Lingshui X-1 block is located in ultra-deepwater region in western South China Sea. Drilling in this area are encountering many technical problems, such as low temperature, poor lithology in shallow formation, low fracture pressure gradient, gas hydrate and shallow geological hazards, which bring great technical challenges to subsea wellhead stability (Yang et al., 2013). In order to ensure wellhead stability and improve top-hole operation efficiency, jetting technology was used for spud-in. First of all, carrying capacity curve of structural conductor was obtained from mechanics analysis of shallow seabed soil in Lingshui X-1 block. Secondly, structural conductor size selection and load analysis were carried out to determine safe setting depth of structural conductor in Lingshui X-1 block. Finally, bit stick-out, bit size selection, Weight on Bit (WOB) and pump rate were optimized on the basis of comprehensive analysis of ultra-deepwater under top-hole jetting technology and BHA characteristics. Well LSX-1-1 was taken as an example to illustrate field operation for top-hole jetting. This successful case of top-hole jetting technology in Lingshui X-1 block of western South China Sea could provide technical guidance for future drilling activity in similar ultra-deepwater wells.

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