A Successful Experience in Using Short Gauge PDC Bits for Drilling with Point-the-Bit Rotary Steerable Systems under Geological Conditions of Verkhnechonskoye Field

Abstract

The investigations, conducted by many companies, show that a long gauge PDC bits, which are used during operations with "point-the-bit" Rotary Steerable Systems (RSS), allows for mitigating the bit vibrations and improve steerability.

But in this paper, we shall present the usage of the short gauge PDC bits when drilling with this type of RSS in a pay zone, which is characterized by hard streaks.

More tight shaled-out interlayers were encountered in pay zone when developing a peripherical part of Verkhnechonskoye field.

On the boundary of the rocks of different hardness a number of formation "pushes" (short intervals with a sharp change of the inclination) increased significantly. A continuous operation in the formation "push" intervals resulted in downhole equipment damages.

When conducting kick-off operations in an open hole in multilateral wells with the use of "point-the-bit" RSS and the long gauge bits a quantity of failures reached 60 %. For that reason, it was necessary to kick off using a BHA with a downhole motor; but in this case additional runs are required.

A hypothesis was made that the usage of short gauge PDC bits will help to promptly correct the wellbore trajectory when formation "push" occurs, as well as allow for drilling a few laterals over one run.

Deviation from the standard design made it possible to reduce a number of runs when drilling multilateral wells, increase an average rate of penetration and significantly reduce frequency of Dogleg Severity exceedance events when passing through hard streaks.