Research Of Hydraulic Fracturing Flowback Optimization Design

Fracturing fluid flowback is an important part of the hydraulic fracturing operations. Thisprocess occurred during the fracture closure. However，we can’t grasp the situation aboutcrack closure during the well shutdown or flow back process after fracture closure、fracturingfluid leadoff，so it’s often seem to have no basis to control the flowback rate. Thus，the paperestablished a flowback model of fracturing fluid to judge if it can flowing flowback afterfracturing，and calculated bottom hole pressure，on way resistance，perforation friction andcrack friction，got the judging condition of flowing flowback of fracturing fluid and theduring time to flowing flowback. During the flowing flowback phase，obtained the wellheadpressure of natural closed and forcing closed，combined with the flowback quantities offracturing fluid，the flowback quantities of proppant，and fracturing fluid’s critical flowbackrate to achieve a dynamic optimization about the blowout choke diameter of the process. Thefast flowback rate will lead to a large number of proppant reflux．The slow flowback rate，will make fracturing liquid damage the formation because of the retention time is too long，thus appropriate flowback procedures usually is a key to keep good flow conductivity. Afterthe flowing flowback phase，lay down gas lift valve to help flowback，then define theequilibrium point of casing and tubing to get the setting depth of the gas lift valve’s final stageby calculating the pressure distribution of fracturing string and annulus，and take the depth asthe judgment of the end of the gas lift design. Through the judgment，calculate the lay downseries of gas lift valve and the parameters of each gas lift valve according to the air injectingpressure and target delivery rate，then get the required parameters of gas lift flowback. Withthe development of fracturing techniques，the unceasing increase in fracturing well depth， inthe treatment of fracture，energy of refactoring formation is constantly decreasing，rely onlyon the flowback rate of blowing，fracturing fluid can’t meet the requirements of constructionsite.