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Putnam, Peter E.1, Shawna Christensen1 
(1) Petrel Robertson Consulting Ltd, Calgary, AB

ABSTRACT: Geological Influences on Steam Chamber Growth within Steam-Assisted Gravity Drainage Reservoirs, Lower Cretaceous McMurray Formation, Northeastern Alberta, Canada

Several steam-assisted gravity drainage (SAGD) projects have recently been started or announced within McMurray Formation (Lower Cretaceous) fluvial-estuarine bitumen reservoirs located in northeastern Alberta. Over 700,000 bopd of new oil production could be derived from these projects. 
SAGD operates at sub-fracture pressures and McMurray Formation reservoirs are typically extremely heterogeneous; thus, the knowledge and prediction of the distribution of permeability obstructions is of fundamental importance. The influence of reservoir heterogeneities on steam chamber growth was assessed for two SAGD pilot projects; at the Devon-operated Dover Project and at Conoco-Phillips’ Surmont lease.

Significant geological findings include: 
1. Horizontal wells at Dover are perpendicular to dipping mudstone interbeds, whereas wells at Surmont parallel the main fluvial-estuarine axis. Well orientation appears to be an important influence on steam chamber growth and on the ability to drain oil from interbedded estuarine point bar successions. Although the bitumen column at Surmont is much thicker than that at Dover, oil productivity at Dover is better than at Surmont; 
2. Thin mud beds located between the injection and production wells may severely retard the development of a steam chamber; 
3. No mudstone interbed at either Dover or Surmont was observed to be one metre, or more, in thickness; the vast majority are 1-30 centimetres thick; below the resolution of most logging tools;
4. SAGD well productivity is a function of the growth of the steam chamber. It follows that the number and distribution of mudstone beds will greatly influence the economic success of SAGD projects.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.