Development and service of drilling fluid

 We started service on the well after running of 324 mm casing. During the first month was drilled more than 700 m. The footage was proceeding, there were no complications. But, at a depth of 3463 m, we faced a serious geological complication - catastrophic circulation losses.  Bridging pills were ineffective. It was necessary to saturate entire volume of the drilling mud with the bridging agents, this allowed quickly restore well drilling.

 The presence of bridging agents in the drilling mud precluded the possibility of its cleaning from cuttings by shale shakers. Attempts to partially cleaning the drilling mud were failed. After 3-4 cycles of circulation losses were resumed and it was necessary to add a fresh portion of the bridging agents into the mud system. Therefore, drilling mud was cleaned only by centrifuges and hydrocyclone units. The density of the drilling mud was maintained in the range of up to 1200 kg/m3.

  An additional complication in the way of deepening the well was the zone of spalling rocks. The traditional method of drilling in such deposits provides for increase in mud density and creating overpressure on the walls of the well. However, in this case, such method was unsuitable due to the presence of lost-circulation formation. Therefore, drilling mud was continuously treated with softening inhibitors reagents. Eventually, the interval was successfully drilled with minimal loss of drilling mud and casing ran to the bottom..

 Now we are preparing for the drilling fluid replacement. The next interval with the AHFP, the necessary mud density 1860 кг/м3.