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.
Read the synopses in the February 2012 issue of JPT.
Stéphane Menand, SPE, is Managing Director of DrillScan US. Previously, he held a research position at Mines ParisTech University. Menand has 14 years of experience as an R&D project manager in drilling engineering–more specifically in directional drilling, drillstring mechanics (torque, drag, and buckling), drilling dynamics, and drill-bit performance. He has authored several SPE and other technical papers and holds several patents. Menand earned a PhD degree in drilling engineering from Mines ParisTech University. He serves on the JPT Editorial Committee, the SPE Books Development Committee, and the SPE Drilling and Completions Advisory Committee.