Vertical Drilling Technology: A Milestone in Directional Drilling

TLDR

The KTB program seeks to investigate deep continental crust conditions by drilling a 10 km borehole, requiring minimized drag, torque, and casing loads to ensure safe operation. A unique vertical drilling system (VDS‑5) equipped with an external negative steering device, high‑temperature sensors, and hydraulic/mechanical components allows drilling to 8 km while keeping borehole inclination under 1° despite 60° foliation dip, as demonstrated by over 80 successful runs. At 6.7 km depth the system achieved only 4 m horizontal drift and drag below 120 kN, indicating that the VDS‑5 can support future closed‑loop directional drilling guided by preprogrammed paths or formation‑evaluation sensors.

Abstract

ABSTRACT The Continental Deep Drilling Program of the Federal Republic of Germany (KTB) is a fundamental research project to investigate the physical and chemical conditions and processes in the deep continental crust. To meet the geoscientific goals, it is necessary to drill an ultra deep borehole with a target depth of 10000 m. To reach this depth safely it is necessary to minimize the drag and torque for the drill string as well as the loads on the casing strings. Therefore a unique drilling concept has been set up including the application of automatic Vertical Drilling Systems (VDS). The latest development VDS-5 has an external negative steering device. Sensors, electronics, electric power supply and all hydraulic and mechanical parts are designed for an operating temperature environment up to 200°C (390°F) or a depth equivalent to 8000 m. Applying the vertical drilling technology an average borehole inclination of less than 1° could be maintained under a foliation dip of about 60°. At a depth of 6700 m the horizontal displacement was only 4 m. Drag forces could be kept to values less than 120 kN. Drilling results from more than 80 runs with the vertical drilling systems are reported. These results promise various options for further development, such as an automatic closed loop drilling system for general directional drilling applications. This system could be steered either along a preprogrammed well course or with the incorporation of formation evaluation sensors, working in formation boundaries.