Flow Back Mechanism Study of Multi-Stage Fracturing of Shale Gas Horizontal Wells

At present,flowback management after fracturing of shale gas horizontal wells mainly depends on field experience.By combining gas reservoir simulation model and wellbore flow model,multistage fracturing flowback pattern of shale gas horizontal wells was simulated preliminarily.Based on the orthogonal design method,13 factors including rock matrix,fracture,and production are taken into consideration.The results indicate that the factors affecting flowback recovery rank in descending sequence as viscosity of gel breaking fluid,pressure coefficient,bottom hole flowing pressure,total stages,fluid volume injected per stage,half fracture length,flowback rate,flowback time,fracture conductivity,irreducible water saturation,fracture shape,propped fracture profile,and adsorption gas content.To optimize flowback effect,controllable factors among those mentioned above can be used to adjust fracture treatment parameters,and the uncontrollable factors can be used in well and interval candidate selection.The research results have been put into application in shale gas fracturing in Jiaoshiba Block of Fuling in Chongqing,the flowback and production effect after fracturing is very encouraging,where gas production of several horizontal wells reach more than 100,000 m3/d after fracturing,and the decline rate is very low.