Development Of Precrosslinked Gel As Lost Circulation Curing Agent

Lost circulation is one of the complicated downhole problems during the drilling engineering. The bridging particle is used popular as lost circulation curing agent (LCM).This LCM often perform poorly in the controling filud lost because of the poor deformability and Water-swelling capacity. The plugging is difficult that conveniional lost circulation materials often perform poorly because of high water salinity, big-leakage passage and high temperature.In order to ensure drilling security and effieieney,reduce constrction cost,it is very significant to study the precrosslinked gel to curing lost circulation .Comparing with convenional precrosslinked gel, this new precrosslinked gel have suitable swelling ability ,heat resistance,high tensile strength and salt tolerance. The capacity of resistance to temperature of this series of precrosslinked gel is above 120℃.Especially the precrosslinked gel YNJ-3 and YNJ-4 anti temperature capacity can up to 150℃. The samples still have high tensile strength,fine condensability,high spring-back rate and good flexibility after swelling in water at 150℃.Based on the precrosslinked gel theory and performance,we do the experimental researehes on the precrosslinkedgel plugging properties.The experiment results showed that the precrosslinked gel have good compatibility with drilling fluid. The precrosslinked gel LCM sealed the permeable sands effectively with the maximum bearing pressure reaching 9.0 MPa. The results showed that pH value of the drilling fluid and formation water salinity don't have big influence on plugging ability of precrosslinked gelAccording to the migration process this paper analyzes the plugging mechanism of this LCM.Sum up the precrosslinked gel LCM congtrol lost circulation by bridging role, the role of expansion plug, skeleton structure supporting and chemical cementation layer.