Slurry Rate Research Articles

Numerical Simulation and Experimental Investigation of Rotating Blade Centrifugal Jet in Slurry Blast Device Used for Steel Strip Descaling

Under the requirement of clean production, a new type of slurry blast device for mechanically removing oxide scale on the surface of steel strips is presented, which can avoid the serious problems of rapid wear, low service life, and low efficiency of the traditional abrasive water jet with a nozzle. In this paper, the numerical simulation of the rotating blade centrifugal jet in the slurry blast device is conducted based on CFD, where the DPM and the erosion model are innovatively employed to simulate the movement characteristics of abrasive particles and the erosion rate of mixed slurry on the surface of the steel strip. Simulation results show that the erosion rate and particle motion velocity are proportional to the blade rotation speed and inlet pressure. Reasonable inlet pressure and rotation speed are helpful for improving the rust removal efficiency of slurry blast devices. An experimental system is established to validate the simulation results. The experimental results are consistent with the simulation trend, which exhibits that the developed slurry blast device is feasible for steel strip descaling. This work will play substantial guiding roles in the engineering optimization of slurry blast devices for steel strip descaling.

Predictive and experimental research on the polishing slurry consumption model for ultrasonic vibration-assisted polishing of optical glass BK7

In the actual production process, people usually focus on the machining accuracy and machining efficiency, ignoring the production costs and environmental problems caused by the excessive amount of polishing slurry. Polishing slurry plays an important role during the ultra-precision polishing process, which is often overused so that better surface quality being obtained. However, when the amount of polishing slurry exceeds a threshold, the surface quality would not be significantly improved. Meanwhile, excess polishing slurry can cause environmental pollution and unnecessary waste. In this paper, a new calculation method was proposed, and a novel predictive model of polishing slurry consumption was established to calculate the consumption of polishing slurry in the deterministic polishing. Ultrasonic atomization (UA) was introduced into ultrasonic vibration-assisted polishing (UVAP), and the effects of UA on material removal mechanism (MRM) have taken into consideration. The effect of different machining parameters on the amount of polishing slurry was analyzed. Subsequently, a series of experiments were carried out under three different the flow rate of the polishing slurry (small, appropriate, and excessive) with various ultrasonic amplitudes. The experimental results indicate that the amount of polishing slurry in the deterministic polishing can be accurately calculated by the proposed model, and the maximum consumption of polishing slurry can be reduced by 22.17%. The predictive model of the flow rate of polishing slurry fills the gap and it contributes to the realization of green production, which is an important guidance for the actual production.

Preparation of active MgO composite expansive agent and its effect on volume deformation performance of cement slurry during hydration

ABSTRACT The serious volume shrinkage of G-grade oil well cement during the hydration period and the initial stage of hardening will cause poor cementing quality at the first and second cementing interfaces, which will lead to annulus channeling and ultimately affect the normal production of the oil well. Therefore, we researched high-activity MgO composite expansive agent. By calcination of industrial MgO at different temperatures and then rapid cooling, we obtained MgO with different activities. We then analyzed the reactivity and microstructure of these samples and tested their effects on the volume shrinkage of cement slurry in the early stage of hydration. The experimental results showed that the activity of the sample calcined at 800°C for 1 hour then cooled rapidly is more suitable. After adding the expansive agent, the volume shrinkage rate of cement slurry can be minimized to only 0.95% after 10 hours, while the volume shrinkage rate of blank cement slurry can reach 4.02% after 10 hours. By compounding the calcined active MgO with CaO and UEA, the composite expansive agent M-AC is obtained. The evaluation results showed that M-AC expansive agent can make up for the insufficient expansion of cement after hardening, realize the volume shrinkage compensation of cement in the whole process of cementing, and improve the cementing quality.

