Experimental of the influence of mineral composition and normal stress on the frictional slip of shale

Natural fractures are widely distributed in shale reservoirs.During the hydraulic fracturing process,frictional slip occurring on natural fractures can increase the reservoir permeability and is of great significance to improve the efficiency of reservoir stimulation.Shale contains a large amount of clay and organic matter,and its frictional behavior is different from that of other previously studied lithologies.In this paper,the frictional behavior of shale is analyzed,and the results show that the frictional behavior is controlled by the content of clay and organic matter.As the content of clay and organic matter increases,the micro support type transforms from the particle support mode by hard quartz mineral to matrix support mode by plastic clay and organic matter.Accordingly,the shear strength and friction coefficient of shale both decrease,and the shear type transforms from brittle to plastic.When the content of clay and organic matter is low,the asperity of friction surfaces will break in a brittle manner and the wear degree of surfaces is low.Therefore,fractures are still featured by moderate apertures after friction.The lower the content of clay and organic matter is,the easier the asperity of crack surfaces supports themselves,and the higher the fracture residual permeability is.Thus,promoting shear slip is the main measure of reservoir stimulation.However,when the content of clay and organic matter is high,the remaining post-slip fracture aperture is small.It is difficult to increase reservoir permeability through the frictional slip of natural fractures,and in this situation,the proppant support efficiency needs to be improved.

Effects of herbicide butachlor application on the growth of periphytic biofilms and nitrogen loss in paddy systems

The application of butachlor as an herbicide in paddy fields is widely practiced,aiming to increase rice yield by directly or indirectly influencing the paddy environment.Periphytic biofilms,which form at the soil-water interface in paddy fields,are complex bioaggregates that play an important role in nitrogen (N) cycling.The objective of this study was to investigate the effect of butachlor on periphytic biofilm growth and N cycling under both light and dark conditions in the laboratory.The results revealed that butachlor application hindered the growth of periphytic biofilms and led to the dominance of Cyanobacteria as the primary prokaryotes,while inhibiting the development of eukaryotic Trebouxiophyceae.Furthermore,the application of butachlor reduced the richness and diversity of prokaryotes,but increased those of eukaryotes in periphytic biofilms.The light treatments exhibited higher total N loss because light favored periphytic biofilm growth and enhanced ammonium (NH_(4)^(+)) assimilation and nitrification.Additionally,butachlor application resulted in the increased retention of NH_(4)^(+)-N and nitrate (NO_(3)^(-))-N and an increase in N loss via denitrification.The abundances of functional genes encoding enzymes such as ammonia monooxygenase,nitrite reductase,and nitrous oxide reductase were increased by butachlor application,favoring nitrification and denitrification processes.Overall,the results suggest that butachlor application leads to an increase in total N loss mainly through denitrification in paddy systems,particularly in the presence of periphytic biofilms.Thus,the results may provide valuable insights into the changes in periphytic biofilm growth and N cycling induced by butachlor,and future studies can further explore the potential implications of these changes in paddy soils.