Technology Focus: Drilling Technology (February 2012)
Authors: Menand Stephane 
Published: February 2015

Technology Focus
Since the first downhole electric measurement was made in 1927 by the Schlumberger brothers (first electrical-resistivity well log), the oil/gas industry has been striving to develop and improve new tools and sensors for downhole measurements. Indeed, these sensors aim at measuring many parameters, such as physical properties of rocks and fluids (formation evaluation), wellbore position (inclination and azimuth), or downhole drilling-mechanics conditions. Over the last 12 months, I have been impressed by the number of papers and news articles dealing with drilling mechanics and with vibration-data measurement, transmission, processing, and interpretation. Dynamics and vibration events still are responsible for high nonproductive time (NPT) (e.g., tool failures in many cases) and suboptimal drilling performances. With advances in electronics components, tool reliability, battery technology, and sensors, many companies have begun to develop their own memory-based drilling-measurement tools and to offer the associated service (data processing and interpretation) to operators to maximize drilling efficiency and, thus, reduce NPT.
These downhole drilling-mechanics-measurement tools, rated up to 150°C, generally integrate the following sensors: bending moment, vibration (three-axis accelerometers), weight on bit, torque on bit, annular pressure, temperature, and magnetometers (downhole rotational speed). Data are stored in a memory-based subassembly powered by a lithium-based battery (capacity up to 200 hours), or are transmitted to the surface (by use of mud-pulse, electromagnetic, or wired-pipe telemetry). The latest developments include ingenious sensors placed in the pin of the drill bit (avoiding an extra subassembly in the bottomhole assembly). Though measurements originally were captured close to the bit in the bottom portion of the drillstring, the industry has identified the need to have multiple sensors deployed all along the string (from the bit to the topdrive) to monitor continuously and anticipate any drilling event.
This outbreak of downhole-sensor technology is good news for the industry because it will probably accelerate the understanding of what is happening downhole even more, thus improving the overall drilling efficiency. Downhole drilling measurements should not be limited to only high-cost environments, but should be used in the early stage of the field development to accelerate the learning curve and, thus, optimize the drilling process for the next wells. Even though some downhole drilling and dynamics tools were developed in the 1980s, the industry now has more-accurate sensors, better physical models, and more computational power to process and analyze this huge amount of drilling data.
Recommended additional reading at OnePetro: www.onepetro.org.
SPE 146561 Mitigation of Torsional Stick/Slip Vibrations in Oilwell Drilling Through PDC-Bit Design: Putting Theories to the Test by Jayesh R. Jain, SPE, Baker Hughes, et al. (See JPT, December 2011, page 79.)
SPE 140347 Testing the Combination of High-Frequency Surface and Downhole Drilling-Mechanics and -Dynamics Data Under a Variety of Drilling Conditions by Bill Lesso, SPE, Schlumberger, et al.
OTC 21506 Buildup Construction in Salt Formations by Renato Amaro, Petrobras, et al.
SPE 140317 Extension of Gauge Length To Reduce Vibrations and Improve Drilling Performance by Gregory F. Smyth, SPE, Hibernia Management and Development, et al.