Overview of a Steam-Assisted Gravity
Drainage (SAGD) Reservoir
Characterization Strategy for Horizontal Well Placement and Ranking Within the
Surmont Lease, McMurray Oil Sands, Alberta
David Garner1, Thomas J. Wheeler1, Emmanuel
Mus2, and Jean-François Richy2
1 ConocoPhillips Canada,
Calgary, AB
2 Total, seconded to ConocoPhillips
Canada, Calgary, Canada,
The McMurray formation is a highly heterogeneous Cretaceous clastic
reservoir with thick, bitumen-saturated sands. We applied a detailed
quantitative workflow for integrating multi-scale data
, building a geological
model and managing uncertainties associated with planning and controlling a
steam chamber for SAGD bitumen extraction. Our main goals in this study were to
aid and improve the complex decision making for vertical placement of horizontal
wells, for optimizing expected performance, and for ranking of the horizontal
well pairs.
Let us consider that the SAGD wells can be studied as individual reservoirs, with a drainage volume surrounding each well pair. There is a line of sight (LOS) along the length of the horizontal path or vertical plane, and a width. Using the drainage volume and LOS we calculated parameters such as effective well length, net-to-gross, facies proportions, producible volumes, and a vertical discount factor on stranded volumes for each model realization. A comparison was made to the purely deterministic geological approach.
The evaluation focused on the uncertainties in the estimated or simulated
reservoir parameters. To decide on placement, post-processing
of the detailed
geostatistical simulations provided uncertainty measures on the reservoir
parameters as a function of elevation. A probabilistic model was used to
simulate well pair performance and rank the well slots. The model used well
placements, extracted reservoir parameter distributions, SAGD operating
conditions, and Butler theory in a Monte Carlo framework.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005