Experiment and Numerical Simulation on Grouting Reinforcement Parameters of Ultra-Shallow Buried Double-Arch Tunnel

For an ultra-shallow buried double-arch tunnel with a large cross-section, the arching effect is difficult to form in surrounding rock, and grouting method is often adopted to reinforce the surrounding rock. Hence, examining the grouting reinforcement parameters is of great significance for potential failure and collapse prevention. The land part of Haicang undersea tunnel was selected as a case study; laboratory experiments, theoretical analysis, and numerical simulation were performed to determine the grouting solid strength and grouting reinforcement parameters. The effects of different water–cement ratios on slurry fluidity, setting time, bleeding rate, and sample strength were studied by laboratory experiments. A method was proposed to determine the shear strength parameters of grouted surrounding rock through the grout water–cement ratio and the unconfined compressive strength of the rock mass. Numerical simulations were performed for grouting reinforcement layer thickness and the water–cement ratios. The deformation and stability law of tunnel surrounding rock and its influence on surrounding underground pipelines were obtained considering the spatial effect of tunnel excavation and grouting reinforcement. The reasonable selection range of grouting reinforcement parameters was proposed. The initial setting time and bleeding rate of cement slurry increased with the increasing water–cement ratio, while the viscosity of cement slurry and sample strength decreased with the increasing water–cement ratio. The shear strength parameters of grouted surrounding rock were determined by the water–cement ratio of grout and unconfined compressive strength of rock mass before grouting. When the thickness of grouting reinforcement layer h = 1.5 m and the water–cement ratio of grout was suggested η = 0.85, the surface settlement, the deformation of the vault, and the deformation of the nearby pipeline all met the design. Moreover, the construction requirements were more economical. Research results can provide a reference for the selection of grouting reinforcement parameters for similar projects.

Post‐Wildfire Generation of Debris‐Flow Slurry by Rill Erosion on Colluvial Hillslopes

AbstractLandscapes after wildfire commonly experience accelerated hillslope erosion, which often contributes to the mobilization and volume of debris flows. However, quantitative studies of the erosion and its relationship to rainfall, runoff, and landscape characteristics have been limited to a narrow range of physiographic conditions. We estimated the volume and delivery rate of slurry (a water‐sediment mixture) supplied to stream channels during a post‐wildfire rainstorm that generated large debris flows in six catchments above Montecito, CA, in 2018. We mapped the distribution of rills and measured their cross‐sectional geometries to quantify the influences of runoff, lithology, and hillslope characteristics on the sediment volumes released by rill erosion, and we scaled the results up to the 19.5 km2 of burned hillslopes in the source catchments. We computed the likely rate of surface runoff during the rainstorm and developed an empirical model for the evolution of a representative hillslope‐spanning rill to illustrate the magnitude and speed of the erosion process. Rilling was the dominant form of erosion across the hillslopes of the source catchments, and the rapid evacuation and mixing of water and sediment during rill formation supplied a slurry with high solids concentrations to stream channels. Colluvium on shale formations was more continuous, finer‐grained, and probably less permeable than colluvium on sandstones, and these differences affected the extent and dimensions of rills. As a result, shale hillslopes were the dominant source of slurry to the debris flows and supplied over twice as much slurry per unit burn area as sandstones.

Modeling and analysis of the material removal rate for ultrasonic vibration–assisted polishing of optical glass BK7

The emergence of ultrasonic vibration–assisted polishing technology has effectively improved the machining accuracy and efficiency of hard and brittle materials in the modern optical industry; however, the material removal mechanism of ultrasonic vibration–assisted polishing (UVAP) still needs to be further revealed. This paper focuses on the material removal mechanism of ultrasonic vibration–assisted polishing of optical glass (BK7), the application of ultrasonic to axial vibration, and the atomization of the polishing slurry; the material removal model was established. Based on the analysis of the relationship between the nominal distance d of the polishing pad and the actual contact area distribution, the prediction of the material removal profile is realized. In addition, the effects of different parameters on the material removal rate (MRR) were analyzed, including polishing force, spindle speed, abrasive particle size, ultrasonic amplitude, feed rate, and flow rate of polishing slurry. Based on the motion equation of abrasive particles, the trajectory of abrasive particles in the polishing slurry was simulated, and the simulation results show that the introduction of the ultrasonic vibration field changes the motion state and trajectory of embedded and free abrasive particles. The new model cannot only qualitatively analyze the influence of different process parameters on MRR, but also predict the material removal depth and MRR, providing a possibility for deterministic material removal and a theoretical basis for subsequent polishing of complex curved surfaces of optical glass.

