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Reserves

OPTI has a 50 percent working interest in three oil sands properties in the Athabasca oil sands area, with Nexen owning the other 50 percent: Long Lake, Leismer and Cottonwood.

The McDaniel & Associates Consultants Ltd. (McDaniel) evaluation of our Long Lake Phase 1 and 2 lands recognizes the impact of upgrading on the resources. Most of the raw bitumen will be upgraded and sold as Premium Sweet Crude (PSC^TM) and butane, and is shown as synthetic crude oil or butane reserves. Bitumen will be sold upon start-up of steam assisted gravity drainage (SAGD) operations prior to Upgrader start-up, and thereafter during periods of Upgrader downtime, and is shown as bitumen reserves. The following table shows OPTI’s working interest in the raw bitumen reserves and the corresponding sales volumes.

All volumes are millions of barrels. 

	Gross Sales Volumes
2007
	Raw Bitumen	Bitumen	PSCTM	Butane
Proven	268	16	202	3
Proven plus Probable	803	29	620	9
Proven plus Probable plus Possible (1)	941	29	731	10
The corresponding reserve estimates at December 31, 2006 were as follows:
2006
Proven plus Probable plus Possible	587	23	452	6

Note: (1)  Possible reserves are those additional reserves that are less certain to be recovered that probable reserves. There is a 10 percent probability that the remaining quantities actually recovered will be greater than the sum of proved plus probable plus possible reserves.


McDaniel has prepared a report evaluating the bitumen reserves and synthetic oil reserves of the Long Lake leases effective as of December 31, 2007.  Due to the advanced nature of Long Lake Phase 2, previously recognized contingent resources are now booked as probable and possible reserves. The reporting of reserves meets the requirements of National Instrument 51-101 issued by the Canadian Securities Administration.

Resources

OPTI and Nexen have conducted delineation activities on their jointly owned leases. Utilizing the results of these activities, estimates of recoverable bitumen resources on the leases have been prepared. In addition to estimating our reserves, McDaniel has estimated bitumen resources on all of OPTI's lands, including the Long Lake, the Leismer and the Cottonwood leases.  A summary of the additional resource estimates on a net basis to us is shown below. These estimates represent initial recoverable resource estimates and are not classified or recognized as reserves.

All volumes are millions of barrels.

	Raw Bitumen (1)
	Best Estimate
Remainder of Long Lake Leases (2)	704
Leismer (2)	960
Cottonwood(3)	542
Total net to OPTI	2,206

Notes:  
(1) These estimates represent the "best estimate" of our resources, are not classified or recognized as reserves, and are in addition to our disclosed reserve volumes.  These resource estimates are categorized primarily as Contingent Resources, with some categorized as Prospective Resources.  See Notes 2 and 3 below.
Contingent Resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from known accumulations using established technology or technology under development, but which are not currently considered to be commercially recoverable due to one or more contingencies. Contingencies may include factors such as economic, legal, environmental, political, and regulatory matters, or a lack of markets. It is also appropriate to classify as Contingent Resources the estimated discovered recoverable quantities associated with a project in the early evaluation stage.  There is no certainty that it will be commercially viable to produce any portion of the Contingent Resources.Prospective Resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from undiscovered accumulations by application of future development projects. Prospective resources have both an associated chance of discovery and a chance of development. There is no certainty that any portion of the Prospective Resources will be discovered.  If discovered, there is no certainty that it will be commercially viable to produce any portion of the resources.
(2) The resource estimates for Leismer and Long Lake are categorized as Contingent Resources.  These volumes are classified as resources rather than reserves primarily due to less delineation and the absence of regulatory approvals, detailed design estimates and near-term development plans.
(3) The estimate for Cottonwood is categorized as both Contingent and Prospective Resources.  The estimate of 542 million barrels is comprised of 247 MMbbl of Contingent Resources and 295 MMbbl of Prospective Resources. These Contingent Resource volumes are classified as resources rather than reserves primarily due to less delineation; the absence of regulatory approvals, detailed design estimates and near-term development plans; and less certainty of the economic viability of their recovery.  In addition to those factors that result in Contingent Resources being classified as such, Prospective Resources are classified as such due to the absence of proximate delineation drilling.