Experimental Investigation on Vertical Hydraulic Transport of Ores in Deepsea Mining

Deepsea mining has been proposed since the 1960s to alleviate the lack of resources on land.Vertical hydraulic transport of collected ores from the seabed to the sea surface is considered the most promising method for industrial applications.In the present study,an indoor model test of the vertical hydraulic transport of particles was conducted.A noncontact optical method has been proposed to measure the local characteristics of the particles inside a vertical pipe,including the local concentration and particle velocity.The hydraulic gradient of ore transport was evaluated with various particle size distributions,particle densities,feeding concentrations and mixture flow velocities.During transport,the local concentration is larger than the feeding concentration,whereas the particle velocity is less than the mixture velocity.The qualitative effects of the local concentration and local fluid velocity on the particle velocity and slip velocity were investigated.The local fluid velocity contributes significantly to particle velocity and slip velocity,whereas the effect of the local concentration is marginal.A higher feeding concentration and mixture flow velocity result in an increased hydraulic gradient.The effect of the particle size gradation is slight,whereas the particle density plays a crucial role in the transport.

Numerical Investigation on Inclined Hydraulic Transport of Large Particles for Deepsea Mining

Hydraulic transport in pipelines is the most promising conveying method for large ore particles in deepsea mining.The dynamic performances of particles during transportation in vertical,inclined and horizontal pipelines are significant for the design of hydraulic transport systems.In the present study,we focus on the statistical characteristics and flow regimes of the mixture composed of ore particles and seawater in the pipelines.Numerical simulations are conducted by using Computational Fluid Dynamics(CFD)and Discrete Element Method(DEM).The influences of inclination angle and particle diameter are evaluated through two sets of numerical tests.The regulation of the inclined transport is totally different from that of the vertical transport,whereas the dynamics of the mixtures in inclined and horizontal pipes are similar.A number of particles accumulate on the pipe wall even with a small inclination angle.Large hydraulic gradient and local concentration would occur when the inclination angle of the pipe is in the range of30°-60°.With the decrease of particle diameter,the particle flow becomes uniform,reflected by the almost uniform particle distribution in the vertical pipe and the clear interface between the suspended load and the bed-load in the inclined pipe.However,small particles will introduce larger local concentrations and hydraulic gradients in the inclined pipe,which is not conducive to particle transport.

Deployment of Self-Propelled Modular Transporter for Vessel Installation

The traditional way of installing large vessels has always been to employ the use of cranes. The Water Handling Debottlenecking Project team has, instead, made use of a different technology—employing a Self-Propelled Modular Transporter (SPMT) to install nine vessels in situ. These SPMT units have many advantages over crane installations, such as safety and efficiency, not to mention lower costs due to their self-propelled capabilities.

Experimental study on the effects of big particles physical characteristics on the hydraulic transport inside a horizontal pipe

This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe.The particles are spherical and are large with respect to the diameter of the pipe(8%,10%,16% and 25%).Experiments were done to test the important parameters in solid transport(pressure,velocity,etc.).As a result,the relationship between the pressure gradient forces and the mixture velocity was substantially different from the pure liquid flow.However,in a single-phase flow a monotonous behavior of the pressure drop curve is observed,and the curve of the solid particle flow attains its minimum at the critical velocity.The regimes are characterized with differential pressure measurements and visualizations.