Preparation of Slow-Release Insecticides from Biogas Slurry: Effectiveness of Ion Exchange Resin in the Adsorption and Release of Ammonia Nitrogen

The insecticidal ingredient in a biogas solution being fully utilized by cation exchange resin to produce slow-release insecticide is of great social value. In this work, the feasibility of ammonia nitrogen in a biogas slurry loaded on resin as a slow-release insecticide was evaluated by studying the effect of adsorption and the slow release of ammonia nitrogen by resin. The effects of the ammonia nitrogen concentration, resin dosage, adsorption time and pH value on the ammonia nitrogen adsorption by the resin were studied. The results showed that the ion exchange resin had a good adsorption effect on the ammonia nitrogen. With the increase of the resin dosage, time and ammonia nitrogen concentration, the adsorption capacity increased at first and then stabilized. The ammonia nitrogen adsorption capacity reached its maximum value (1.13 mg) when the pH value was 7. The adsorption process can be fitted well by the Langmuir isothermal adsorption equation and quasi-second-order kinetic model. Additionally, the release rate of the ammonia nitrogen increased with the increasing sodium chloride concentration. The adsorption capacity of ammonia nitrogen by the D113 (resin type) resin decreased by 15.8% compared with the ammonium chloride solution. The report shows that the ion exchange resin has a good adsorption effect on ammonia nitrogen, which is of guiding significance for expanding the raw materials for slow-release insecticides, improving the utilization rate of biogas slurry and cleaner production of slow-release insecticides from biogas slurry. Additionally, all variables showed statistical differences (p < 0.05).

Incapability of biochar to mitigate biogas slurry induced N2O emissions: Field investigations after 7 years of biochar application in a poplar plantation

Nitrous oxide (N2O) is a potent atmospheric greenhouse gas that is largely emitted from soils due to the enhanced use of reactive nitrogen in agriculture and plantations. In this study, we evaluated the N2O mitigation ability of biochar after 7 years of application in a poplar plantation. The field experiment was based on combinations of three biochar (0, 80, and 120 t ha−1) and four biogas slurry (0, 125, 250, and 375 m3 ha−1) rates following a factorial design. N2O flux rates were measured for seven consecutive months using in situ static chambers. Soil physicochemical characteristics, potential nitrification rate (PNR), denitrification (DEA), and N2O reduction were recorded once each in September 2019 and January 2020 via lab incubations. In addition, qPCR assays were used to assess the abundance of key nitrifying and denitrifying functional genes. Biochar application after 7 years had no significant effects on N2O flux rates, PNR, and DEA rates. However, a triggering effect of biogas slurry on soil N2O emission was observed, although there was no correlation between biogas slurry rates and N2O emission rates. Factorial ANOVA showed a significant effect of biogas slurry and its interaction with biochar on the relative abundance of bacterial denitrifying and nitrifying functional genes. Additionally, significant correlations of N2O emission rates with PNR rates and NO3− concentration indicated that nitrification was the dominant pathway of N2O emission. Thus, a single biochar application did not mitigate N2O emission rates induced by biogas slurry on a long-term scale.

Study of a Polyamine Inhibitor Used for Shale Water-Based Drilling Fluid.

