Carbonate Reef Interpretation
Carbonate reef exploration is extremely important in the Canadian oil industry, with about 60% of petroleum production coming from Devonian reefs. In fact, the advent of modern Canadian oil production originated with the 1947 discovery of the Leduc #1 well. The Leduc discovery marked Alberta's economic advance as Canada's most prosperous province.
It is difficult to imagine that the ancient Devonian climate in Alberta was tropical and that today's oil deposits are largely the result of coral growth in balmy seas. In many ways, carbonate exploration requires that we turn back the geologic clock to reconstruct the setting for the creation of carbonate rocks as traps for oil and gas, because coral reefs require certain conditions of water depth and temperature. It will be our task to image carbonate reefs with seismic exploration tools. A good overview of seismic interpretation of reefs in Canadian exploration is given by Kuhme (1987).
Carbonate reefs generally are considered to be stratigraphic traps, with trapping mechanisms resulting from changes in lithology in a sedimentary environment.
In carbonate exploration, seismic methods usually do not involve imaging of steeply dipping beds. However, advanced migration methods are useful for collapsing seismic diffractions at the edge of the reef.
The analysis of carbonate reefs requires knowledge of the ancient shoreline, as shown in Figure 1. Sedimentary basins usually exist in deeper waters away from the shoreline, creating an environment for offshore shale deposition.
Shallow inland waters on the continental shelf are protected by a
Figures & Tables
Fundamentals of Geophysical Interpretation, SEG Geophysical Monograph Series No. 13, is a practical handbook for the petroleum geophysicist. Fundamental concepts are explained using heuristic descriptions of seismic modeling, deconvolution, depth migration, and tomography. Pitfalls in processing and contouring are described briefly. Applications include petroleum exploration of carbonate reefs, salt intrusions, and overthrust faults. The book includes past, present, and possible future developments in time-lapse seismology, borehole geophysics, multicomponent seismology, and integrated reservoir characterization.