Research On Leakoff And Flowback Models Of Fracturing Fluid In Fractured Reservoir

Nowadays,hydraulic fracturing has become key technology to exploit unconventional reservoirs increasing production.Fracturing fluid leak-off in formation and Fracturing fluid flowback are general concerns of researchers,some scholars studied fracturing fluid leak-off and flowback at home and abroad.In view of existing theory model without considering the impact of stress sensitive effect and natural fracture to fracturing fluid leak-off;and the calculation of the settling velocity of the proppant has not considered the interference of the fracture wall roughness,and so on.This paper carried out intense research on fracturing fluid leak-off and flowback models of fractured reservoir.The main contents are as follows:(1)Fracturing fluid leak-off model considering stress sensitive effect are established about fractured low-permeability reservoirs based on Warren-Root dual-porosity model.The finite difference method is used to solve the model.Factors affecting leak-off were also studied based on the simulation,such as stress sensitive coefficient and so on.(2)Based on the principle of volume balance,the paper established fracture forced closure model with well friction loss and solved by Newton-Raphson method,Geological parameters and technological parameters affecting wellhead pressure change rule and fracture close time were analyzed.(3)The moment balance equation is established based on the principle of moment balance and the laws of sediment incipient motion,a critical velocity of the proppant flowback is obtained,considering the roughness of fracture surface and collision between proppants,the proppant subsidence rule in power-low fluid was analyzed,the fracturing fluid flowback critical velocity after and before fracture close was identified.(4)The corresponding relation between wellhead pressure and the size of choke is established,adjusting the size of choke dynamically according to the change of wellhead pressure.The effect of proppant's size,proppant's density and fracturing fluid viscosity after gel breaking to the size of choke through examples of calculation.Fracturing fluid and flowback models were discussed and improved in this paper,which is a kind of new method and has some guiding significance to the control of fracturing fluid leak-off and the optimization of flowback procedure.