uncertain. This highlights the need of developing improved descriptions for processes that occur at the glacier bed. Here, we present a model that describes the evolution of basal friction inspired by a “rate and state” approach, coupled to models of subglacial drainage and glacier flow, and investigate how these couplings affect the dynamics of glaciers. We show that a wide range of sliding behavior results from a feedback loop between subglacial drainage efficiency and friction which depends on the evolution of a frictional state that can be interpreted as the degree of cavitation or till porosity for hard and soft beds, respectively. In our simulations, we find that glaciers are susceptible to surging if they exhibit a transition to velocity weakening friction associated with a poor sensitivity of the drainage capacity to the frictional state. This potential materializes if the local topography and mass balance create the conditions for high water pressure to build up in an area sufficiently large to exceed a critical length. We advocate accounting for feedback loops between friction and drainage as a promising avenue for better understanding dynamical instabilities of glaciers and ice sheets.

Discrete element simulation of ground collapse induced by buried sewage pipeline breakage and soil leakage

The rupture of buried sewage pipelines constitutes a primary triggering factor of ground collapse. To investigate the phenomenon of ground collapse resulting from buried sewage pipeline breakage and soil particle leakage, numerical simulations employing the discrete element method (DEM) are utilized. The study focuses on examining the ground collapse mechanisms in both dry and water-rich sand stratum scenarios. A positive correlation is identified between the particle loss rate (PLR) and the magnitude of ground collapse, and a microscopic analysis of the mechanism of particle loss is carried out to visualize the soil arching process. The entire collapse process shows that the formation and destruction of soil arching are clearly accompanied by the particle loss phenomena. Additionally, the computational fluid dynamics (CFD) module is incorporated into the DEM to investigate the collapse of water-rich sand stratum. Parametric studies involving the burial depth of the pipeline, water pressure, the defect radius of the pipeline breakage, and the defect shapes are comprehensively conducted. It is found that the water pressure is the primary factor influencing the PLR, which progressively increases with higher water pressure, larger radius of pipe defect, and shallower burial depth.

Theoretical study on nonlinear seepage mechanism in fractal dendritic fracture network of low permeability coal with water injection

Coal seam water injection technology is adopted by many mines as an effective means of dust reduction in coal mines. There is a threshold pressure gradient phenomenon in the process of water injection in low permeability coal seam, which makes the flow of pressure water in the fracture structure of coal body present nonlinear seepage characteristics. To reveal the theoretical relationship between the structural parameters of coal and the nonlinear seepage characteristics, firstly, the Bingham fluid constitutive equation is used to describe the non-Newtonian behavior in low-permeability coal. Combined with the fractal tree-like bifurcation fracture network model, a mathematical analytical model of threshold pressure gradient is established. Secondly, the model was verified by high-pressure water invasion and radial seepage experiments, and the sensitivity of the model was analyzed. The results show that the error between the theoretical calculation value and the experimental measurement value is between 8.65 % and 42.4 %, which verifies the validity of the model. The above research results can provide a theoretical basis for improving the water injection effect of low permeability coal seam.

Experimental Study on Improving the Impermeability of Concrete under High-Pressure Water Environments Using a Polymer Coating

The concrete lining of high-pressure water conveyance tunnels permeates under high-pressure water. Dense and hydrophobic coating can effectively improve the impermeability of concrete. However, the coating exhibits varying impermeability in different high-pressure environments, which can even lead to coating detachment or damage. The objectives of this study are to improve the high-pressure impermeability of concrete by using a polymer coating, and to study the varying impermeability through experiments. This study applied a polymer coating called SCU-SD-SP-II (SSS) to concrete surfaces, and it formed a composite protective layer with an epoxy-modified silicone (EMS) coating. A series of high-pressure impermeability tests were conducted to study the seepage regulation of the coated concrete and the failure mechanism of the SSS coating under cracks in the concrete. The results indicate that the SSS coating has excellent impermeability. Pressurized water of 3 MPa could not permeate the SSS coating with a thickness of 0.5 mm within 24 h. Under both external and internal water pressure conditions, the SSS coatings improved concrete impermeability. Additionally, the average seepage height and relative permeability coefficient of the latter decreased by 49.6% and 71.2%, respectively, compared with the former. After concrete cracking, the SSS coating could withstand 3 MPa pressure on crack surfaces smaller than 1 mm. When the crack width was greater than 2 mm, the SSS coating deformed under 1 MPa pressure. As the pressure increased to 2 MPa or even 3 MPa, the SSS coating was punctured or torn due to stress concentration. This study provides new insights into the impermeability of concrete under high water pressure.

Experimental Investigation on Shear Strength at the Permeable Concrete–Fine-Grained Soil Interface for Slope Stabilization Using Deep Socket Counterfort Drains

In slopes where high pore water pressure exists, deep counterfort drains (also called drainage trenches or trench drains) represent one of the most effective methods for improving stability or mitigating landslide risks. In the cases of deep or very deep slip surfaces, this method represents the only possible intervention. Trench drains can be realized by using panels or secant piles filled with coarse granular material or permeable concrete. If the trenches are adequately “socket” into the stable ground (for example sufficiently below the sliding surface of a landslide or below the critical slip surface of marginally stable slopes) and the filling material has sufficient shear strength and stiffness, like porous concrete, there is a further increase in shear strength due to the “shear keys” effect. The increase in shear strength is due both to the intrinsic resistance of the concrete on the sliding surface and the resistance at the concrete–soil interface (on the lateral surface of the trench). The latter can be very significant in relation to the thickness of the sliding mass, the “socket depth”, and the spacing between the trenches. The increase in shear strength linked to the “shear keys effect” depends on the state of the porous concrete–soil interface. For silty–clayey base soils, it is very significant and is of the same order of magnitude as the increase in shear resistance linked to the permanent reduction on the slip surface in pore water pressure (draining effect). This paper presents the results of an experimental investigation on the shear strength at the porous interface of concrete and fine-grained soils and demonstrates the high significance and effectiveness of the “shear keys” effect.

