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  • Writer's pictureRaid Attir

28 - Is Canada Oil Patch Giving Up on its 1965 UWI System?

Updated: Apr 12, 2019

Thousands of wells are being drilled in Canada every year (~7,000 wells in 2017, with a peak of ~25,000 wells in 2005). To keep track of all these wells, the Geoscience Data Committee of CAPP (Canadian Petroleum Association back then) developed in 1965 a 16-character Unique Well Identifier (UWI) system, which aimed to give a unique identity to each well in Canada.

In recent years, the UWI limitations started to surface. As more complex wells are drilled (e.g. Horizontal, ERD, Multilateral, dual completion), UWI showed inability to cope with these changes and became partially unreliable. This pushed a group of operators, provincial regulators, and data vendors in 2014 to develop a more robust system, which they called the Canadian Well Identification System (CWIS).

In 2015, Saskatchewan became the first jurisdiction to implement the CWIS


Brief History on Unique Well Identifier (UWI)

The UWI system identifies well events using a legal survey system that gives an approximate location of a well target. The UWI has 4 components:

  • Legal survey location which identifies the jurisdiction

  • Survey system code which gives the approximate target location

  • Location exception code which identifies the licensing sequence of wells within a legal subdivision

  • Event sequence code which indicates the chronological sequence of operations (or events) that yield a separate and unique set of geological or production data

The location component describes the bottom-hole location of the well, not the surface location


What are the Unique Well Indetifier (UWI) Limitations?

Some limitations of the UWI system:

  • It identifies an event rather than a well (or a parent well)

  • It does not distinguish between drilling and completion activities (in other words, between well construction and well intervention)

  • Requires a lengthy amendment process if target location isn't where planned

  • Might be misleading as surface location and bottom hole location might be in two different legal subdivisions

A Legal Subdivision is a the smallest area in the Dominion Land Survey (DLS) system used by the Prairie provinces. It measures 402 m x 402 m


What Is The Canadian Well Identification System (CWIS)?

The Canadian Well Identification System (CWIS) is published by the Professional Petroleum Data Management (PPDM) Association. It identifies wells using three related identifiers:

  • Well ID to identify all subsurface components sharing a unique well origin

  • Wellbore ID to idenfity a unique drilled path from the well origin to a terminating point

  • Well Reporting ID to identify the production from a unique completion string (including commingled production), as well as the injection of fluids back into the formation.

The CWIS solves the problem of well identity, uniqueness, and distinction between activities.


Final Words

The CWIS intends to replace the UWI. However, it doesn't put an end to it, as the UWI will have a continuing role in the end-user market. Therefore, It is up to the provincial regulator to elect when and how to adapt the CWIS, if they wish to do so.


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