Here, we report a water-soluble shale inhibitor for inhibiting shale hydrate formation. The copolymer denoted as thermogravimetric analysis (TGA) was synthesized via triethanolamine, two maleic anhydrides, and glacial acetic acid. The infrared (IR) and gas chromatography (GC) results indicated that TGA is a low molecular weight polymer inhibitor (IR) and is the most commonly used method to identify compounds and molecular structures qualitatively. It is mainly used to study the molecular structure of organic substances and conduct qualitative and quantitative analyses of organic compounds. The main function of GC is for polymer molecular weight analysis. With the aid of shale rolling recovery experiments, particle size distribution experiments, triaxial stress experiment methods, bentonite slurry rate inhibition experiments, and thermogravimetric experiments to evaluate TGA inhibition characteristics, the inhibition effect of TGA is better than that of the traditional inorganic salt inhibitor KCl, polymer amine inhibitor UHIB, and organic cationic shale inhibitor NW-1. When the mass fraction is 0.2%, the cutting recovery rate increases from 18.3 to 94.1%. The compressive strength of the shale core after adding 1% TGA inhibitor is 177.9 MPa, which is close to the original core compressive strength of 186.5. The wet sodium montmorillonite crystal layer spacing after treatment with 0.5%, 1.5%, and 3% TGA aqueous solution is 1.38, 1.35, and 1.35 nm, respectively, and the sodium montmorillonite crystal layer spacing after diesel treatment is 1.34 nm, indicating that the inhibitory effect of TGA on sodium montmorillonite is equivalent to that of diesel and that TGA can effectively inhibit the hydration and dispersion of sodium montmorillonite. At the same time, the crystal layer spacing and the weight loss rate of sodium montmorillonite modified by TGA inhibitors did not change significantly after adsorption of deionized water, which proved that TGA inhibitors could be adsorbed in the crystal layer space of sodium montmorillonite to inhibit hydration and dispersion of sodium montmorillonite. Field test results show that TGA can significantly improve the inhibition performance of the field drilling fluid, and the effect is better than the strong conventional inhibition water-based drilling fluid system, which solves the problems of wellbore instability and considerable friction in horizontal shale sections and provides a new idea and method for efficient shale gas drilling.

Numerical investigation of flow control technology for grouting and blocking of flowing water in karst conduits

AbstractA sequential flow and solidification method was applied to the numerical investigation of flow control technology for grouting and blocking of flowing water in karst conduits. This method accounted for the temporal‐ and spatial‐evolution characteristics of the viscosity. It achieved the visualization of grouting in flowing water in a conduit, and was used to explore a reasonable and effective method for grouting through flow‐control technology. Firstly, the responses of different water tables and flow‐control intensities were studied by establishing a generalized model of flow control at the outlet of a conduit. Secondly, the initial sedimentation location and the distance of down‐flow and counter‐flow of slurries with different intensities of flow control were compared and analyzed. The outlet flow, the loss rate of the slurry, and the distribution laws of velocity and pressure inside the conduit during plugging were further analyzed. In addition, the mechanism of flow control for the grouting and plugging of large‐flow conduits was revealed. The results showed that the most direct effect of flow control on grouting was to decrease the flow rate of flowing water, and the most essential role was to improve the retention rate of slurry. Moreover, the results were applied to the large‐scale water inrush control project of Hejing Limestone Mine, China. The slurry stop devices improved the retention rate of slurry and optimized the grouting technology, which had a certain guiding significance in the treatment of water‐inrush disasters in karst areas.

Thermal control effects and mechanism of slag and fly ash on heat development of cement slurry used in hydrate formation

Based on the requirements of low hydration heat and temperature rise of cement slurry used in deep-water gas hydrate formation, the thermal control effects of slag and fly ash on heat development of cement slurry were quantitatively and qualitatively investigated. The results show that the temperature rise, hydration heat and heat release rate of cement slurry were successfully reduced by slag and fly ash, which is beneficial to the cementing of gas hydrate formation, the engineering accidents, such as enlarged diameter, were avoided. Compared with pure cement slurry, the temperature rise of sample PCF37.5% and PCS37.5% was reduced by 16.5 and 12.1 °C, respectively. The hydration heat of sample PCF37.5% and PCS37.5% at 48 h was reduced by 35.3 and 16.3%, respectively. Secondly, the thermal control mechanisms of slag and fly ash on heat development of cement slurry were studied by X-ray Diffraction, Scanning Electron Microscope and Low Field Nuclear Magnetic Resonance Testing. As a result, the quantitative analysis shows that the heat development of cement slurry was controlled firstly by the lower hydration heat characteristics of slag and fly ash. The hydration heat of slag and fly ash at 48 h is 28.153–47.067 J/g and 2.0549–4.765 J/g, respectively. Besides, the qualitative analysis of hydration process and products shows that the heat development was also controlled by delay effect of slag and fly ash. Compared with pure cement slurry, the hydration products of sample PCF50.0% and PCS50.0% were obviously reduced. The innovation of this study is that the fly ash and slag were used to control the heat development of cement slurry used in hydrate formation. Especially, the control mechanisms were obtained quantitative calculation and qualitative analysis. Furthermore, the research results could provide technical reference for the design of cement slurry for hydrate formation cementing.

