GCAAT Drop Gyro Case Study - Gyrodata Incorporated€¦ · The gross error was a result of an...
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Problem An Operator approached Gyrodata to inquire about options for verification of the last 1,500ft of a horizontal well due to questionable data from the MWD with a close approach to a lease line. Solution It was decided to run GCAAT (Gyro Compassing All Attitude Tool) in drop memory mode. The tool would be pumped through the pipe and down to the BHA. The tool will survey while tripping out of the hole at each stand providing gyroscopic Inclination and Azimuth for each depth surveyed. Typically this feature is activated with the GWD system already part of the BHA where real time GWD data is transmitted along with MWD data while drilling the section (s) for wellbore positioning data. The Memory Multi-Shot mode is activated at the end of the run to verify the real time data as well as obtain gyroscopic surveys where previously only MWD data was collected. This feature saves considerable rig time and provides true well bore positioning data for the entire wellbore. The client had only used a MWD system for positioning data and had no other means to verify well- bore position in real-time or to detect gross errors. Since the client had a section with questionable MWD data, it was decided the GCAAT system would survey the entire well- bore to provide proper positioning data. The tool was pumped down to the BHA at the end of the lateral section. The system was used to survey from 14,365 feet back to surface. Result Once the data was processed at surface, a comparison was made to the MWD data. The GCAAT detected a gross error not just for the section with questionable data but for the entire wellbore. The gross error was a result of an incorrect MWD declination correction value, which led to a difference of 5.64 degrees of Azimuth for each survey station record- ed by the MWD. (see figure 1.) The correct declination was then applied to the MWD. This brought the MWD azimuth closer to the GCAAT data. (see figure 2.) The gross error in the MWD azimuth led to a difference of 415ft in the easting compared to the GCAAT data. (see figure 3.) The client was significantly over their lease line. They decided to plug back and sidetrack at a future date. If the GCAAT had been run earlier or GWD90 had been run in real time with the MWD, the client would have benefited from detecting this gross error as well as having two independent surveying instruments to verify true wellbore position. GCAAT Drop Gyro Survey
Transcript of GCAAT Drop Gyro Case Study - Gyrodata Incorporated€¦ · The gross error was a result of an...
ProblemAn Operator approached Gyrodata to inquire about options for veri�cation of the last 1,500ft of a horizontal well due to questionable data from the MWD with a close approach to a lease line.
SolutionIt was decided to run GCAAT (Gyro Compassing All Attitude Tool) in drop memory mode. The tool would be pumped through the pipe and down to the BHA. The tool will survey while tripping out of the hole at each stand providing gyroscopic Inclination and Azimuth for each depth surveyed. Typically this feature is activated with the GWD system already part of the BHA where real time GWD data is transmitted along with MWD data while drilling the section (s) for wellbore positioning data. The Memory Multi-Shot mode is activated at the end of the run to verify the real time data as well as obtain gyroscopic surveys where previously only MWD data was collected. This feature saves considerable rig time and provides true well bore positioning data for the entire wellbore. The client had only used a MWD system for positioning data and had no other means to verify well-bore position in real-time or to detect gross errors. Since the client had a section with questionable MWD data, it was decided the GCAAT system would survey the entire well-bore to provide proper positioning data. The tool was pumped down to the BHA at the end of the lateral section. The system was used to survey from 14,365 feet back to surface.
ResultOnce the data was processed at surface, a comparison was made to the MWD data. The GCAAT detected a gross error not just for the section with questionable data but for the entire wellbore. The gross error was a result of an incorrect MWD declination correction value, which led to a di�erence of 5.64 degrees of Azimuth for each survey station record-ed by the MWD. (see �gure 1.) The correct declination was then applied to the MWD. This brought the MWD azimuth closer to the GCAAT data. (see �gure 2.) The gross error in the MWD azimuth led to a di�erence of 415ft in the easting compared to the GCAAT data. (see �gure 3.) The client was signi�cantly over their lease line. They decided to plug back and sidetrack at a future date. If the GCAAT had been run earlier or GWD90 had been run in real time with the MWD, the client would have bene�ted from detecting this gross error as well as having two independent surveying instruments to verify true wellbore position.
GCAAT Drop Gyro Survey
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GCAAT Drop Gyro SurveyCont.
