欠平衡钻井环空岩屑对井底负压的影响

Effect of annular cuttings on negative pressure in under-balanced drilling process

对井下压力实测数据进行了分析,建立了环空岩屑影响井底压力增量的计算方法并编制计算软件,分析结果表明,环空岩屑对井底负压的影响很大.在4000～5000m的深井中,机械钻速高达10m/h时,环空岩屑引起的井底压力增量高达3～4MPa,甚至更高.因此,在深井井底负压值设计范围较小(0～2.5MPa)时进行井底负压控制,应该充分考虑环空岩屑对井底负压值的影响,针对不同情况采用不同的控制方法.该方法应用于大庆油田欠平衡设计计算和实钻,精确控制了井底负压,提高了大庆油田欠平衡钻井井底负压控制水平.

The pressure survey data in bottom hole were analyzed, and a computing method for annular cuttings effecting pressure increment in bottom hole was proposed. The responding calculation software was worked out. The analysis indicates that the actual annular cuttings in bottom hole have a great influence on the negative pressure at bottom. For deep wells of 4000-5000 meters in depth, when drilling rate is up to 10 meters per hour, the pressure increment in bottom hole resulted from annular cuttings is up to 3-4MPa and even higher. In order to control the negative pressure, the influence of annular cuttings should be considered. For different situations, the different control methods should be adopted. This methodology was applied to under-balanced calculation and negative pressure control in bottom hole in Daqing Oilfield. The negative-pressure control for under-balanced drilling in Daqing Oilfield was improved.