关键词: 高密度钻井液, "Ｕ"型管效应, 复合钻具, 起钻过程, 流动规律, 环空灌浆量

Abstract:

Before tripping on the drilling site, it is necessary to pump into the nozzle of the drilling tool with a higher density drilling fluid than the circulating drilling fluid. Higher density drilling fluid can balance the pressure loss and the pressure difference between annulus and nozzle caused by drilling cuttings. However, the height difference of higher density drilling fluid with different volumes in different drilling nozzles will cause the flow of drilling fluid in the nozzle-annular space because of the U-tube effect, which will affect the judgment of complex well conditions such as overflow and lost circulation, especially in the use of compound drilling tools in deep and ultra-deep wells. This paper analyzes the pressure change and flow law of the nozzle-annular drilling fluid system that is affected by the U-tube effect during compound drilling tool tripping operations after pumping higher density drilling fluid. The results show that during the tripping out process of the compound drilling tool, the annulus pumping amount appears as "normal-lack-exceed-normal-exceed pumping" during the whole tripping out process. There is a positive correlation between the abnormal pumping, the ratio of pumping anomaly distance to nozzle volume per unit length of large and small drilling tools, the density difference of higher density drilling fluid and drilling fluid in hole, and the back pre higher density drilling fluid; U-tube effect; compound drilling tools; tripping; flow law; annular pumping amount higher density drilling fluid; U-tube effect; compound drilling tools; tripping; flow law; annular pumping amount higher density drilling fluid; U-tube effect; compound drilling tools; tripping; flow law; annular pumping amount higher density drilling fluid; U-tube effect; compound drilling tools; tripping; flow law; annular pumping amountssure as pump stopped. The theoretical calculation results can provide guidance for monitoring of pressure in the well, which is especially of great significance for determining the occurrence of overflow and loss and other complex situations in the deep and ultra-deep wells.

Key words: higher density drilling fluid, U-tube effect, compound drilling tools, tripping, flow law, annular pumping amount