A Comparative Study of High-viscosity Cement Percutaneous Vertebroplasty vs. Low-viscosity Cement Percutaneous Kyphoplasty for Treatment of Osteoporotic Vertebral Compression Fractures

The clinical effects of two different methods–high-viscosity cement percutaneous vertebroplasty（PVP） and low-viscosity cement percutaneous kyphoplasty（PKP） in the treatment of osteoporotic vertebral compression fractures（OVCFs） were investigated. From June 2010 to August 2013, 98 cases of OVCFs were included in our study. Forty-six patients underwent high-viscosity PVP and 52 patients underwent low-viscosity PKP. The occurrence of cement leakage was observed. Pain relief and functional activity were evaluated using the Visual Analog Scale（VAS） and Oswestry Disability Index（ODI）, respectively. Restoration of the vertebral body height and angle of kyphosis were assessed by comparing preoperative and postoperative measurements of the anterior heights, middle heights and the kyphotic angle of the fractured vertebra. Nine out of the 54 vertebra bodies and 11 out of the 60 vertebra bodies were observed to have cement leakage in the high-viscosity PVP and low-viscosity PKP groups, respectively. The rate of cement leakage, correction of anterior vertebral height and kyphotic angles showed no significant differences between the two groups（P〉0.05）. Low-viscosity PKP had significant advantage in terms of the restoration of middle vertebral height as compared with the high-viscosity PVP（P〈0.05）. Both groups showed significant improvements in pain relief and functional capacity status after surgery（P〈0.05）. It was concluded that high-viscosity PVP and low-viscosity PKP have similar clinical effects in terms of the rate of cement leakage, restoration of the anterior vertebral body height, changes of kyphotic angles, functional activity, and pain relief. Low-viscosity PKP is better than high-viscosity PVP in restoring the height of the middle vertebra.

Development of self-generated proppant based on modified low-density and low-viscosity epoxy resin and its evaluation

Hydraulic fracturing is a critical technology for the economic development of unconventional oil and gas reservoirs.The main factor influencing fracture propping and reservoir stimulation effect is proppant performance.The increasing depth of fractured oil and gas reservoirs is causing growing difficulty in hydraulic fracturing.Moreover,the migration of conventional proppants within the fracture is always limited due to small fracture width and rigid proppant structure.Thus,proppants with good transportation capacity and fracture propping effects are needed.First,a novel self-generated proppant based on toughened low-viscosity and low-density epoxy resin was developed to satisfy this demand.Then,proppant performances were evaluated.Low-viscosity and low-density epoxy resin was generated when the thiol-ene click chemical reaction product of eugenol and 1-thioglycerol reacts with the epichlorohydrin.Then,the resin was toughened with graphite particles to increase its compressive strength from50.8 to 72.1 MPa based on micro-cracking mechanism and crazing-nail anchor mechanism.The adduct of diethylene triamine and butyl glycidyl ether and the Si O2 nanoparticles were treated as the curing agent and emulsifier respectively to form the emulsion.The emulsion is transformed into solid particles of various sizes within a reservoir to prop the fracture.Evaluation shows good migration capacity of this self-generated proppant due to the low density of epoxy resin.

Dynamic evolution of low-viscosity fuel particle distribution driven by constant flow

The effects of mass concentration and injection pressure on the atomization characteristics of low-viscosity fuel spray are studied in a constant-volume chamber.Microscopic spray parameters are measured by laser diffraction at different axial and radial positions downstream of the nozzle.The results show that the atomization effect is inhibited linearly with the increase of mass concentration.The increase of injection pressure promotes the droplet breakup.However,the trend gradually weakens and becomes more noticeable at high concentrations.Comparing with the concentration,the influence of the injection pressure on the atomization characteristics is dominant.Although low concentration and high injection pressure can promote the droplet breakup,they also increase the probability of droplet collision,resulting in droplet aggregation.This is more evident in low-viscosity fuels.The droplet size increases in the axial direction owing to the aggregation.However,the diameter decreases in the radial direction owing to the outward deflection of small droplets caused by air turbulence and entrainment.In addition,the high-velocity airflow significantly promotes the droplet breakup near the nozzle and spray axis regions and inhibits the aggregation effect.However,the lower-viscosity fuels keep smaller droplet sizes and better atomization in the whole spraying process,which is easier to realize than the higher-viscosity fuels.Overall,low concentration,high injection pressure,and low viscosity of fuel have beneficial effects on the droplet breakup.This is very important for improving the atomization effect of fuel.

