HIGH DENSITY DRILLING FLUID TECHNOLOGY FOR WELL KAI-2 IN QINGHAI OILFIELD

The geological condition is very complex in Katmerica structure of Qinghai Oilfield, due to the existence of high-pressured slat water layer, long section of gypsum salt zone, and interlayer existing of high pressure and low pressure at the same time.Drilling was extremely difficult as hole collapses were likely to happen in the upper oil-sand group containing long section of shale, while such problems as lost circulation, well kick, hole sloughing and formation water frequently took place in the lower oil-sand group;furthermore, the deep groups were never penetrated by offset wells, thus there was no geological information available.High density polysulfonated drilling fluid was used in well Kai-2, to control and solve the problems of blowout, lost circulation, hole collapse, pipe sticking, high temperature and slat water, as well as to stabilize the bore wall.