Summary
Horizontal wells are widely drilled to produce heavy oil because of their
large reservoir contact. For example, there are more than 500 horizontal wells
operated in cyclic-steam-stimulation (CSS) or steam-assisted gravity-drainage
(SAGD) processes in Liaohe oil field. The length of these horizontal wells
usually ranges from 100 to 500 m. But it is challenging to recover oil along a
horizontal well proportionally by conventional steam-injection processes
because of poor steam conformance along the horizontal well, which is derived
from reservoir heterogeneity, large horizontal-well length, and steam
properties. Field investigation shows that only half of the reservoir along the
horizontal well is well steamed and recovered, and that the average ratio of
oil production to steam injection (OSR) is less than 0.28. In this paper, a
separated-zones steam-injection process is introduced to improve steam
conformance along the horizontal well; in this process, in which packers,
outlets, pressure-sensitive valves, and ball sealers are involved, steam could
be injected to the selected zone, separated dual zones in sequence or at one
time, or separated multizones simultaneously. In order to investigate steam
conformance along the horizontal well and feasibility of separated-zones steam
injection, primary laboratory experiments with a sand-packaged model, numerical
simulation, and field testing are carried out. These show that steam injected
to separated zones could be regulated with sealed packer(s) based on the
principles of steam crossflow and superimposing the effect near the packer;
therefore, steam conformance along the horizontal well could be considerably
improved by separated-zones steam injection. Field testing of 76 wells
stimulated by separated-zones steam injection shows that up to 70% of the
reservoir along the horizontal well is well steamed on average, and steam
conformance is significantly improved.
© 2012. Society of Petroleum Engineers
View full textPDF
(
2,471 KB
)
History
- Original manuscript received:
6 February 2011
- Meeting paper published:
19 October 2010
- Revised manuscript received:
15 August 2011
- Manuscript approved:
3 November 2011
- Published online:
9 March 2012
- Version of record:
14 March 2012
View Cart
