Advanced High Frequency In-Bit Vibration Measurement Including Independent, Spatially Separated Sensors for Proper Resolution of Vibration Components Including Lateral, Radial, and Tangential Acceleration
Authors: Townsend Todd , Moss Will , Heinisch Dennis , Evans Kenneth , Schandorf Cecil 
Published: December 2021

Vibration measurement has become ubiquitous in drilling. Focus of drilling enhancement has expanded from traditional lateral and stick slip assessment to include torsional oscillations on motors, and high-frequency torsional oscillations (HFTO). Recent publications have highlighted the importance of these higher frequency measurements to analyze drilling dynamics and diagnose dysfunctions which can cause tool failures. A new vibration recorder will be presented which is capable of sampling at 2 kHz and higher to analyze non-linear transient dysfunctions.

Most in-bit vibration measurement options utilize a single unsynchronized triaxial accelerometer and low speed gyro. This design practice inherits specific challenges to the measurement and prevents the ability to decouple lateral from angular acceleration. Use of two sets of symmetrically placed (180 degree opposing) accelerometers has been in practice, but design constraints limit this approach to larger bits. Utilization of a new, outer diameter (OD) mounted vibration recorder for slim hole bits/BHAs with multiple spatially separated triaxial accelerometers, and a high-speed precision gyro will be described and evaluated with a comparison to other commercially available options.

Downhole vibration recorders have existed for over 20 years providing conventional drilling dynamics evaluation. These devices suffered from hardware limitations which constrained the customer to spaced out snapshots of time rather than continuous observation and required separate research modules to cover high frequency needs. This paper presents case studies utilizing a new vibration recorder which can cover these two customer needs in one device. Drilling Engineers desire a rapid turnaround macro view of synchronized downhole and surface data for offset well parameter optimization while research engineers desire a micro view with kilohertz range sample rate for a comprehensive understanding of all possible dysfunctions including HFTO, and high frequency shock, along with the capacity to research geology prediction techniques including fracture identification. Use of an advanced cloud-based software suite will be illustrated for a rapid high-level view of the full run with benchmarking capability of offset wells. Case study observations include stick slip identification covering 0 to above 600 rpm using a single gyroscope, and HFTO identification with accurate decoupling of tangential acceleration vs radial and lateral. Having the ability to satisfy both objectives with one device is new to the industry and presents a step change in capability.

A new, advanced vibration recorder is detailed which includes synchronized, spatially separated triaxial accelerometers, a triaxial shock sensor, a highspeed triaxial gyroscope, and temperature sensors. With 5 gigabytes of high temperature flash memory, more than 2 kHz sample rate for burst data and 1s period for downhole processed data, logged downhole recordings can cover greater than 200 hrs of drilling and may be available for analysis within minutes from drilling completion.