Abstract
High friction of the drill string against the wellbore has become a concern in the process of drilling, irrespective of whether it is a vertical, directional or horizontal application. This source of additional torque and drag will lead to low rates of penetration, poor tool face control, short runs, severe drill string and bit wear, and at the same time, could cause problems while running casing, liners and completions. In directional and horizontal applications, this high friction could also lead to high well tortuosity, which will limit the amount of step out and can even impair productivity.
The implementation of a unique tool, referred to as a Drilling Agitator Tool (DAT), has demonstrated clear improvement in drilling performance by reducing stick slip and torque at the drill string. This has enabled reduction in drag and thus improved weight transfer to the bit when drilling through highly interbedded formations, directional applications or long horizontal sections. It has also shown greater accuracy in maintaining tool face control once the static friction was minimized. This DAT relies on three main mechanisms: a power section, a valve and bearing section, and an excitation section. The tool operation vibrates the drill string with a low frequency and low amplitude axial vibration.
This paper illustrates case studies from the Haynesville, Fayetteville and Barnett Shale Plays, where the DAT has proven to help reduce torque and Stick-Slip when run on rotary in vertical applications, as well as Motor assemblies through directional and horizontal sections. These improvements in drilling performance have resulted in longer runs and faster rates of penetration compared to offset wells, thus reducing the number of bits and improving the economics in drilling these shale plays.
