Field test of simultaneous gyro attitude reference for magnetic ranging measurements in a near vertical magnetically perturbed environment

Transcription

1 Field test of simultaneous gyro attitude reference for magnetic ranging measurements in a near vertical magnetically perturbed environment Georgy Rassadkin Scientific Drilling International September 2017

2 Agenda Introduction What is magnetic ranging? How is gyro attitude referencing done? Field test #1. Solenoid based ranging system Field test #2. Rotating dipole at bit while drilling ranging system Summary of results

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4 Georgy Rassadkin. Biography M.Sc., Applied Geophysics, Dubna International University 7 years in gyro and MWD surveying and magnetic ranging Currently work as a training instructor in Scientific Drilling International in Houston

5 What is magnetic ranging? Using a magnetic field (other than the Earth s field) to determine the distance and direction between wellbores Source A magnetic field generator (solenoid, rare earth magnet, current on a wire or casing) Receiver MWD magnetometer package Wireline magnetometer package

6 Why gyro attitude referencing? NORTH From prior survey: Inc = 40 deg Azim = 90 deg From tool: Inc = 40 deg Azim is BAD AzTF(MTF) is BAD HSTF = 90 deg DOWN Tool highside From prior survey: Inc = 0 deg Azim =??? From tool: Inc = 0 deg Azim =??? AzTF(MTF) is BAD HSTF =??? Calculated: AzTF = Azim + HSTF =? +? =??? Calculated: AzTF = Azim + HSTF = = = 180 deg AzTF (GyTF) = 180 deg

7 How is gyro attitude referencing done? North-seeking gyro is included into a ranging receiver assembly All sections are rigidly connected All sensor packages aligned to the same tool highside True North gyro data (Inc, Azim, AzTF/GyTF, HSTF) and magnetic ranging data collected and processed together

8 Field test #1. Solenoid based ranging system Two vertical wells Client requested 4.7m +/-0.65m separation at TD (~500m) Well #2 gyromwd Well #1 MWD 2m 8m Conventional survey accuracy +/-3m at TD Ranging accuracy +/- 0.15m

9 Field test #1. Gyro orientation vs magnetic orientation Magnetic orientation is inaccurate due to interference from nearby casing Gyro is not affected by the magnetic interference

10 Field test #1. Gyro orientation vs magnetic orientation Grey reference well Red magnetic oriented ranging shots Blue gyro oriented ranging shots

11 Field test #1. Gyro orientation vs magnetic orientation Travelling cylinder m MD Blue gyro oriented ranging Red magnetic oriented ranging

12 Field test #1. Simultaneous gyro referencing gives 10x improvement of ranging accuracy The spread of magnetic oriented ranging shots is large (on the left) Gyro orientation provides consistent ranging results (on the right)

13 Field test #2. Rotating dipole at bit while drilling ranging The objective was to safely pass by a vertical well while drilling a horizontal well in close proximity 2 sigma uncertainty for the MWD surveys at horizontal was too large The normal industry practice is to use prior survey and the tool highside for ranging orientation

14 Field test #2. Simultaneous gyro orientation vs interpolated prior survey Azimuth interpolated to the sensor depth from a previous survey fails to provide accurate NEV orientation at vertical North-seeking rate gyro rigidly connected and aligned with ranging assembly solves this problem vertical well with the ranging assembly inside ranged position oriented via: simultaneous gyro interpolated prior survey OWSG MWD+IFR2+MSA

15 Northing, m Field test #2. Simultaneous gyro referencing multiplies ranging accuracy Accuracy improved over 2.5 times comparing to previous method Simultaneous Gyro Orientation Orientation from interpolated prior survey Easting, m Horizontal scatter of the vertical well position near the pass by derived from the MWD surveys plus ranging shots at the total separation of 50m and less -692

16 Summary of results Contemporaneous gyro measurements can improve magnetic ranging accuracy by up to 10-fold over previous methods The described technique is an effective solution when magnetic ranging performed in vertical magnetically perturbed environment The applications for the described technique include o relief well drilling o plug and abandonment o collision avoidance/risk mitigation o civil and mining projects

17 Thank you! Questions?