Numerical Modelling of Proppant Transport in Hydraulic Fractures

The distribution of proppant injected in hydraulic fractures significantly affects the fracture conductivity and well performance.The proppant transport in thin fracturing fluid used during hydraulic fracturing in the unconventional reservoirs is considerably different from fracturing fluids in the conventional reservoir due to the very low viscosity and quick deposition of the proppants.This paper presents the development of a three-dimensional Computational Fluid Dynamics(CFD)modelling technique for the prediction of proppant-fluid multiphase flow in hydraulic fractures.The proposed model also simulates the fluid leak-off behaviour from the fracture wall.The Euler-Granular and CFD-Discrete Element Method(CFD-DEM)multiphase modelling approach has been applied,and the equations defining the fluid-proppant and inter-proppant interaction have been solved using the finite volume technique.The proppant transport in hydraulic fractures has been studied comprehensively,and the computational modelling results of proppant distribution and other flow properties are in good agreement with the published experimental study.The parametric study is performed to investigate the effect of variation in proppant size,fluid viscosity and fracture width on the proppant transport.Smaller proppants can be injected early,followed by larger proppants to maintain high propping efficiency.This study has enhanced the understanding of the complex flow phenomenon between proppant and fracturing fluid and can play a vital role in hydraulic fracturing design.

Numerical Simulation of Hydraulic Transport of Sand-Water Mixtures in Pipelines

The development of empirical model for the hydraulic transport of sand-water mixtures is important for the design of economical solid-liquid transportation system in chemical and waste-disposal industries. The hydraulic transport characteristics of sand-water mixtures in circular pipelines are numerically investigated by using the FLUENT commercial software. Eulerian granular multiphase (EGM) model with the k-e turbulent model is used for the computation. Present method is validated by the computed values with the measured data. The effect of the concentration and pipe sizes on the relative solid effect is numerically investigated. It is found that the effect of the volumetric delivered concentration on both hydraulic gradient and solid effect increases as the Reynolds number decreases. When the Reynolds number is small, the increase in the volumetric delivered concentration has an effect of decreasing the hydraulic gradient whereas the solid effect increases with the volumetric delivered concentration stepping up. The effect of the pipe diameter is not the critical parameter for deciding the values of the relative solid effect in the sand-water mixture transportation.

Dynamic fluid transport property of hydraulic fractures and its evaluation using acoustic logging

The existing acoustic logging methods for evaluating the hydraulic fracturing effectiveness usually use the fracture density to evaluate the fracture volume, and the results often cannot accurately reflect the actual productivity. This paper studies the dynamic fluid flow through hydraulic fractures and its effect on borehole acoustic waves. Firstly, based on the fractal characteristics of fractures observed in hydraulic fracturing experiments, a permeability model of complex fracture network is established. Combining the dynamic fluid flow response of the model with the Biot-Rosenbaum theory that describes the acoustic wave propagation in permeable formations, the influence of hydraulic fractures on the velocity dispersion of borehole Stoneley-wave is then calculated and analyzed, whereby a novel hydraulic fracture fluid transport property evaluation method is proposed. The results show that the Stoneley-wave velocity dispersion characteristics caused by complex fractures can be equivalent to those of the plane fracture model, provided that the average permeability of the complex fracture model is equal to the permeability of the plane fracture. In addition, for fractures under high-permeability(fracture width 10~100 μm, permeability ~100 μm^(2)) and reduced permeability(1~10 μm, ~10 μm^(2), as in fracture closure) conditions, the Stoneley-wave velocity dispersion characteristics are significantly different. The field application shows that this fluid transport property evaluation method is practical to assess the permeability and the connectivity of hydraulic fractures.

Water-salt transport characteristics of saline soil under hydraulic remediation measures in the Yellow River Delta region of China

To understand the water-salt transport process of saline soils in the Yellow River Delta region under traditional hydraulic remediation measures and to determine its engineering parameters, in this study, laboratory investigations were made to measure the soil salt content using three remediation practices under simulated rainfall conditions. The results indicated that under the rainfall intensity of 100 mm/h, 6-8 h are needed when the soil salt content tends to be constant. The distribution of the salt content presents a typically symmetrical shape regardless of the position of the saline soil relative to the concealed pipe, the open ditch, and the vertical shaft. The two-parameter exponential function indicates the relationship between the soil desalination rate and the horizontal distance from the pipe, the ditch or the shaft. The maximum spacing to build the salt drainage engineering of the concealed pipe, the open ditch or the vertical shaft in the laboratory is 4.79 m, 2.88 m, and 2.19 m, respectively. The effectiveness of salt drainage for coastal saline soils can be ranked from largest to smallest as the concealed pipe, the open ditch and the vertical shaft. The findings provide an experimental basis and reference for the application of hydraulic measures to remediate saline soils in this region.

