Development and service of drilling fluid

The well was drilled to a depth of 4130 m two months ago, but the preparation of the wellbore for the casing running and geophysical work was delayed for a long period. The difficult S-interval profile, intensive keyseating and numerous correction runs were appeared. Despite of slight deviation from the vertical, only 125 m, the movement of the drill tool in the curvature intervals was accompanied by tightening and landing. Therefore, despite the high stability of the wellbore, there was a need for borehole reaming with a gradual increase in the stiffness of BHA.

There were significant problems with the geophysical well logging. Geophysical instruments did not reach bottomhole as a result of key seats in the intervals of intensive curvature. Well logging was made with the use drilling pipes.

After analyzing the geophysical data and estimating the zones of possible risks the well was prepared for casing running. The top drive was a major factor which allowed running with rinsing and rotation. As a result, the casing was set to the bottomhole by one section and successfully cemented.

The great achievement in the successful completion of this extremely difficult stage of work belongs to the clayless drilling mud Biocar-MT, which allowed to prevent caving and provided the effective cleaning of bottomhole from cuttings. The content of potassium chloride in the drilling mud was maintained at a level of 6-7%. Polyglycol was added into the system periodically.

According to the experience of drilling in this area, it is expected to open the zone of unstable argillites with abnormally high formation pressure in the interval of 4130-4285 m. In order to prevent rocks from caving, it is necessary to increase the density and provide high extraction properties of the drilling mud. Further drilling will be carried out on the clayless drilling mud Biocar-MT with a density of 1340 kg / m 3 .

  • Density – 1,19 g/сm3;
  • Funnel Viscosity – 75 seс;
  • Gel – 120/134 dPa;
  • PV – 14 cP;
  • YP – 215 dPa;
  • Filter Loss – 5,5 сm3/30 min;
  • Salinity – 10,8 %;
  • KCl – 6,8 %;
  • рН – 9,0.