Experimental investigation and correlations for proppant distribution in narrow fractures of deep shale gas reservoirs

Hydraulic fracturing is a crucial stimulation for the development of deep shale gas reservoirs.A key challenge to the effectiveness of hydraulic fracturing is to place small proppants in complex narrow fractures reasonably.The experiments with varied particle and fluid parameters are carried out in a narrow planar channel to understand particle transport and distribution.The four dimensionless parameters,including the Reynold number,Shields number,density ratio,and particle volume fraction,are introduced to describe the particle transport in narrow fractures.The results indicate that the narrow channel probably induces fluid fingers and small particle aggregation in a highly viscous fluid,leading to particle settlement near the entrance.The low viscous fluid is beneficial to disperse particles further into the fracture,especially in the high-speed fluid velocity.The linear and natural logarithmic laws have relationships with dimensionless parameters accurately.The multiple linear regression method developed two correlation models with four dimensionless parameters to predict the bed equilibrium height and covered area of small particles in narrow fractures.The study provides fundamental insight into understanding small size proppant distribution in deep reservoirs.

Maternal peripartum bacteremia caused by intrauterine infection with Comamonas kerstersii:A case report

BACKGROUND Comamonas kerstersii(C.kerstersii)infections have considered as non-pathogenic to humans,however due to new techniques such as matrix-assisted laser desorption ionization-time of flight mass spectrometry(MALDI-TOF-MS),more cases have been identified.CASE SUMMARY This is the first report of a maternal patient with a C.kerstersii bacteremia following caesarean section.Due to the severity of the patient’s condition;high fever and rapidly progressing organ damage,the patient was transferred to the intensive care unit.C.kerstersii was detected by metagenomic next-generation sequencing testing.Based on the drug sensitivity test,appropriate antibiotic treatment was given and the patient recovered fully.CONCLUSION This case report confirms that the detection via MALDI-TOF-MS and metagenomic next-generation sequencing testing provides a reliable basis for the diagnosis of this rare bacterial infection.

Experiment and simulation of slurry flow in irregular channels to understand proppant transport in complex fractures

Slurry flow and proppant placement in irregular fractures are crucial to evaluate hydraulic fracturing stimulation but need to be better understood.This study aims to investigate how irregular fracture affects proppant transport and distribution using laboratory experiments and micro-scale numerical models.The unresolved method of the computational fluid dynamics(CFD)and the discrete element method(DEM)considers Saffman lift force,Magnus force,and virtual mass force to accurately capture the frequent interaction between proppant and slickwater.Experimental results validated the reliability of the optimized CFD-DEM model and calibrated primary parameters.The effects of crack height and width,bending angle,and distance between the crack and inlet on particle distribution were studied.The results indicated that the improved numerical method could rationally simulate proppant transport in fractures at a scale factor.The small crack height causes downward and upward flows,which wash proppant to the fracture rear and form isolated proppant dunes.A wider region in the fracture is beneficial to build up a large dune,and the high dune can hinder particle transport into the fracture rear.When the crack is close to the inlet,the primary fracture without proppants will close to hinder gas production.The smaller the bending angle,the smaller the proppant dune.A regression model can precisely predict the dune coverage ratio.The results fundamentally understand how complex fractures and natural cracks affect slurry flow and proppant distribution.

Antibiotic resistance mechanisms of Myroides sp.

Bacteria of the genus Myroides （Myroides spp.） are rare opportunistic pathogens. Myroides sp. infections have been reported mainly in China. Myroides sp. is highly resistant to most available antibiotics, but the resistance mechanisms are not fully elucidated. Current strain identification methods based on biochemical traits are unable to identify strains accurately at the species level. While 16S ribosomal RNA （rRNA） gene sequencing can accurately achieve this, it fails to give information on the status and mechanisms of antibiotic resistance, because the 16S rRNA sequence contains no information on resistance genes, resistance islands or enzymes. We hypothesized that ob- taining the whole genome sequence of Myroides sp., using next generation sequencing methods, would help to clarify the mechanisms of pathogenesis and antibiotic resistance, and guide antibiotic selection to treat Myroides sp. infec- tions. As Myroides sp. can survive in hospitals and the environment, there is a risk of nosocomial infections and pandemics. For better management of Myroides sp. infections, it is imperative to apply next generation sequencing technologies to clarify the antibiotic resistance mechanisms in these bacteria.