Study On Preventing And Plugging Lost Circulation Technique In Daqing Yingtai Area

Lost circulation, which is a common problem in drilling engineering, may result in waste of drilling time and drilling fluid lost, and lead to a series of complicated situations, such as sticking, blow out and cave in etc.. More severely, the well drilled has to be abandoned. This will cause economic loss. Lost circulation affects drilling severely and it is a problem that many foreign and domestic researchers in drilling engineering pay much attention to. Because of the complicated reasons and restricted factors of lost circulation, it has not been solved by the researchers in drilling engineering till now.Lost circulation subjects to objective and subjective factors. The existing of pores and fractures in formation is the first reason of lost circulation, and the excessive high density of drilling fluid will give more opportunity to lost circulation. On terms of preventing lost circulation, the drilling fluid used must be in reasonable density and strong inhibition. The relations between lost circulation and inhibition was not known before, and the density of drilling fluid was paid much attention while the surge pressure in tripping in was ignored. This makes the reasons of lost circulation cannot be analyzed objectively and the sound measures to it cannot be set.Based on the geological features of Daqing Yingtai area, the preventing and plugging lost circulation technique is systemically analyzed on both mechanical sides and chemical sides. The calculation model of well bottom surge pressure is built and the cave-in-preventing drilling fluid is developed. The drilling fluid used in this area has been adjusted and a whole set of measures for cave-in-preventing, lost-circulation-preventing and leakage-plugging is make, which is based on the analysis of the lost circulation reasons of Daqing Yingtai area, lab evaluations of plugging agents and development of chemical plugging agent The on-site experiments are done and the result is satisfied and the lost circulation problem in this area is solved successfully.