A study of stratigraphy and sedimentation in the formation of a stratigraphic trap, e.g. the Bellshill lake oilfield area of Alberta, Canada

Abstract

Stratigraphic traps are, in general, directly related to their respective depositional environments. An understanding of the depositional environment is essential to successful prospecting for oil and natural gas in this type of hydrocarbon reservoir. The concept of differential compaction of a sedimentary sequence makes isopach studies of shales immediately above (and below) a lenticular sand body or a knobbed blanket sand, of considerable value in isolating areas of interest to the Petroleum Geologist. The variations in thickness of these shales are independent of present day structure and these studies of such genetic sequences serve as real indicators of sand bodies and their depositional trend. Structure contour maps drawn on a reliable time marker (e.g. a marine transgression) within the selected genetic sequence can provide the information required to select a drilling location. In all such studies all the tools and data available to the Petroleum Geologist should be consulted and considered. This thesis is a brief account of the work of the Petroleum Geologist in the active search of oil and natural gas, the tools he uses, the data he consults, the regional depositional environment he must understand and a description of a typical example, the Bellshill Lake Oilfield, of one of the projects he is likely to be called upon to undertake.