Open File Report 2013-17

Open File Report 2013-17

OFR 2013-17

Subsurface stratigraphic picks for the Milk River shoulder, Alberta Plains: including tops for the Milk River Formation and Alderson Member of the Lea Park Formation

Author(s) Glombick, P.M. Mumpy, A.J. Date 2014-05-08

This report provides the documentation to accompany a Digital Dataset of subsurface stratigraphic picks of the Milk River 'shoulder' in the Alberta Plains (Townships 1 to 73, Ranges 1W4 to 2W6) made from wireline geophysical well logs.

The Milk River 'shoulder' is an informal term often used to refer to a distinctive deflection on resistivity, sonic, density, and porosity logs. The Milk River 'shoulder' corresponds to the top of the Milk River Formation in southern Alberta, where it represents a juxtaposition of paralic deposits of the underlying Deadhorse Coulee Member of the Milk River Formation and overlying marine shale of the Pakowki Formation. It is characterized by a leftward deflection (decreasing resistivity) upwards across the contact, forming the distinctive log signature. To the north, the Milk River 'shoulder' represents the boundary between the Alderson Member (lower Lea Park Formation) and the upper Lea Park Formation (Pakowki equivalent). In these areas, silty sands and mudstones of the Alderson Member are overlain by shales of the upper Lea Park Formation.

Well data were screened to detect errors resulting from deviated wells, as well as incorrect ground and kelly bushing elevation data. We used statistical methods to identify local and regional statistical outliers, which we examined individually.