Application and evaluation of unimpeded anti-fouling efficient flushing string

The blocks with high wax content in Liaohe Oilfield are suffered from easy wax precipitation on pipe strings, low thermal flushing efficiency and reservoir contamination due to well flushing, which are the key factors restricting the efficient development of vulnerable oil reservoirs with high wax content and low pressure coefficient. To deal with these difficulties, open-flow anti-fouling flushing string technology was studied. The pump leakage control device was developed. Based on the design of floating position valve in this device, open flow of the liquid produced from oil layers is realized in the process of lifting and lost circulation can be controlled and prevented from invading into low-pressure oil layers in the process of wax removal and well flushing. In addition, the technical difficulties of tubing creep and poor sealing time efficiency can be avoided effectively based on the collaborative application of tubing anchor, tubing centralizer and self-sealing packer. Field test and pilot test show that the average flushing time per well is decreased by 53.4%, the average flushing fluid consumption per well is reduced by 53.9% and the average productivity recovery time per well is cut down by 112.8 h. In conclusion, this technology can effectively increase oil well productivity and well flushing efficiency and avoid pay zone contamination, and it provides one effective way for the development of vulnerable oil reservoirs with high wax content and low pressure coefficient.