Testing the Combination of High Frequency Surface and Downhole Drilling Mechanics and Dynamics Data under a Variety of Drilling Conditions

摘要

Understanding the behavior of the drill bit, bottomhole assembly (BHA), and drillstring in drilling operations is difficult without accurate measurements of tensile load, torque, pressure, and various vibrations both at surface and downhole. A variety of methods have been employed to compress measurements obtained downhole in order to transmit them to the surface with measurement-while-drilling (MWD) mud-pulse telemetry. During the last ten years, some success has been achieved in making these measurements, recording them, and then retrieving the data at surface upon the end of the bit run. Meanwhile, the comparable measurements at the surface have limitations in terms of accuracy and calibration as well as dampening. An instrumented surface sub (ISS) has been developed that replaces the saver sub at the bottom of the top drive on a rig’s traveling assembly (Fig. 1). It measures in real time at the top of the drillstring, using accurate and calibrated sensors, tension/compression, torque, rotational speed in revolutions per minute (RPM), and surface pump pressure, among other parameters. These measurements, made at 400 Hz, are not dampened by the drill line and sheaves. A drilling mechanics module (DMM) sub that is part of the BHA has also been developed, which provides downhole measurements including, but not limited to, tension, torque, RPM, internal and annular pressure, at frequencies between 200 and 2,000 Hz. Additionally, along-string vibration measurements are provided using memory only devices. To evaluate both of these downhole and surface drilling data acquisition tools, a test was conducted in June 2010 at the Schlumberger directional drilling test facility near Cameron, Texas. Four different BHAs were run to evaluate downhole behavior and collect data using milled-tooth and PDC bits while directional drilling in surface rotary mode as well as with steerable motors. This paper presents some of the wide-range findings regarding the use and analysis of the data gathered in terms of static drilling mechanics, as well as dynamic drillstring behaviors and downhole vibrations.