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OWSG Survey Tool Error Models
This page is for the OWSG Survey Tool Error Models and will be updated with information as it is generated - Please check back regularly.

OWSG Positional Uncertainty Models


The full set of ISCWSA compliant OWSG Positional Uncertainty (PU) models are now available for your use.


As with all error models, users must ensure that they are applicable and valid for use in their situations.


The A, B, C & D sets can be accessed in the excel format described at the ISCWSA #38 meeting in New Orleans. Some further materials are still being developed and will be accessible from the same web location as they become available.


Both ConocoPhillips and Chevron anticipate making use of these positional uncertainty models.


It is proposed that these survey tool error models will be published as an SPE paper in the future.


While these models have been branded as OWSG, a sub-committee of the ISCWSA, the models are simply offered as one possible set of models that are compliant with the ISCWSA PU modelling and are neither endorsed not approved by the ISCWSA. The OWSG aims to improve common practice and offers these as a potential way of improving consistency. The A and B sets are generic models and may be replaced by a specific model offered by a survey tool contractor (C set). Good practice is to pair use of a model with a corresponding QA/QC. While the C set has been checked for consistency with the ISCWSA model framework the parameter term values are set by the survey tool provider


Please note that the only ISCWSA endorsed and approved PU model are MWD, MWD + Axial, MWD + Sag, MWD + Axial + Sag for surveys taken from a fixed installation and for surveys taken from a floating installation, i.e. there are eight PU models in total. These are available from the ISCWSA model maintenance sub-committee documented on



OWSG Standard Set A (Revision 5 - 12-Oct-2017 with Extended Course Length Term - Under Review)


Set A is a minimum set of general Survey Tool Error Models that will cover most survey scenarios. It contains 30 models and covers the most common magnetic survey tools. There are three Generic North Seeking Gyro models, camera based film survey tools for legacy surveys, as well as Inclination-Only models for actual inclination data and well planning. A list of Set A Survey Tool Models is included in Appendix A.


Like the original ISCWSA tool error models, the magnetic models are based the BGGM geomagnetic model and assume the tool is properly functioning and the QA/QC checks have passed.


To keep the Set to a manageable size, not all the possible combinations of survey corrections have been included, but have been restricted to the most common. The corrections include valid combinations of IFR1, IFR2, Axial Drillstring Magnetic Interference Correction, Multi-Station Correction and BHA Sag Correction.


OWSG Set A Index and Survey Tool Error Models in Microsoft Excel format (Opens New Window)


OWSG Extended Set B (Revision 5 - 12-Oct-2017 with Extended Course Length Term - Under Review)


Set B contains 22 additional survey tool error models to supplement the Standard Set A. They cover the use of different geomagnetic models (HDGM, IGRF, and WMM) and less used survey tools or techniques.


OWSG Set B Index and Survey Tool Error Models in Microsoft Excel format (Opens New Window)



OWSG Contractor Set C


These models are provided by the survey contractors. The formats will be checked to ensure that they comply with the OWSG format and that there are no obvious errors. However the actual terms and values will remain the responsibility of the supplier.


Contractor models may be used where the survey tool is applicable to the specific model and the relevant QA/QC checks for the tool have been made.


Note: This Set is a work in progress and is not a complete list.


OWSG Set C Index and Survey Tool Error Models in Microsoft Excel format - Coming Soon




OWSG Template Set D


This set currently contains templates for the six ISCWSA Gyro Model Tools as published in SPE 90408.


Note: These are error model template files and should not be used without modifying the term values, which were only issued to allow testing of the tool model implementation.


There are no magnetic survey tool templates as the Standard MWD in Set A can be used as a magnetic model template.


OWSG Set D Index and Survey Tool Error Models in Microsoft Excel format (Opens New Window)




OWSG Other Set E (Revision 5 - 12-Oct-2017 with Extended Course Length Term - Under Review)


This set is to ensure that the Standard and Extended Sets (A and B) are kept ‘clean’ by providing a Set for customised, experimental or operator specific Survey Tool Error Models.


OWSG Set E Index and Survey Tool Error Models in Microsoft Excel format (Opens New Window)