Sedimentological and sequence stratigraphic model of the Falher "D" Pool, Lower Cretaceous, northwestern Alberta

Sequence stratigraphy has been increasingly used as a correlation technique by both academic and petroleum geologists. This approach puts primary emphasis upon the surfaces that bound genetically related stratigraphic successions. In this study of the Falher "D" Pool, the use of a sequence stratigraphic approach helps identify four depositional intervals within the Falher "D" interval; these are termed D1, D2, LS1 and D3. Conglomeratic strata, abundant only in the D2 interval, represent the principal gas-producing lithofacies in the "D" Pool. Deposition of gravelly sediment along the D2 shoreline was terminated by a relative sea level fall that shifted the local shoreline northward and created a sequence boundary. The sharp northern boundary of the "D" Pool is attributed to this event. Subsequently, following the reestablishment of stillstand progradation, the nearshore strata of LS1 were deposited above the sequence boundary. Progradation during this episode caused the shoreline to migrate beyond the northern limit of the study area. Nevertheless, at some later time, but still during Falher "D" time, the shoreline returned into the study area. Despite the deposition of a thick nearshore succession, strata of D3 consist only of nonreservoir sandstones. This suggests that not only were changes of relative sea level important in controlling the distribution of reservoir strata within the study area but, also, temporal changes in the nature of sediment being supplied to the Falher shoreline - namely the relative proportion of gravel to finer-grained sediments.