RESEARCH ON ANTILEAKAGE CEMENT SLURRY FOR ADJUSTMENT WELLS IN DAQING OILFIELD

Great changes occurred in formation pressure because of long-term waterflooding in La, Sa and Xin oilfield of Daqing. So high-pressure zone and under-pressure zone exist in one well simultaneously, as a result, lost circulation is very easy to occur during drilling and cementing. Antileakage cement slurry technology for adjustment well can improve rheological and cementing performance by using additives. Experiment in 5 aspects were carried out:1. Conventional physical performance; 2. Rheological performance; 3.Expansion and interface strength; 4. Free water; 5. Anti-water breakthrough performanc e. The experiment showed:the indexes of DFL cement slurry were better than those of cement slurry without additives. And concluded:1. DFL antileakage cement slurry with low frictionaI resistance had good rheological performance and low critical flow rate. Low-speed turbulent flow displacement was easy to be obtained. Under the same condition, the frictional resistance was 74% lower than that of the original slurry, the pumping pressure of displacement on-site can be decreased by 1MPa. 2. DFL cement slurry was stable and no free water separated out. 3. The compression strength and interface strength are increased than before, the cement slurry had a certain expansion and anti-water breakthrough performanc e. 4. A little additives were required and wet mixing was adopted, so it was easy to be used on site.