The Industry's First Real-Time Pseudo Gamma Measurements From an Instrumented Steerable Motor Using High-Frequency Drilling Dynamics Sensors

Abstract

Downhole drilling motors are the workhorse of our industry and are used on almost every land well drilled globally. This makes an instrumented drilling motor the perfect tool for geosteering with near-bit inclination, drilling-dynamics and formation-identification sensors. Already proven drilling motor technology has been upgraded with miniature embedded sensors to provide real-time continuous inclination, advanced drilling dynamics, and pseudo-formation-identification data. The sensors are sized to mount into existing drilling motor components without adding length or compromising the mechanical integrity. The high-frequency drilling-dynamics measurements, including lateral vibrations, axial vibrations, stick-slip, high-frequency torsional oscillation (HFTO) and motor back-drive dynamics are measured in the motor. The sensor unit applies advanced signal processing routines to the high-frequency vibration measurements downhole and converts the vibration data into pseudo gamma (pGamma) measurements, which have been correlated with measurement-while-drilling (MWD) gamma measurements in lateral wellbores. pGamma can alert the driller as soon as the bit starts cutting new formations, as compared with traditional real-time gamma measurement, which is about 40-50ft away from the drill bit. In addition, the sensor units measure bit and string rotation speeds below and above the mud motor, enabling the detection of the motor output rotation speed and motor back-drive dynamics in real time. Real-time near-bit inclination, advanced drilling-dynamics and geosteering measurements have been provided in a mud motor without compromising mechanical integrity or directional response. The real-time inclination, drilling dynamics data, and pseudo-gamma measurements from the instrumented motor are integrated into our drilling advisory system to enhance the drilling efficiency and wellbore placement accuracy.