Experimental Study on Fluid Properties of Cement-Fly Ash Slurry Subjected to Multifactors

There are many factors affecting the characteristics of cement-fly ash slurry in practical engineering. Thus, this paper studies the influence of multifactors on the fluid properties of cement-fly ash slurry based on water-cement ratio ( w / c ) (0.75, 1, 1.25, and 1.5), fly ash content (0%, 10%, 20%, 30%, 40%, and 50%) and temperature (20°C, 40°C, 60°C, and 80°C). The bleeding ratio, initial setting time, final setting time, and viscosity were analyzed under coupling conditions. It is found that the water-cement ratio ( w / c ) is the main factor that affects the rheological properties and bleeding rate of slurry. The temperature affects the stability of the slurry in terms that the bleeding ratio of the slurry decreases as the temperature increases. The addition of fly ash enhances the stability of the slurry under different temperature conditions.

Potential of Maritime Transport for Ocean Liming and Atmospheric CO2 Removal

Proposals to increase ocean alkalinity may make an important contribution to meeting climate change net emission targets, while also helping to ameliorate the effects of ocean acidification. However, the practical feasibility of spreading large amounts of alkaline materials in the seawater is poorly understood. In this study, the potential of discharging calcium hydroxide (slaked lime, SL) using existing maritime transport is evaluated, at the global scale and for the Mediterranean Sea. The potential discharge of SL from existing vessels depends on many factors, mainly their number and load capacity, the distance traveled along the route, the frequency of reloading, and the discharge rate. The latter may be constrained by the localized pH increase in the wake of the ship, which could be detrimental for marine ecosystems. Based on maritime traffic data from the International Maritime Organization for bulk carriers and container ships, and assuming low discharge rates and 15% of the deadweight capacity dedicated for SL transport, the maximum SL potential discharge from all active vessels worldwide is estimated to be between 1.7 and 4.0 Gt/year. For the Mediterranean Sea, based on detailed maritime traffic data, a potential discharge of about 186 Mt/year is estimated. The discharge using a fleet of 1,000 new dedicated ships has also been discussed, with a potential distribution of 1.3 Gt/year. Using average literature values of CO2 removal per unit of SL added to the sea, the global potential of CO2 removal from SL discharge by existing or new ships is estimated at several Gt/year, depending on the discharge rate. Since the potential impacts of SL discharge on the marine environment in the ships' wake limits the rate at which SL can be applied, an overview of methodologies for the assessment of SL concentration in the wake of the ships is presented. A first assessment performed with a three-dimensional non-reactive and a one-dimensional reactive fluid dynamic model simulating the shrinking of particle radii, shows that low discharge rates of a SL slurry lead to pH variations of about 1 unit for a duration of just a few minutes.

Effect of Different Activators on Rheological and Strength Properties of Fly Ash-Based Filling Cementitious Materials

In this paper, lime, gypsum, NaOH, and Na2SO4 are mainly used to study the activation degree and activation mechanism of fly ash, and L9 (34) orthogonal table is used for the orthogonal test. The influence of different activators on the rheological and strength properties of slurry was analyzed. The microstructure and hydration products of fly ash cement cementitious body were studied by SEM and XRD. The results show that the bleeding rate of slurry containing activator fly ash system is between 2.24% and 3.37%, which is much higher than that of pure cement slurry (9.25%). Therefore, the addition of this system can improve the fluidity of slurry, and the optimal scheme is a3b2c2d2. The results show that the compressive strength of cement with activator fly ash system is much lower than that of pure cement, but the increase of strength is between 31% and 85%, which is much greater than that of pure cement (35%–46%). The optimal scheme is A2B2C3D3 or A3B2C3D3 at 3 days and A1B3C2D3 at 28 days. According to the scanning results of SEM and XRD, the addition of activator can significantly improve the hydration degree of fly ash and form a more complex network structure without obvious gap.

