The second natural gas hydrate production test in the South China Sea

Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017.Based on the understanding of the first production test,the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment,numerical and experimental simulation,and onshore testing of the reservoirs.After that,it conducted the second offshore NGH production test in 1225 m deep Shenhu Area,South China Sea(also referred to as the second production test)from October 2019 to April 2020.During the second production test,a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met,including wellhead stability,directional drilling of a horizontal well,reservoir stimulation and sand control,and accurate depressurization.As a result,30 days of continuous gas production was achieved,with a cumulative gas production of 86.14×104 m3.Thus,the average daily gas production is 2.87×10^4 m^3,which is 5.57 times as much as that obtained in the first production test.Therefore,both the cumulative gas production and the daily gas production were highly improved compared to the first production test.As indicated by the monitoring results of the second production test,there was no anomaly in methane content in the seafloor,seawater,and atmosphere throughout the whole production test.This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs.The industrialization of hydrates consists of five stages in general,namely theoretical research and simulation experiments,exploratory production test,experimental production test,productive production test,and commercial production.The second production test serves as an important step from the exploratory production test to experimental production test.

CuS nanoenzyme against bacterial infection by in situ hydroxyl radical generation on bacteria surface

Nanoenzyme-mediated antibacterial strategies have been widely exploited to overcome the shortcomings(such as drug resistance and mild-to-severe side effects) of antibiotic therapy.The peroxidase-like activity of nanoenzymes possesses great potential against bacterial infection by the generation of hydroxyl radical(·OH) in the specific microenvironment.However,the lifetime of-OH is extremely short,and a large amount of the ·OH generated within the infection microenvironment cannot come into contact with bacteria quickly enough,thus resulting in low treatment efficiency.Here,chitosan-oligosaccharide-modified CuS nanoparticles possessing positive charges(PCuS NPs) were prepared using a one-pot method.PCuS NPs exhibited efficient peroxidase-like activity.Importantly,the PCuS NPs can combine with bacteria via electrostatic attraction.The direct contact between the PCuS NPs and bacteria enabled the generation of ·OH in situ on the bacterial surface,ultimately leading to a high antibacterial efficacy at a low concentration in the presence of H_(2)O_(2).At an effective antibacterial concentration,the PCuS NPs exhibited high cytocompatibility.Furthermore,in vivo results revealed that PCuS NPs not only decreased the size of abscesses but also reduced inflammation and promoted collagen fiber formation.Therefore,PCuS NPs possess great potential against bacterial infection via in situ ·OH generation based on electrostatic attraction.