Treatment of ultra high-pressure brine overflow by drainage brine with controlling pressure technology

Overflow of high -pressure brine causes stratification and sedimentation of drilling fluid, which damages the performance of drilling fluid and lead to serious accidents such as sticking. In the face of saltwater overflow, the common practice is to increase the density of drilling fluid to prevent and deal with it. However, increasing the density will lead to serious lost circulation in the thief layer, thus aggravating the saltwater overflow. In order to solve this problem, this paper puts forward a method of drainage brine with controlling pressure to deal with the overflow of high -pressure brine layer. Through laboratory experiments, the pollution capacity limit of high -pressure brine on oil-based drilling fluid was determined, and the drainage brine with controlling pressure technology was systematically proposed. The controlled pressure water drainage treatment technology has been successful applied in 4 Wells drilling in ultra- deep salt paste formation in Tarim Basin.