Summary
EnCana Corporation’s Christina Lake Thermal Pilot Project located 170 km
south of Fort McMurray, Alberta, Canada, uses steam-assisted gravity drainage
(SAGD) technology to recover bitumen from the Lower Cretaceous McMurray
formation. This paper presents an analysis of time-lapse and crosswell seismic
data, as part of an overall study integrating different disciplines and
technologies, to understand the effects of geology on SAGD-process performance
in the pilot area.
A 3D baseline survey was conducted at the start of the pilot in 2001, and
two follow up surveys were conducted in 2004 and 2005. In addition, six
crosswell seismic profiles were acquired by placing both sources and receivers
in the vertical wellbores. The goal of the seismic surveys was to better
understand steam-chamber growth and reservoir architecture by detecting
lithology changes, including the occurrence and distribution of mudstone
stringers. Data from the surveys, especially from the crosswell profiles,
indicated significant reservoir heterogeneity, and helped to characterize
reservoir architecture in the pilot area more accurately.
Analysis of seismic data (both 4D and crosswell) showed steam-chamber growth
and oil recovery to be influenced strongly by reservoir geology. Steam-chamber
growth is especially affected by the presence of low-permeability facies in the
vicinity of the SAGD well pairs. Our analysis indicates that these reservoir
heterogeneities have contributed to the creation of areas within the reservoir
that have been unaffected by steaming operations to date. These findings are in
agreement with flow-simulation results and collectively contribute
significantly to the planning of future developments.
Introduction
The SAGD process was developed conceptually and investigated experimentally
by Butler (1994). Main features of the original SAGD model for the lateral
spread of the steam chamber included thermal conduction ahead of a
steady-moving steam-chamber interface; countercurrent gravity drainage of
mobilized bitumen, or heavy oil; and vertical rise of the steam chamber. This
recovery process was field tested at the Underground Test Facility (UTF) near
Fort McMurray through a number of different phases of pilot operation (Edmunds
et al. 1989; Komery et al. 1993). Field applications of the SAGD process have
revealed several issues of considerable importance to the recovery performance,
including wellbore hydraulics, reservoir heterogeneity, effects of solution
gas, and production of solids (Edmunds and Gittins 1993; Ito and Suzuki 1999;
Suggett et al. 2000; Ito 1999; Edmunds 1999; Birrell 2003). This paper relates
initial efforts undertaken by the Christina Lake Project team to integrate
geology, geophysics (specifically, seismic technology), and reservoir
engineering to further the understanding of steam-chamber growth in the
McMurray reservoir for the Christina Lake SAGD project.
Phase 1 of the SAGD pilot was implemented in 2001 at Christina Lake with the
drilling and completion of three SAGD well pairs (A1, A2, and A3). Since then,
three additional well pairs have been added (A4 well pair in October 2003 and
A5 and A6 well pairs in August 2004). Fig. 1 illustrates the project area (TWP
76, R06 west of 4th Meridian), which now includes six SAGD well pairs along
with observation wells and disposal wells. The following discussion will be
limited to A1 through A4 well pairs, as production histories for the A5 and A6
well pairs are rather limited.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
25 August 2005
- Meeting paper published:
1 November 2005
- Revised manuscript received:
22 January 2007
- Manuscript approved:
2 February 2007
- Version of record:
20 October 2007
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