Coupled hydro-thermo-mechanical modeling of hydraulic fracturing in quasi-brittle rocks using BPM-DEM

This paper presents an improved understanding of coupled hydro-thermo-mechanical(HTM) hydraulic fracturing of quasi-brittle rock using the bonded particle model(BPM) within the discrete element method(DEM). BPM has been recently extended by the authors to account for coupled convective econductive heat flow and transport, and to enable full hydro-thermal fluidesolid coupled modeling.The application of the work is on enhanced geothermal systems(EGSs), and hydraulic fracturing of hot dry rock(HDR) is studied in terms of the impact of temperature difference between rock and a flowing fracturing fluid. Micro-mechanical investigation of temperature and fracturing fluid effects on hydraulic fracturing damage in rocks is presented. It was found that fracture is shorter with pronounced secondary microcracking along the main fracture for the case when the convectiveeconductive thermal heat exchange is considered. First, the convection heat exchange during low-viscosity fluid infiltration in permeable rock around the wellbore causes significant rock cooling, where a finger-like fluid infiltration was observed. Second, fluid infiltration inhibits pressure rise during pumping and delays fracture initiation and propagation. Additionally, thermal damage occurs in the whole area around the wellbore due to rock cooling and cold fluid infiltration. The size of a damaged area around the wellbore increases with decreasing fluid dynamic viscosity. Fluid and rock compressibility ratio was found to have significant effect on the fracture propagation velocity.

Chloride ion penetration into concrete under hydraulic pressure

The lining concrete of subsea tunnel services under combined hydraulic pressure, mechanical and environmental loads. The chloride ion and water penetrations into concrete under hydraulic pressure were investigated. The experimental results indicate that the water penetration depth, chloride ion transportation depth, and the concentration of chloride ion ingression into concrete increase with raised hydraulic pressure and hold press period. But the chloride ion transportation velocity is only 53% of that of water when concrete specimens are under hydraulic pressure. The chloride transportation coefficient of concrete decreases with hold press period as power function. And that would increase 500% 600% in chloride transportation coefficient when the hydraulic pressure increases from 0 to 1.2 MPa. The hydraulic pressure also decreases the bound chloride ion of concrete to about zero. Besides, the low water-cementitions materials and suitable content of mineral admixture(including fly ash and slag) improve the resistance capacity of chloride penetration, and binding capacity of concrete under hydraulic pressure.

Research on Hydraulic Block Scenarios in the Land Conservation Zone of the Headwaters Area of Jinshu Bay

[Objective] The aim was to study the hydraulic block scenarios in the water source land conservation zone in Jinshu Bay so as to ensure the water quality in the water sources in Jinshu Bay.[Method] By dint of one dimension water amount and water quality mode in the river net in Taihu,the water flow movement characteristics and pollutants transportation rules in the water sources areas in Jinshu Bay under five kinds of hydraulic block scenarios were compared and discussed.[Result] After demolishing the temporary soil dam in the water source conservation zone in Jinshu Bay,water amount and pollutants increased and water quality deteriorated.It was necessary to take certain hydraulic power to block and control the pollutants in the preservation area;after demolishing the dam,there was less water amount and pollutants.The water quality improved significantly.The hydraulic block facility in the preservation area and its surroundings were all releasing and not introducing;the one along the mouth of the river of Mentianji Gang,Jinshugang and Longtanggang were introducing and not releasing,which only restricted poor-quality water in Beijing-Hangzhou Canal and Huguang Canal flowing into the conservation zone.The water into the conservation zone was all from Gonghu.The water mobility within the conservation zone was good.The regional water quality improved to the largest scale.[Conclusion] Judging from the water flow movement characteristics and pollutants transportation rules in Jinshu Bay,the fifth proposal was more appropriate.

