Practices and Advances in Exploring the Subsurface Structure and Its Temporal Evolution with Repeatable Artificial Sources

The earth's structure may change with time under natural or anthropogenic loading.Monitoring the subtle changes of the subsurface structure with repeatable seismic sources such as repeating earthquakes,ambient seismic noise and artificial sources has become one of the hot topics in seismological research. These studies provide important clues in understanding the physical process of hazardous events such as earthquakes and volcanic eruptions. In this review we introduce the practices and advances in exploring and monitoring the subsurface structure with artificial seismic sources. This review is orgainzed as follows. Firstly,we describe the studies on the characteristics of different types of seismic source( especially the airgun source). Then the advances on data processing and mechanical understanding are depicted. At the end of this review,we reveal the prospects of future study of exploration and monitoring of the subsurface structure and its temporal variations using artificial sources.

Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.

Alkylation of benzene with propylene catalyzed by FeCl_(3)-chloropyridine ionic liquid

Alkylation of benzene with propylene was carried out with FeCl_(3)-chloro-butyl-pyridine(FeCl_(3)-[bpc])ionic liquid as catalyst to obtain cumene.Significant improvements in propylene conversion and cumene selectivity under mild reaction conditions were attained by modification of the catalyst with HCl.Under 20℃,0.1 MPa,reaction time 5 min,mole ratio of benzene to propylene 10:1 and mass ratio of FeCl_(3)-[bpc]to benzene 1:100,conversion of propylene can increase from 83.60%to 100.00%and selectivity of cumene can increase from 90.86%to 98.47%.If reaction is carried out in following two stages,the result will be very good.At the initial stage of the reaction,alkylation is the main reaction and a higher conversion of propylene is obtained at a lower tem-perature.At the later stage of the reaction,transalkylation is the main reaction and selectivity to cumene can be increased by appropriately raising the reaction temperature.