Research methods and devices for hydrate characteristics during oil and gas transportation:A review

Due to the high-pressure and low-temperature exploitation environment,the characteristics of hydrates are directly related to the safety of pipeline transportation,which is an important research topic for deep-sea flow assurance.In this review,six kinds of extensively used experimental equipment and three types of hot computer simulation methods,which are employed to explore the hydrate characteristics under deep-sea conditions,are comprehensively summarized,covering micro to macro research scales.The experimental equipment includes rotational rheometer,flow loop,high-pressure reactor,differential scanning calorimeter(DSC),micromechanical force(MMF)testing apparatus and microscopic morphology observation(MMO)device.The computer simulation methods involve numerical simulation,molecular dynamics(MD)simulation,Monte Carlo(MC)simulation and first-principles calculation.Their advantages and disadvantages are compared in detail,and their basic principles,main applications and the latest research progress are introduced.Some suggestions for future research methods are also provided.This work aims to help readers quickly grasp the characteristics of the most used research methods,choose suitable methods for their study and further expand these methods,so as to advance the development in hydrate research area.

An Experimental Study on the Drag Property of High-Temperature Particles Falling into Cold Liquid Pool

This experiment is to study the special resistant induced by the high-speed evaporation surrounding themoving high-temperature particles. An observable equipment was designed, in which the first 11 experiments wereperformed by pouring one or several Zirconia spheres with various high-temperature and a diameter of 3～ 10 mminto a water pool. The particles falling-down speeds were recorded by high-speed photographic instrumentation,and pressures and water temperatures were measured. A comparison between the experiments with cold and hotspheres respectively, employing three different sphere types each, was presented. The experimental data, com-pared with the theory of the evaporation drag model, are nearly identical.

Compaction and seepage characteristics of broken coal and rock masses in coal mining:A review in laboratory tests

Broken coal and rock(BCR)are an important component medium of the caving zone in the goaf(or gob),as well as the main filling material of fault fracture zone and collapse column.The compaction seepage characteristics of BCR directly affect the safe and efficient mining of coal mines.Thus,numerous laboratory studies have focused on the compaction seepage characteristics of BCR.This paper first outlines the engineering problems involved in the BCR during coal mining including the air leakage,the spontaneous combustion,the gas drainage,and the un-derground reservoirs in the goaf.Water inrush related to tectonics such as faults and collapse columns and surface subsidence related to coal gangue filling and mining also involve the compaction seepage characteristics of BCR.Based on the field problems of BCR,many attempts have been made to mimic field environments in laboratory tests.The experimental equipment(cavity size and shape,acoustic emission,CT,etc.)and experimental design for the BCR were firstly reviewed.The main objects of laboratory analysis can be divided into compression tests and seepage test.During the compaction test,the main research focuses on the bearing deformation characteristics(stress-strain curve),pore evolution characteristics,and re-crushing characteristics of BCR.The seepage test mainly uses gas or water as the main medium to study the evolution characteristics of permeability under different compaction stress conditions.In the laboratory tests,factors such as the type of coal and rock mass,particle size,particle shape,water pressure,temperature,and stress path are usually considered.The lateral compression test of BCR can be divided into three stages,including the self-adjustment stage,the broken stage,and the elastic stage or stable stage.At each stage,stress,deformation,porosity,energy,particle size and breakage rate all have their own characteristics.Seepage test regarding the water permeability experiment of BCR is actually belong to variable mass seepage.While the experimental test still focuses on the influence of stress on the pore structure of BCR in terms of gas permeability.Finally,future laboratory tests focus on the BCR related coal mining including scaling up,long term loading and water immersion,mining stress path matching were discussed.

Development on test equipment of coal slurry mixing tank

A coal slurry mixing tank is a key piece of equipment in the preparation of coal slurry for direct coal liquefaction.It is a gas-liquid-solid three-phase mixing device.Based on the performance of the existing coal slurry mixing equipment,a type of test equipment for horizontal continuous coal slurry preparation was developed,but to this point has limited research results.The test equipment consists of a mixing cylinder,mixer,stirring impeller and other components.Slurry mixing experiments were undertaken using the prototype,testing the performance of the device.A mathematical model was proposed specifically for the operation of a coal slurry mixing tank that is horizontally operated with high slurry concentration and rotary flow.The flow field in the horizontal coal mixing tank was simulated with the computational fluid dynamic (CFD) method.The experimental results match well with the CFD simulation results.Results show that the test device of a coal slurry mixing tank can be used to model the mixing of pulverized coal and the solvent oil.A strong correlation was obtained.