西南石油大学学报(自然科学版)

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Research on Allowable Movement Speeds of Downward Drill Pipe in#br# Gasliquid Two Phase in MFC Drilling Operations

KONG Xiangwei1,2*, LIN Yuanhua2, HE Qiuyun3, QIU Yijie2   

  1. 1. School of Petroleum Engineering,Yangtze University,Wuhan,Hubei 430000,China
    2. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    3. Research Institute of Drilling & Production Engineering Technology,CCDC,Guanghan,Sichuan 618300,China
  • Online:2016-08-01 Published:2016-08-01

Abstract:

For the problems of allowable downward movement speed of drill pipe in gas-mud two phase during MFC drilling
operations,this paper establishes the semi-empirical model for allowable downward movement speeds of drill pipe at different
well depth by considering gas slippage,resistance between flowing phase and annulus wall,back pressure and pressure
difference in bottom hole. The variation characteristics of allowable downward movement speeds of drill pipe are acquired by
adopting the method of computer programming. The results show that when the drill pipe moving downward,increasing back
pressure will lead to the decrease of void fraction,increase of gas-liquid two-phase density and effective pressure imposed on
the bottom hole,which will further result in the decrease of allowable downward movement speeds of drill pipe. When the
gas influx rate in the bottom hole is increased,the pressure in bottom hole will be reduced to less than the formation pressure.
At that time,the allowable downward movement speeds of drill pipe can be increased because the increasing surge pressure
can eliminate a part of pressure difference between bottom hole and formation. The allowable downward movement speeds of
drill pipe should be decreased with the decrease of safety pressure difference. During the MFC drilling operation,the precise
calculation of allowable downward movement speeds of drill pipe can improve the effectiveness of drilling.

Key words: MFC drilling, gas-liquid two-phase, surge pressure, downward movement speed of drill pipe, gas influx rate

CLC Number: