Optimization Of Well Closure Time After Fracturing In Tight Reservoir Based On Imbibition Experiment

Tight oil has become an important substitute resource for oil fields in China.The most common stimulation measure for tight reservoir development is reservoir fracturing.In the process of production and development after fracturing,it is found that there is a certain relationship between crude oil production and well plugging time after fracturing.It is considered that the main reason is the imbibition of fluid in the fracture and crude oil in the pore.Therefore,it is necessary to study the influence of fracturing fluid properties on reservoir imbibition effect in the process of hydraulic fracturing,optimize the well killing time,give full play to the imbibition effect between fracture and matrix,and improve the development effect of tight reservoir.Based on the investigation and research,on the basis of a large number of literature at home and abroad,analyzes the basic principle and influence factors of absorption,and the experimental study on the dense oil reservoir characteristics,different concentration of surfactant fracturing fluid is studied to reduce the interfacial tension and improve the wettability of the substrate,at the same time,through the dynamic and static seepage experiment study of dense oil reservoir seepage law of suction in fracturing fluid system,The optimum time of borehole tightness is obtained by numerical software simulation.The results show that compared with conventional reservoirs,tight oil reservoirs have the characteristics of low porosity,low permeability and prominent reservoir sensitivity.Through static imbibition experiment,the imbibition effect is best in the filtrate of fracturing fluid with surfactant concentration of 0.9%.Reservoir permeability and imbibition temperature have great influence on imbibition effect.The dynamic imbibition experiment shows that the imbibition recovery rate has a certain relationship with the flow velocity in the fracture,and there is an optimal flow rate to improve the imbibition recovery rate,at which the interaction of capillary force and viscous force is the best,and the imbibition efficiency is the best at the optimal flow rate.When the tight oil reservoir is fractured and imbibed,the combination of fracturing and stimulation can be used to increase the flow frequency and velocity of the fluid in the fracture.On the one hand,the crude oil can be dispersed into small granular oil droplets to make the crude oil more easily imbibed and increase the imbibition speed and imbibition recovery degree.On the other hand,the small crude oil particles can be extracted under the action of drag force,so as to avoid the equilibrium of capillary force in pore channel and prolong the imbibition stability time.Based on the actual parameters of tight reservoir,a model was established to study the imbibition amount and stuffy well time,and the optimal stuffy well time was determined to be 5d through simulation results.