Numerical simulation of foam diversion acidizing in heterogeneous reservoirs

Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers.Based on the foam diversion principle,the gas trap theory,and volume conservation principle,the foam slug diversion acidizing model was established and solved considering the change of bottomhole temperature and deviation factor of foam.The simulation results show that the change of temperature has a great influence on the diversion effect at the initial stage of injection,but a small influence at the middle and late stage.The effect of temperature on the highly permeable layer is greater than that of temperature on the low permeability layer.The deviation factor of foam is mainly controlled by temperature at the initial stage,and by pressure at the middle and late stage,and the whole process shows a downward trend,which has little influence on the diversion effect.The quasi-skin factor of gas trap is the most important parameter that influences the effect of foam diversion.The water saturation of the low permeability layer rises faster than that of the high permeability layer,and the effect of diversion is obvious.The research results have a strong guiding significance for foam diversion acidizing.

Soil Microbial Community Composition During Natural Recovery in the Loess Plateau, China

This study aimed to determine the characteristics of soil microbial community composition and its relationship with soil chemical properties during natural recovery in the Loess Plateau.The soil microbial community composition was analyzed by comparing the soil microbial phospholipid fatty acids（PLFAs） of eight croplands abandoned for 1,3,5,10,13,15,20,and 30 yr in the Dunshan watershed,northern Loess Plateau,China.The results showed that soil organic carbon,total nitrogen,soil microbial biomass carbon,and soil microbial biomass nitrogen significantly increased with the abandonment duration,whereas the metabolic quotient significantly decreased.The Shannon richness and Shannon evenness of PLFAs significantly increased after 10 yr of abandonment.Gram-negative,Gram-positive,bacterial,fungal,and total PLFAs linearly increased with increased abandonment duration.Redundancy analysis showed that the abandonment duration was the most important environmental factor in determining the PLFA microbial community composition.The soil microbial PLFAs changed from anteiso-to iso-,unsaturated to saturated,and short-to long-chain during natural recovery.Therefore,in the Loess Plateau,cropland abandonment for natural recovery resulted in the increase of the soil microbial PLFA biomass and microbial PLFA species and changed the microbial from chemolithotrophic to a more heterotrophic community.