Early borehole uncleanness identification based on PWD tool in highly deviated extended-research wells

The borehole of highly deviated extended-research wells are usually caused to be unclean for the long horizontal segment and high deviation of such wells.For this reason,downhole annulus pressure originating from using PWD tools is proposed to identify the early borehole unclearness.The cause of borehole uncleanness is firstly analyzed in this paper.Later the variations of downhole annulus pressure are presented as the borehole is unclean.Comprehensive borehole uncleanness identification is carried out based on the difference identification between experimental annulus pressure and its theoretical calculation and the probability density identification of annulus pressure.According to the theoretical analysis,the relevant calculating procedure is worked out and the real data acquired from an extended-research well is calculated on the site.Relevant measures are adopted according to the general index of borehole uncleanness identification.It proves that the method is credible in early borehole uncleanness identification.