Mapping Formation-Top Offsets in the Southwestern Alberta Plains, Canada: Methodology and Results

Publication Type
Open File Report
Topic
Oil and Gas
Publication ID
OFR 2020-02
Publication ID Extended
Open File Report 2020-02
Publication
Abstract

This report presents the results of subsurface bedrock structure mapping in southwestern Alberta, Canada, using a methodology that assesses formation-top offsets. Three stratigraphic horizons were selected for mapping subsurface bedrock offsets: the base of the Fish Scales Formation, the top of the Milk River Formation, and the lower Bearpaw Formation flooding surface. The selected surfaces represent, or are close to, marine flooding surfaces in this area and can be considered to approximate a flat-lying surface (datum) and, therefore, are ideal for mapping post-depositional structures. A bedrock offset is defined in this report as any lineament or possible vertical displacement of a bedrock horizon that has been detected using geostatistical analysis of well-log data. This methodology identified numerous potential offsets which have been highlighted using residual maps of these three surfaces. The offset features identified from these surfaces were compared to each other, and to an isopach map of the interval from the base of the Fish Scales Formation to the top of Milk River Formation to evaluate whether these offsets represent potential growth faults. Some of the offsets mapped in this report were found to coincide with previously reported faults, which were identified at isolated riverbank outcrops and interpreted from seismic reflection surveys, and allow for determination of fault orientation and extent. The other offsets highlighted in this report may represent potential faults or differential compaction and highlight areas of geological interest for future structural analysis.

Citation

Mei, S and R. Schultz (2020): Mapping formation-top offsets in the southwestern Alberta Plains, Canada: methodology and results; Alberta Energy Regulator / Alberta Geological Survey, AER/AGS Open File Report 2020-02, 34 p.

Place Keywords
alberta, canada, southwest alberta
Place Keywords NTS
72e, 72l, 82h, 82i
Theme Keywords
bearpaw formation, cretaceous, fault, fish scales formation, geology, geostatistics, milk river formation, stratigraphic picks, structural geology, subsurface mapping