Reserves

Penn West for many years has annually submitted 100 percent of its reserve base to independent, third-party evaluation. GLJ Petroleum Consultants Ltd. evaluated Penn West's reserves for all properties and Sproule Associates Limited evaluated Canetic's, Titan's and Vault's reserves for all properties. The reserve estimates have been calculated in compliance with the National Instrument 51-101 Standards of Disclosure for Oil and Gas Activities ("NI 51-101"). Under NI 51-101, proved reserve estimates are defined as having a high degree of certainty with a targeted 90 percent probability that actual reserves recovered over time will equal or exceed proved reserve estimates. For proved plus probable reserves under NI 51-101, the targeted probability is an equal (50 percent) likelihood that the actual reserves to be recovered will be less than or greater than the proved plus probable reserves estimate.

Working Interest Reserves

Reserves
Estimates Category(1)(2)
Light and
Medium Oil
(mmbbls)
Heavy Oil
(mmbbls)
Natural Gas
(bcf)
Natural Gas
Liquids
(mmbbls)
boe(3)
(mmboe)
Proved                  
  Developed producing 151.4 41.9 621.1 15.2 312.0
  Developed non-producing 4.5 2.6 43.4 1.0 15.2
  Undeveloped 34.5 1.0 38.5 1.1 43.1
Total Proved 190.4   45.5   703.0   17.3   370.3
Probable 57.2 16.4 197.8 5.1 111.7
Total proved plus probable 247.6 61.9 900.8 22.4 482.0

(1) Working interest reserves before royalty burdens and excluding interests.
(2) Columns may not add due to rounding.

(3) boe @ 6:1

Pro forma(1) Penn West Working Interest Reserves

Reserves
Estimates Category(2)(3)
Light and
Medium Oil
(mmbbls)
Heavy Oil
(mmbbls)
Natural Gas
(bcf)
Natural Gas
Liquids
(mmbbls)
boe(4)
(mmboe)
Proved                  
  Developed producing 233.5 56.1 1,027.2 27.1 487.9
  Developed non-producing 5.3 3.0 66.3 1.4 20.8
  Undeveloped 38.7 1.5 62.2 1.4 52.0
Total Proved 277.5   60.6   1,155.7   29.9   560.6
Probable 89.7 20.6 414.6 10.2 189.7
Total proved plus probable 367.2 81.2 1,570.3 40.1 750.2

(1) Pro forma data includes Penn West, Canetic/Titan and Vault

(2) Working interest reserves before royalty burdens and excluding interests.
(3) Columns may not add due to rounding.

(4) boe @ 6:1