Structure of Turner Valley Gas and Oil Field, Alberta

Abstract

Turner Valley is structurally probably the most complicated oil field in North America. It is a highly folded and faulted compound anticlinal overthrust sheet bordering the outer Foothills Belt of Alberta. It involves Paleozoic limestones, dolomites, and shales, Jurassic shale, and Cretaceous rocks. From the surface, the structure appears to be rather simple, with apparently uninterrupted east and west rim rocks of Belly River sandstone enclosing Colorado shale. The major overthrust fault, which underlies part or all of the structure, is of considerable magnitude and appears to be warped. A high-gravity naphtha is produced with large volumes of gas from a dolomitized zone in the Paleozoic limestone, whereas small amounts of high-gravity crude are obtained from Mesozoic sa dstones at shallower depths. No connate water has been encountered in either the limestone or the upper producing sands. The heavier oils are found in the youngest formations and show a progressive decrease in gravity with depth. This paper consists of a discussion of the salient structural features, including two structure-contour maps, seven cross sections, an abridged geologic column, production statistics, and several photographs.