Experimental investigation on the enhanced performance of a solar PVT system using micro-encapsulated PCMs

In a photovoltaic–thermal (PVT) solar collector, a small percentage of the absorbed solar radiation can be converted into electricity and the rest become heat. The heat could be collected through various working mediums. It is of great practical significance to study PVT system and improve its performance further. In this study, an experimental PVT system using MPCM (Microencapsulated Phase Change Material) slurry as the cooling medium was designed and established. The comprehensive performance of the PVT system was studied. The measured electrical and thermal efficiency of the PVT system using MPCM slurry or tap water under various conditions were compared. Moreover, the MPCM slurry was also used as the working fluid in an outdoor PVT system. The practical performance was compared with those of a traditional water-cooled PVT system and a similar system with PCM layer. The results showed that increasing the flow rates of the MPCM slurry could reduce the temperature of PV cell and improve the thermal and electrical efficiency. The performance of the present PVT system using MPCM slurry is better than that using pure tap water or water with a PCM layer. The average electrical efficiency and the maximum thermal efficiency of the system can effectively increase by 0.8% and 13.5% respectively. The slurry containing low concentration MPCM could enhance the performance, indicating the feasibility of the actual application in solar PVT system.

Model predictive control for slurry pipeline transportation of a cutter suction dredger

Cutter Suction Dredgers (CSDs) are a special type of ships designed for construction and maintenance projects of ocean and offshore engineering. During the dredging operation, CSDs can excavate nearly all kinds of soil on the sea bed, and then the dredged materials with coarse particles need to be sucked up by a slurry pump and transported to a disposal area through a long-distance pipeline. In order to avoid sedimentation of slurry in pipeline transportation, the flow rate must be maintained within a reasonable range. Otherwise, the pipeline can be blocked when the slurry density is too high. In this paper, we present a Model Predictive Control (MPC) approach to manipulate the flow rate of slurry in pipeline transportation for a CSD. To demonstrate the advantages of our proposed approach, we also implement three Proportional–Integral–Derivative (PID) controllers (i.e., conventional PID, Fuzzy-PID, and LQR-PID) to make a direct comparison. Moreover, in order to evaluate the effectiveness of our proposed approach in real scenarios, we have, in particular, built a slurry pipeline transportation platform. Both the simulation and experimental results show that our proposed MPC approach is more effective than other PID controllers in controlling the flow rate in the slurry pipeline transportation problem. The proposed approach can provide a guideline for the automated control of the slurry pump for a CSD.

Study on the optimal design of volume fracturing for shale gas based on evaluating the fracturing effect—A case study on the Zhao Tong shale gas demonstration zone in Sichuan, China

Hydraulic fracturing is the key technology in the development of shale gas reservoirs, and it mainly adopts volume fracturing technology to communicate hydraulic fractures with natural fractures to increase the drainage area. In view of the difficulty in characterizing the complex fractures created by multistaged fracturing in horizontal shale gas wells and the immaturity of fracturing optimization design methods, this study first evaluated the stimulation effect of fracturing technology based on treatment data and microseismic data. Then, the fracture characteristics after frac were considered, and a post-frac simulation was studied based on the discrete fracture network (DFN) model and the microseismic monitoring data as constraints. Finally, from the simulation results, an optimal design method of volume fracturing for shale gas was proposed based on the evaluation of the frac effects. The National Shale Gas Demonstration Zone in Zhaotong, Sichuan Basin was used as an example to study the optimal frac design of shale gas wells. The results show that (1) after optimizing the design, the optimal interval range is 50–70 m, the liquid volume of a single stage is 1800–2200 m3, the amount of sand is 80 m~120 t, and the slurry rate is 10–12 m3/min. (2) Two different frac design schemes were implemented in two wells on the same platform, and the production of the optimized design scheme was 14.7% greater than the original scheme. Therefore, the frac optimization design based on evaluating the fracturing effect can better guide the development of subsequent shale gas wells in this area.

