Weighted averaging of overlapping surveys will improve the estimate of the wellbore position and reduce the position uncertainty. An existing, rigorous method describes how the optimal weight factors can be achieved. However, the rigorous method is not commonly used, because of the complexity of the data management and processing.
We have developed a procedure for creating a combined instrument performance model (IPM) file that directly yields the reduced uncertainty of the averaged surveys, when it is applied as input to standard position error analysis. This represents an important step towards simplification of the rigorous procedure. Comprising inclination- and azimuth-dependent weight factors, one such file may be valid for any wellbore profile at any direction, and over an entire oil field. This is demonstrated in the paper for various synthetic well profiles, through comparison with results obtained by the rigorous averaging procedure.
The combined IPM file facilitates the simultaneous use of all available survey information in a consistent way. This may yield significant improvements to the wellbore position accuracy. Furthermore, the new procedure may help in the construction of instrument performance models for new survey tools that incorporate fixed combinations of sensor packages, which may result from recent years’ development of solid state sensors.
Number of Pages
Chia, C. R., Phillips, W. J., and Aklestad, D. L. 2003. A New Wellbore Position Calculation Method. SPE Drill & Compl 18 (3): 209-213. SPE-85111-PA. http://dx.doi.org/10.2118/85m-PA.
Ledroz, A., Bang, J., and Weston, J. 2016. New Instrument Performance Models for Combined Wellbore Surveys: A Move Toward Optimal Use of Survey Information. SPE Drill & Compl 31 (4): 307-316. SPE-178826-PA. http://doi.org/10.2118/178826-PA.
Lowdon, R., Igarashi, J., and Sargin, D. 2017. Solid State Gyro While Drilling Technology Provides Accuracy and Robustness. Presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 9-11 October. SPE-187220-MS. http://doi.org/10.2118/187220-MS.
Weston, J. and Ledroz, A. 2019. Combined Gyroscopic and Magnetic Surveys Provide Improved Magnetic Survey Data and Enhanced Survey Quality Control. Presented at the SPE/IADC International Drilling Conference and Exhibition, The Hague, The Netherlands, 5-7 March. SPE- 194130-MS. http://doi.org/10.2118/194130-MS.
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