Analysis of prediction methods of pressure decrease under drill bit while pulling-out drilling tool

Abstract

The analysis of existing surveys associated with the occurrence of gas shows in the well drilling, for the elimination of which a great amount of cost and time spent has been carried out. The most widespread of them are the complications of gas shows while pulling-out of drilling tool from the well. It was revealed that to prevent such complications, it is necessary to reduce the pressure of drilling mud under the bit of pulled-out drill stem from the well. Existing methods of reducing the fluid pressure under the drill bit of a pulled-out drilling tool lie in the fill-up of drilling mud through the borehole annulus with special fill-up devices. Therefore, the fill-up is conducted through various quantities of pulled-out flares. Considering this, we offer a method of specification of reducing fluid pressure under the bit of pulled-out drill stem via squeezing the drilling mud through the drilling tubes. The fill-up period is defined from the graphics of continuous changes of shearing strength in time obtained during the periodic deterioration of structure in the moments of a maximum value of shearing strength via stirring the drilling mud in shearing rates corresponding to the speed of pulling-out of drilling tool. The maximum value of the shearing strength is specified via the dependence provided