Low-viscosity oligoether esters(OEEs)as high-efficiency lubricating oils:Insight on their structure‒lubricity relationship

Development of energy-efficient lubricants is a way to reduce energy consumption for transportation,with the tendency to design molecules that are beneficial in reducing the viscosity of synthetic oils.Oligoether esters(OEEs),as a low-viscosity ester base oil,have characteristics such as simple synthesis and excellent lubrication effect;however,the application of OEEs in tribology field has rarely been investigated.The objective of the present study is to investigate the effect of structure on the lubricating performance of OEEs and to develop a predictive model for OEEs based on quantitative structure‒property relationship(QSPR)through a combination of experiment and statistical modeling.Results showed that glycol chains contribute positively to lubrication with the ether functional groups increasing the sites of adsorption.Compared to branched-chain OEEs,straight-chain OEEs exhibited reduced wear,which was mainly due to the thicker adsorption film formed by the straight-chain structure.Furthermore,carbon films were detected on lightly worn surfaces,indicating that OEEs underwent oxidation during the friction process.Based on the results of principal component analysis(PCA)and partial least squares(PLS),it could be found that the predictive models of viscosity‒temperature performance,thermal stability performance,coefficient of friction(COF),and wear volume(WV)performed well and robustly.Among them,COF and WV can be best predicted with an R^(2) of about 0.90.

A novel dandelion-based bionic proppant and its transportation mechanism in different types of fractures

Low-permeability reservoirs are generally characterized by low porosity and low permeability.Obtaining high production using the traditional method is technologically challenging because it yields a low reservoir recovery factor.In recent years,hydraulic fracturing technology is widely applied for efficiently exploiting and developing low-permeability reservoirs using a low-viscosity fluid as a fracturing fluid.However,the transportation of the proppant is inefficient in the low-viscosity fluid,and the proppant has a low piling-up height in fracture channels.These key challenges restrict the fluid(natural gas or oil)flow in fracture channels and their functional flow areas,reducing the profits of hydrocarbon exploitation.This study aimed to explore and develop a novel dandelion-bionic proppant by modifying the surface of the proppant and the fiber.Its structure was similar to that of dandelion seeds,and it had high transport and stacking efficiency in low-viscosity liquids compared with the traditional proppant.Moreover,the transportation efficiency of this newly developed proppant was investigated experimentally using six different types of fracture models(tortuous fracture model,rough fracture model,narrow fracture model,complex fracture model,large-scale single fracture model,and small-scale single fracture model).Experimental results indicated that,compared with the traditional proppant,the transportation efficiency and the packing area of the dandelion-based bionic proppant significantly improved in tap water or low-viscosity fluid.Compared with the traditional proppant,the dandelionbased bionic proppant had 0.1-4 times longer transportation length,0.3-5 times higher piling-up height,and 2-10 times larger placement area.The newly developed proppant also had some other extraordinary features.The tortuosity of the fracture did not influence the transportation of the novel proppant.This proppant could easily enter the branch fracture and narrow fracture with a high packing area in rough surface fractures.Based on the aforementioned characteristics,this novel proppant technique could improve the proppant transportation efficiency in the low-viscosity fracturing fluid and increase the ability of the proppant to enter the secondary fracture.This study might provide a new solution for effectively exploiting low-permeability hydrocarbon reservoirs.