Abstract
Several partially scaled laboratory model experiments were conducted to
evaluate a hybrid solvent-steam process for recovery of heavy oil or bitumen.
All experiments used Athabasca UTF bitumen, and modelled a 30-metre-thick
formation. The experiments were compared using a common set of economic
assumptions. The experiments showed that a hybrid solvent-steam process could
recover bitumen at steam-oil ratios much lower than those observed for steam
assisted gravity drainage (SAGD), and achieve reasonable ultimate oil recovery
(60% IOIP). The economic analysis based on experiments indicated that a hybrid
solvent-steam process could be more cost-effective than SAGD for a 30-m
Athabasca formation.
Introduction
Some heavy oil reservoirs are difficult to produce by cold production. The
oil may be immobile at reservoir temperature, or there may be some initial oil
mobility and some reservoir drive energy, but the sand strength precludes the
production of wormholes. These reservoirs may contain dead oil, as in the case
of Athabasca bitumen, or they may have some dissolved gas, as in the case of
Cold Lake or Burnt Lake reservoirs.
SAGD is the main commercial technology used for in-situ recovery of these
oils. Because of the increasing costs for energy (natural gas) and the
increasing restrictions on fresh water usage, solvent-based processes (VAPEX,
Thermal Solvent, Hybrid Solvent, N-Solv, Savex) have been proposed as
alternative technologies for heavy oil and bitumen production. Most of these
technologies utilize a pair of horizontal wells, similar to those used in SAGD,
but use a gaseous solvent, typically propane, alone or in conjunction with
steam, to recover the oil.
The VAPEX process may be augmented by adding heat. Heating of a horizontal
wellbore will reduce bitumen viscosity sufficiently to produce a large increase
in oil production rate. The heat also serves to initiate communication between
the injector and the producer. The heat also serves to speed the diffusion of
solvent into the oil. The combination of heated wellbores and VAPEX is known as
the thermal solvent process.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
27 March 2008
- Meeting paper published:
17 June 2008
- Revised manuscript received:
29 September 2009
- Manuscript approved:
1 October 2009
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