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.

Selective modification of two-dimensional MoS_2 nanosheets by polymer grafting

As an emerging two-dimensional (2D) nanomaterial, single layer ora few layers of molybdenum disulfide (MoS_2) has drawn significant attention in the past decade. In the present work, we report a strategy in direct creating polymer brushes on MoS_2 surfaces via S—C bond in the presence of UV light. The modification of MoS_2 nanosheets can be achieved bilaterally or homolaterally by performing the UVgrafting polymerization on exfoliated MoS_2 nanosheets or a single layer of MoS_2 deposited on a silicon substrate. A series of vinyl monomers including methyl methacrylate (MMA), styrene (St) and 2-isopropenyl-2-oxazoline (IPOx) could be applied to this approach, leading to the formation of poly (methyl methacrylate) (PMMA), polystyrene (PS) and poly (2-isopropenyl-2-oxazoline) (PIPOx) brushes.AFM, IR, and XPS characterizations indicate the successful formation of homogeneous brush layers on MoS_2 surfaces. The polymer brushes modified MoS_2 may found potential applications in photo dynamic therapy and sensing technologies.

Polymeric nanoparticles of poly(2-oxazoline),tannic acid and doxorubicin for controlled release and cancer treatment

A straightforward coassembly strategy was developed for the preparation of polymeric nanoparticles driving by the intermolecular hydrogen bond between neutral poly(2-methyl-2-oxaozline)(PMeOx),tannic acid(TA) and doxorubicin hydrochloride(Dox).The occurrence of the hydrogen-bonding amongst the different functionalities within the formed nanoparticles was verified by infrared(IR) spectroscopy.Scanning electron microscopy(SEM),dynamic light scattering(DLS),UV-vis absorption and photoluminescent measurements indicated the rapid formation of uniform and water dispersible/stable nanoparticles.The relative poor stability of PMeOx-TA-Dox in fetal bovine serum(FBS) solution enabled the rapid separation of Dox and PMeOx-TA,facilitating the release of Dox and its entrance into cellular nuclei as revealed by confocal laser scanning microscopy(CLSM).The presented strategy may provide an efficient alternative for the construction of multifunctional nanomedicines.

Controlled synthesis of silver nanoparticles from polyoxometalates-immobilized poly(4-vinylpyridine) brushes

This contribution reports the immobilization of polyoxometalate(POM)into poly(4-vinyl pyridine)(P4 VP)brushes and the controlled reduction of silver ions,in-situ generating metal nanoparticles in the brushes.P4 VP brushes were straightforwardly created by UV-assisted photopolymerization of 4-vinyl pyridine(4VP)on silicon or glass substrates.Phosphotungstic acid(H3 PW12 O40),one of the most widely used Keggin-type POM was anchored onto these pyridine moieties through electrostatic interaction,leading to the P4 VP/POM hybrid brushes.The immobilized POM was further reduced to heteropolyblue,which could be used to generate silver nanoparticles in a controlled fashion.AFM,UV-vis and IR characterization indicate that P4 VP brushes not only provide an efficient platform in the controlled preparation of Ag nanoparticles,but also efficiently disperse and stabilize POM,thus preventing the aggregation of the generated Ag nanoparticles.

Polymer brushes on hydrogen-terminated silicon substrates via stable Si--C bond

We demonstrate a straightforward and efficient method for the creation of polymer brushes on hydrogen-terminated silicon substrates through the UV-induced photopoiymerization. The surface grafting polymerization is applicable to a series of monomers, allowing the direct formation of homogeneous polymer coatings ranging from hydrophilic poly（2-isopropenyl-2-oxazoline） （PIPOx）, amphiphilic poly（N-isopropyl acrylamide） （PNIPAM）, to hydrophobic polystyrene （PS） and poly（4- （1H,1H,2H,2H-perfiuorohexyl）oxymethylstyrene） （PPHMS） on Si（100） and Si（lll） surfaces via stable Si--C bonds. Polymerization kinetic investigation indicates a linear increase of polymer layer thickness with the polymerization time. Moreover, the as-prepared polymer brushes exhibit superior stability against basic conditions in contrast to those that were formed on silicon substrates via conventional Si--O--C bond.