Advances and challenges in hydraulic fracturing of tight reservoirs: A critical review

The hydraulic fracturing technology has been widely utilized to extract tight resources.Hydraulic frac-turing involves rock failures,complex fracture generation,proppant transport and fracture closure.All these behaviors affect the productivity of fractured wells.In this work,the advances and challenges in hydraulic fracturing development of tight reservoirs are summarized from following aspects:the hy-draulic fracture propagation,the proppant transport and distribution in hydraulic fractures,the calcu-lation of hydraulic fracture conductivity,and productivity and/or pressure analysis model of multi-stages fractured horizontal wells.Current fracture propagation simulation methods generate only limited propagation paths and cannot truly reflect the complexity of the propagation.The current proppant migration and distribution research is mainly focused on indoor experimental studies of proppant migration in a single fracture or branched fracture,and simulation studies on proppant migration and distribution in a small-scale single slab fracture.Whereas fractures formed after hydraulic fracturing in tight reservoirs are generally complicated.There is a lack of models for calculating complex fracture conductivity that take into consideration the effect of proppant placement and proppant distribution in fractures,fracture surface roughness and dissolution,diffusion,deposition,elastic embedding,and creep caused by stress.The productivity models of fractured horizontal wells are mostly conducted based on the original reservoir fluid saturation and pressure distribution.Most of the studies are focused only on one aspect of the fracturing process.Predications of well performance after fracturing based on these studies are often inconsistent with actual field data.The paper also discusses the future research di-rections of fracturing in tight reservoirs and the results may be used to promote the development of tight reservoirs.

土木、水利与交通工程专业“五强一化”课程体系探索与实践

基于新工科背景下的高素质复合型和管理型人才培养已经成为土建类专业的目标需求,培养体系中课程的迭代更新则是其中的关键。以浙江大学建筑工程学院土木、水利与交通工程新工科专业为例,结合新时代发展和新工科建设的实际需求,创新性地提出“土水交融通”的先进教育理念,构建了土木、水利与交通工程专业以强智能和强实践为核心的“五强一化”课程新体系,探讨了土木、水利与交通工程专业在创新与实践、前沿与智能化两个方面的改革和实践经验。“五强一化”课程新体系实现了大土木融通的培养模式,开辟了土建类本科人才培养改革的新方向,可为高校开展新工科专业建设和人才培养提供参考。

基于CFD-DEM算法的复杂裂缝支撑剂运移模拟分析

为了研究裂缝内支撑剂的运移特性,应用计算流体力学-离散元(CFD-DEM)耦合模拟技术来模拟复杂裂缝中的支撑剂运移情况。通过控制单一变量法,研究了流速、支撑剂体积分数及压裂液黏度3个参数对于支撑剂运移的影响。结果表明:适当提高支撑剂体积分数有助于提高其携液能力进而提高压裂效果;较高的注入速度会使支撑剂在入口较远处沉降,因此适当提高注入速度会促进裂缝的扩展和延伸;较高的黏度会使支撑剂在出口流出,选取适当的黏度有利于提高油气的渗透性和采收率。

金属矿山深部硬岩矿床非爆连续采矿技术及应用

随着我国矿产资源需求的不断攀升及浅层矿产资源的日益枯竭,向深部拓展开采新的矿产资源已成为必然的趋势。首先,针对传统的凿岩爆破工艺在深部开采中面临的诸多挑战,阐述了深部硬岩矿床非爆连续采矿技术及装备。然后,以某深部硬岩矿山为例,详细介绍了非爆连续采矿技术的应用实践,并展示了所带来的积极成效,为深部硬岩矿床非爆连续开采提供案例借鉴;最后,基于实践经验,结合人工智能等前沿技术,提出了矿石制浆与水力输送技术,有望为深井矿石的提升提供一种更为高效、环保的解决方案,进一步优化和提升深部矿山的开采效率和安全性。

