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Most natural gas hydrate (NGH) reservoirs have poor permeability characteristics, which is unfavorable to fluid flow and gas production. To enhance gas production, a new method of radial water jet slotting and grouting (RWJSG) was proposed to reconstruct the formation around horizontal wellbores of a horizontal well. To evaluate the effectiveness of the proposed method, a three-dimensional (3D) gas production model was constructed with reference to the NGH reservoir at the SH2 site in the South China Sea (SCS). The results show that RWJSG can effectively enhance the gas recovery of the horizontal well. Compared with an unreconstructed case, the hydrate dissociation efficiency, cumulative gas production, and average ratio of gas to water production in the RWJSG case are increased by 121.0, 116.3 and 46.1%, respectively, during the 720day production period. RWJSG can enlarge reservoir exposed area, promote pressure drop transfer, and improve gas/water flow near the wellbore. In addition, the effect of increasing production mainly depends on the slot radius and number. Within a certain range, the decrease in slot spacing and increase in slot filler permeability have positive effects. For the reservoir at SH2 site, the scheme with a radius of 5 m, a spacing of 5 m, a number of 5 and a permeability of 500 mD could achieve remarkable stimulation effect. This work provides ideas and guidance for stimulation of horizontal wells in NGH reservoirs by RWJSG.

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Particulate pollution caused by urban traffic emissions has become a significant public hazard. Many urban roads of under-viaduct spaces (UVSs) have become concentrated areas of particulate pollution. This study aims to explore the effects of landscape parameters on particulate matter in UVSs in Wuhan, China. We selected 14 types of UVS sections and nine potential environmental parameters to monitor four types of particulate matter (PM1.0, PM2.5, PM10, and TSP). Finally, linear regression analysis was employed to quantify the relative contributions of environmental parameters to the reduction in the concentration of the four types of particulate matter in the summer and winter. The results showed that particulate matter concentrations exhibit spatial and seasonal differences in UVSs. A single landscape parameter was correlated with particulate matter concentration, while compound environmental parameters had significant effects on the particulate matter concentration in UVSs. Meteorological factors and greening structures had a dominant impact on the particulate matter concentrations in summer and winter, respectively. Therefore, adjusting and optimizing the environmental parameters could reduce particulate pollution in UVSs and could have practical significance for the planning and design of UVSs.