methods prescribed by the SEC, which require the use of an average price, calculated as the twelve-
month average of the first-day-of-the-month reference price as adjusted for location and quality
differentials, unless prices are defined by contractual arrangements, excluding escalations based upon
future conditions.
We and our independent petroleum engineers used technical and economic data including, but not
limited to, well logs, geologic maps, seismic data, well test data, production data, historical price and
cost information, and property ownership interests. Our reserves have been estimated using
deterministic methods. Standard engineering and geoscience methods were used, or a combination of
methods, including performance analysis, volumetric analysis, and analogy, that we and our
independent petroleum engineers considered to be appropriate and necessary to categorize and
estimate reserves in accordance with SEC definitions and regulations. A substantial portion of these
reserves are for undeveloped locations; such reserves are based on estimates of reserve volumes and
recovery efficiencies along with analogy to properties with similar geologic and reservoir
characteristics. As in all aspects of oil and gas evaluation, there are uncertainties inherent in the
interpretation of engineering and geoscience data; therefore, our conclusions necessarily represent
only informed professional judgment.
As of December 31,
2011
2010
2009
Oil and Gas Proved Reserves
Consolidated entities
Oil (MBbls)
Proved developed . . . . . . . . . . . . . . . .
151,480
150,492
144,839
Proved undeveloped . . . . . . . . . . . . . .
92,550
72,776
69,191
244,030
223,268
214,030
Gas (MMcf)
Proved developed . . . . . . . . . . . . . . . .
454,248
517,183
509,121
Proved undeveloped . . . . . . . . . . . . . .
547,063
639,887
363,987
1,001,311
1,157,070
873,108
MBOE . . . . . . . . . . . . . . . . . . . . . . . . . . . .
410,915
416,113
359,548
Entity’s share of equity investee
(1)
Oil (MBbls)
Proved developed . . . . . . . . . . . . . . . .
4,921
4,315
Proved undeveloped . . . . . . . . . . . . . .
542
401
5,463
4,716
Gas (MMcf)
Proved developed . . . . . . . . . . . . . . . .
39,066
46,974
Proved undeveloped . . . . . . . . . . . . . .
8,982
15,394
48,048
62,368
MBOE . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13,471
15,111
Table continued on following page.
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