ABSTRACT

The Rycroft Halfway C Pool is located approximately 400 km northwest of Edmonton. The pool currently produces 466 m³/d of 38° API oil from 20 wells and contains 4.4 10⁶m³ OOIP. The waterflood secondary recovery scheme currently in place is expected to recover 37 per cent of the OOIP. The pool was discovered in 1984 and waterflooding commenced in 1987.

The geological history of the area is very complex. Facies variations associated with minor faulting have created 10 individual hydrocarbon productive reservoirs within the Rycroft Halfway C Pool. The Halfway was subdivided into two units, a lower Stacked Bar Sequence (SBS) and an upper Tidal Flat Sequence (TFS). Depositional environment of the TFS ranges from nearshore marine/intertidal to supratidal/coastal sabkha. The productive facies range from very fine grained dolomitic sandstone to finely crystalline dolomitized algal mats. Depositional environment of the SBS was a prograding beach/barrier island system. The productive facies display gradations from very fine grained dolomitic sandstone to sandy, very finely crystalline dolomite (coquina).

In order to optimize pool development and to design an effective secondary recovery scheme, all potentially productive hydrocarbon reservoirs had to be evaluated thoroughly. Detailed core examination, core analysis (including petrography), and well log evaluation provided the key to creating the geological model.

This case history illustrates that recognition of depositional environments and the subsequent detailed geological evaluation of a complex reservoir are essential to the delineation of the pool and the design of an effective secondary recovery scheme.

End_of_Record - Last_Page 225-------