Surface Topography Analysis of BK7 with Different Roughness Nozzles Using an Abrasive Water Jet.

This study investigated the effect of abrasive water jet (AWJ) kinematic parameters, such as jet traverse speed and water pressure, abrasive mass flow rate, and standoff distance on the surface of BK7. Nozzle A reinforced with a 100 nm particle-sized coating of titanium alloy has more wear resistance compared to Nozzle B coated with nothing. Through analysis of variance and measurement of BK7 surface quality, it is concluded that the grooving and plowing caused by abrasive particles and irregularities in the abrasive water jet machined surface with respect to traverse speed (3, 7.2, 7.8, and 9 mm/min), abrasive flow rate (7 L/min and 10 L/min, 80 mesh) and water pressure (2 and 3 MPa) were investigated using surface topography measurements. The surface roughness (15.734 nm) of BK7 results show that a nozzle coated with titanium alloy has more hardness, which protects BK7 undamaged and super-smooth. The values of selected surface roughness profile parameters-average roughness (Ra) and maximum height of PV (maximum depth of peak and valleys)-reveal a comparatively smooth BK7 surface in composites reinforced with 2% titanium alloy in the nozzle weight at a traverse speed of 7.8 mm/min. Moreover, abrasive water jet machining at high water pressure (3 MPa) produced better surface quality due to material removal and effective cleaning of lens fragmentation and abrasive particles from the polishing zone compared to a lower water pressure (2 MPa), low traverse speed (5 mm/min), and low abrasive mass flow rate (200 g/min).

Thermodynamic, economical and environmental performance evaluation of a 330 MW solar-aided coal-fired power plant located in Niger

The integration of solar thermal energy into a coal-fired power plant is one of the best ways to reduce the environmental impact of the latter linked to the release of carbon dioxide (CO2) into the atmosphere. In this paper, solar energy is used before the boiler, just after the first high-pressure feed water heater via a solar preheater (Water/Heat Transfer Fluid exchanger). It should be noted that in this study, there is no feed water heater displacement, and so the plant will operate in pure fuel-saving mode. To carry out an analysis of the integration of solar thermal energy in a coal-fired power plant, a 330 MW Solar Aided Coal Power Plant (SACPP) in northern Niger was studied. The results bring out that the annual solar energy production is 208 GWh, and solar energy can contribute up to approximately 15 % in the production of electricity. The considered SACPP significantly reduces the environmental impact of coal-fired power plants, leading to a reduction in CO2 emissions of around 381358 tons/year. In addition, the annual energy production cost from solar energy in the hybrid system is obtained as 0.0357 $/kWh and the investment payback period is around 12 months.

Criterion for hydraulic fracture propagation behaviour at coal measure composite reservoir interface based on energy release rate theory

In this study, a discriminative model of fracture expansion through a composite reservoir interface was established. During fracture transformation, the model, based on the theory of energy release rate at the fracture tip, helps clarify the critical conditions and assess the law of hydraulic fracture expansion through coal composite reservoir interfaces. This model considers shear and tensile processes during fracturing at the coal–rock interface and the effects of interface material property differences on fracture extension. In addition, fracture extension pattern differentiation is achieved by comparing the hydraulic fracture tip penetration and bending energy release rates (Gp/Gd) with the ratio of reservoir fracture and interface fracture energies (ΓR/ΓF). The accuracy of this discriminant criterion was verified by comparing the predicted results of the discriminant model with fracturing test results under identical conditions. The effects of various factors on Gp/Gd and hydraulic fracture penetration extension were investigated by using the sand-mudstone composite reservoir of the Shibox Formation in the Linxing Block, China, as the geological background. The results indicate that for certain values of ΓR/ΓF, Gp/Gd increases logarithmically with an increase in water pressure in the wellbore. Moreover, the difference in ground stress and elastic modulus between the layers exponentially increases with increasing Poisson’s ratio difference and the angle between fracture and interface and decreases logarithmically with increasing fracture height. These results indicate that hydraulic fractures are likely to penetrate from reservoirs with a high elastic modulus and Poisson’s ratio into reservoirs with a low elastic modulus and Poisson’s ratio. Furthermore, hydraulic fractures are likely to penetrate formations with large differences in pinch angle and ground stress. Under specific geological conditions, high water pressure in the wellbore and small seam height are favourable for fracture penetration.

Investigation on the Dynamic Characteristics of a New High-Pressure Water Hydraulic Flow Control Valve

Investigation on the Dynamic Characteristics of a New High-Pressure Water Hydraulic Flow Control Valve

Research and Application of Sealed coring Technology in In-situ Coal Seam of Directional Long borehole in Coal mine

In order to accurately obtain the gas content of in-situ coal seams in coal mines, a sealed coring technology for in-situ coal seams in coal mines has been proposed. By utilizing the pressure difference generated by high-pressure water at both ends of the piston, the piston is driven to cut off the positioning pin, which in turn drives the ball valve in the coring device to rotate, achieving the goal of cutting off and sealing the in-situ coal core. Performance tests were conducted on the sealing pressure of the coring device by opening the amount of water holes on the piston and using suspension pins of different materials, verifying the working parameters of the piston opening amount and suspension pins of different materials, providing basic data for subsequent industrial underground tests. Finally, during the industrial test underground, it was found that the gas content in the coal seam measured by closed sampling was 1.9-2.5 times higher than that of the coal seam sampled by the hole, which verified the successful design of the closed sampling device.