Effect of Concentration and Suspension Agent (HPMC) on Properties of Coal Gangue and Fly Ash Cemented Filling Material

Cemented coal gangue-fly ash backfill (CGFB) mixtures are utilized as the filling materials for backfilling the underground openings in coal mines. The freshly prepared CGFB slurries are commonly transported into the gobs through a pipeline. The mixture ratio of slurry concentration and suspending agent (HPMC) plays an essential role in transporting the slurry to goaf smoothly and efficiently. In this paper, the influence of slurry concentration and HPMC on the performance of coal gangue-fly ash cemented filling material was studied based on the response surface method. The prediction model of CGFB slurry slump flow, segregation rate, and bleeding rate was constructed. It is concluded that the segregation rate and slump flow of slurry are more sensitive to the variation of concentration. On the other hand, the bleeding rate of slurry is more sensitive to the change of HPMC content. Based on the established model, the reasonable mix proportion range of slurry concentration and suspending agent (HPMC) was obtained. In addition, three new CGFB mixtures have been tested, and the experimental results are in good agreement with the predicted values.

Dynamic Mechanical Characteristics of Fractured Rock Reinforced by Different Grouts

In order to investigate the dynamic mechanical properties of the fractured rocks reinforced with different slurries, the prefractured and grouted sandy mudstone specimens were tested on a Split Hopkinson Pressure Bar (SHPB), and their dynamic failure processes were shot via a high-speed camera. The test results showed that under dynamic loading, grouting reinforcement can relieve the rock failure at the fracture part. With the increase of the impact speed, the dynamic specific strength of the modified epoxy resin grouting increases from 0.85 to 1.01, and its specific strain rate increases from 1.09 to 1.04; the dynamic specific strength and specific strain rate of cement slurry grouting increase from 1.78 to 0.95 and from 0.60 to 0.98, respectively. As a whole, the specimen reaches or approaches the dynamic parameters of the intact rock specimen after grouting repair, the stability of the rock reinforced by modified epoxy resin grouting is superior to that of the rock reinforced by cement slurry grouting, and the latter can acquire high dynamic strength under low-speed impact. The improved damage-type Zhuwangtang (ZWT) model can be used to describe the dynamic mechanical behaviors of the fractured rocks reinforced by grouting very well.

Extending Openhole Gravel-Packing Intervals through Enhanced Shunted Screens

Summary For offshore wells requiring sand control, it is beneficial to extend the openhole length to access more reserves with a reduced well count. In challenging environments (e.g., low fracture pressure, highly unconsolidated sand), gravel packing with shunt tubes has been used successfully to virtually ensure a complete pack, thereby minimizing the risk of sand-control failure. Although shunt-tube gravel-pack technologies already exist, several issues must be addressed to gravel pack longer wells. First, the extra volume of gravel passing through shunt-tube manifolds raises erosion concerns. Second, the burst rating of the entire shunt system needs to be increased to allow continuous packing through shunts in a heel-to-toe fashion. Third, higher leakoff through the packed interval might increase gravel concentration, which increases friction and the risk of bridging inside the shunts. This study discusses the development and testing of a modified shunted screen that could extend openhole gravel-packing lengths to more than 7,000 ft with zonal isolation. The first step was to use computational fluid dynamics (CFD) simulations to investigate the erosion-prone areas in our existing conventional shunted-screen-technology (SST) manifold design. The CFD results were then used to modify the manifold and make it more resistant to erosion. Prototypes were manufactured and erosion tests were conducted to validate and qualify the new design for targeted proppant concentrations, flow rates, and treatment volumes. Any weak areas found in the shunt system were modified to enable higher burst pressure. The modified shunt system was then independently tested to quantify the burst limits. The concerns regarding high leakoff, friction, and bridging inside the tubes were first addressed by means of experimentation. The first nozzle distance was then modified according to these results. Verification of the modified system design was performed by means of gravel-pack testing on a full-scale model. It was observed that the proposed enhanced-SST (ESST) had no erosion failure after 450,000 lbm of proppant at a slurry rate of 5 bbl/min. The proposed ESST was successfully tested for 10,000-psi burst pressure after the erosion test. The initial motivation, design changes, and tests that led to the development of the modified system are presented herein.