NEW DATA AND INTERPRETATIONS FOR THE CARSON BASIN AND EASTERN GRAND BANKS

A Grand Banks well data sheet has been developed at the Geological Survey of Canada Atlantic for this relatively sparsely tested region. Existing and new data were integrated into a product that shows at a glance the current state of geoscience knowledge for a well. The complete suite of ten wells includes revised biostratigraphic analyses of rock samples that shows a substantial refinement in the ages of stratigraphic intervals and their environment of deposition. They are shown as columns tied to logs, lithology, previous biostratigraphic data and formation boundaries, which are in turn linked to seismic data. The synthetic seismogram from the well data shows the interpretation of the main lithostratigraphic markers and the seismic expression at the well location. This is somewhat problematic with the vintage seismic available from the pre 3D/GPS seismic era; the method for the interpretation is shown. The second part of each well sheet shows a combined pressure/temperature/petrophysics/maturity diagram that indicates whether the well encountered overpressure as based on mud weights; what the Horner plot corrected temperatures are and the corresponding lithology with formation tops. The log data have been used to indicate where the onset of overpressure starts, whether the mud weights indicated overpressure correctly, and where there are indications of released overpressure. Thermal maturity for hydrocarbon generation is shown from new and old Rock Eval Tmax and vitrinite data. These measurements may be suppressed by overpressure, which lowers the level of the oil window and has important consequences for basin modeling of the petroleum system. Conversely, overpressure appears to be caused at least in part by hydrocarbon generation, which adds a further complication to making a predictive model as a final synthesis of this effort. A text block succinctly explains the results and the surmised rationale for drilling the well. Overall, these sheets present a concise overview of the results from studies over the past 25 years and will be important guides for the next phase of future exploration activity.