旋转水力提升多金属结核运动特性数值模拟

采用CFD-DEM耦合方法对多金属结核提升进行模拟,研究了垂直管道中不同旋转流场旋流比对水力提升多金属结核输运特性的影响。结果表明,随着旋转流场旋流比增大,旋转强度显著增强,流体流速最大值增大,颗粒群轴向平均速度增大。旋转流场的旋转强度明显影响管道内颗粒的速度分布:速度大的颗粒逐步分布在管壁周围,速度较小的颗粒分布在管道中心处。旋转流场可降低颗粒群局部浓度,有利于降低因颗粒滞留效应引起局部浓度升高造成的输送管堵塞风险。

水平井射孔簇内支撑剂分布数值模拟

为研究水平井射孔簇内支撑剂的运移规律,建立了水平井筒几何模型,并采用欧拉双流体模型分析了不同注入流量、压裂液黏度和注入φ(砂粒)对支撑剂运移规律的影响。结果表明,在水平井筒中,支撑剂的分布向趾部偏移。增加注入流速能促进颗粒的分散,但会降低射孔内的均匀性;提高压裂液黏度能减缓颗粒沉降,有助于支撑剂的均匀分布;增加注入φ(砂粒)会增加井筒堵塞风险,因此选择注入φ(砂粒)<10%。此外,雷诺数与归一化标准差呈自然对数关系,较高的雷诺数有助于提高颗粒在射孔流出的均匀性。

梯级泵站事故停机输水明渠水力过渡过程研究

为解决梯级泵站系统因超负荷、大流量、高水位运行出现垮渠、跳闸停机等事故,而导致水力过渡过程中出现进水前池被抽干或漫顶等问题,以甘肃省景泰川电力提灌二期工程长距离输水明渠为研究对象,在多梯级泵站事故停机产生溢流的工况下,基于Realizable k-ε和VOF模型进行数值模拟计算,分析景电二期工程1#~7#干渠在调蓄系统作用下,不同渠长、坡降的水面线以及水力振荡分布规律。结果表明:泵站停机后水位出现升降交替的水力振荡现象,影响各泵站波峰水位高度不一致的主要原因是渠道坡降;不同参数特征的渠道壅水波运动的回溯距离不同,溢流堰上发生溢流的时间主要在第一次水位振荡过程中。

浅层稠油开采用全液压斜直井修井机研制

目前国内用于油田浅层稠油开采中的斜直井修井机技术相对落后,还不能满足现场作业的要求。提出了全液压斜直井修井机的设计方案和技术参数;对该修井机的主要零部件和系统(如液压系统、游动吊卡、抓管机、可调底座、支架、接送管装置、油管对中及上卸扣装置等)进行了详细设计。全液压斜直井修井机经过试制和一年多的现场应用,结果表明:其结构设计合理,使用安全可靠,减少了作业人员,大幅降低了作业人员劳动强度。

中国热带珊瑚岛优势木本植物抗风桐和草海桐的水分适应策略解析

植物水力性状能够反映植物对不同水分条件的适应能力,研究热带珊瑚岛特殊生境下优势植物的水力功能特征对深入理解热带珊瑚岛植物的水分适应策略,从而选择热带珊瑚岛植被构建和恢复的适生物种具有重要意义。该研究以中国热带珊瑚岛生境中2种优势适生木本植物:抗风桐(Pisonia grandis)和草海桐(Scaevola sericea)为研究对象,比较了其叶片和枝条的水力性状,并分析了其水分适应策略。结果表明,抗风桐的叶片栓塞抗性、枝条边材比导水率和叶片膨压丧失点显著高于草海桐,而枝条栓塞抗性、叶片导水率、边材密度和叶面积边材面积比均显著低于草海桐。抗风桐的叶片具有比枝条更强的抗栓塞能力,对水分胁迫敏感,但同时选择以高效的枝干水分运输来满足叶片高蒸腾需求的充足供水。草海桐枝条与叶片则存在水力脆弱性分区,在面临水分胁迫时叶片充当“安全阀”以保证枝干木质部的水力安全。抗风桐与草海桐能够通过协调叶片与枝条水力性状采取不同的水分适应策略,从而更好地适应热带珊瑚岛的特殊生境。