This article focuses on the industry standard MSA correction implemented in our free solutions: MWD STD Basic, an automated cloud platform, and MWD STD MSA, a standalone application. But we also have MWD STD Advanced, an automatic multi-user survey management platform, that uses the Novel MSA correction with improved accuracy.
Unlike MWD STD Advanced implementing the Novel MSA algorithm [1], which is more accurate and robust, MWD STD Basic uses the conventional MSA algorithm proposed by Brooks in [2] and modified by Hanak in [3] by adding of a priori information and correction of the geomagnetic reference.
The MSA algorithm finds the correction vector for the D&I error terms and reference offset:
The solution Vslv is found by the differential evolution method [4] minimizing the following function:
Where f(Vslv) is the function of the total G, total B, and dip angle for the corrected surveys:
Gi and Bi are the gravity and magnetic measurement vector of the ith survey; AS and MS are the D&I scale factor matrixes; AB and MB are the D&I bias vectors.
The observation vector Vobs consists of the reference and a priori vectors:
The covariance matrix C is defined based on the observation vector:
Unlike the Novel MSA algorithm, the conventional MSA has the no-go zone [5]:
1. Bulychenkov, Konstantin. “Overcoming Fundamental Restrictions: Novel Multistation Measurement While Drilling Survey Correction.” SPE J. (2022;): doi: https://doi.org/10.2118/210084-PA
2. Brooks A. G., Gurden P. A., Noy K. A. 1998. Practical Application of a Multiple-Survey Magnetic Correction Algorithm. SPE 49060
3. Hanak F. C., Wilson H., Gjertsen M., 2015. Assessment of the Validity of MWD Survey Accuracy Following Multistation Analysis. SPE 173098
4. Storn, R.; Price, K., 1997, Differential evolution – a simple and efficient heuristic for global optimization over continuous spaces. Journal of Global Optimization. 11 (4): 341–359.
5. Nyrnes E., Torkildsen T., and Wilson H., 2009. Minimum requirements for multi-station analysis of MWD magnetic directional surveys. SPE/IDAC 125677