Impairment Charges (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Impairment Loss Recognised Or Reversed [Abstract]

Summary of Forward Prices Used to Determine Future Cash Flows

The forward prices as at June 30, 2018, used to determine future cash flows from crude oil, NGLs and natural gas reserves were:

	Remainder       of 2018		2019		2020		2021		2022		Average Annual Increase Thereafter
WTI (US$/barrel) (1)		68.42		65.77		67.87		69.67		72.35		2.1	%
WCS (C$/barrel) (2)		59.66		61.15		64.41		66.51		68.22		2.1	%
Edmonton C5+ (C$/barrel)		88.18		81.66		82.01		83.30		85.15		2.1	%
AECO (C$/Mcf) (3) (4)		1.90		2.37		2.83		3.13		3.36		2.0	%

(1) West Texas Intermediate (“WTI”).

(2) Western Canadian Select (“WCS”).

(3) Alberta Energy Company (“AECO”) natural gas.

(4) Assumes gas heating value of one million British thermal units (“MMBtu”) per thousand cubic feet.

Summary of Increase (Decrease) to Impairment

As at June 30, 2018, a change in the discount rate or forward commodity prices would have had the following impact on the impairment of the Clearwater CGU:

	Increase (Decrease) to Impairment
	One Percent Increase in the Discount Rate		One Percent Decrease in the Discount Rate			Five Percent Increase in the Forward Price Estimates			Five Percent Decrease in the Forward Price Estimates
Clearwater		24		(26	)		(54	)		59