Annual report pursuant to Section 13 and 15(d)

Note 20 - Supplemental Oil and Gas Disclosures - Estimated Quantities of Net Proved, Proved Developed and Proved Undeveloped Oil, NGLs and Natural Gas Reserves (Details)

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Note 20 - Supplemental Oil and Gas Disclosures - Estimated Quantities of Net Proved, Proved Developed and Proved Undeveloped Oil, NGLs and Natural Gas Reserves (Details)
ft³ in Billions, Boe in Billions
 12 Months Ended
Dec. 31, 2019
MMBoe
Mcfe
ft³
MMBbls
Dec. 31, 2018
Boe
MMBoe
Mcfe
ft³
MMBbls
Dec. 31, 2017
Boe
MMBoe
Mcfe
ft³
MMBbls
Oil [Member]      
Proved reserves, balance (Million Barrels of Oil) 39.1 34.4 32.9
Revisions of previous estimates (Million Barrels of Oil) 1.4 [1] 11.6 [2] 4.5 [3]
Extensions and discoveries (Million Barrels of Oil) 0.9 [4] 0.5 [5] 4.1 [6]
Production (Million Barrels of Oil) (6.7) (6.7) (7,100,000)
Purchase of minerals in place (Million Barrels of Oil) 3,100,000 [7] 1.5 [8]  
Sales of minerals in place (Million Barrels of Oil) [9]   (2.2)  
Proved reserves, balance (Million Barrels of Oil) 37.8 39.1 34.4
Proved reserves, ending balance (Million Barrels of Oil) 28 31.5 26.1
Undeveloped reserves, ending balance (Million Barrels of Oil) 9.8 [10] 7.6 8.3
Natural Gas Liquids [Member]      
Proved reserves, balance (Million Barrels of Oil) 9.8 7.8 8.2
Revisions of previous estimates (Million Barrels of Oil) (1.5) [1] 2.8 [2] 0.7 [3]
Extensions and discoveries (Million Barrels of Oil) 0.1 [4] 0.3 [5] 0.3 [6]
Production (Million Barrels of Oil) (1.3) (1.3) (1.4)
Purchase of minerals in place (Million Barrels of Oil) 17.4 [7] 0.4 [8]  
Sales of minerals in place (Million Barrels of Oil) [9]   (0.2)  
Proved reserves, balance (Million Barrels of Oil) 24.5 9.8 7.8
Proved reserves, ending balance (Million Barrels of Oil) 21.7 7.8 7.2
Undeveloped reserves, ending balance (Million Barrels of Oil) 2.8 [10] 2 0.6
Natural Gas [Member]      
Proved reserves, balance (Million Barrels of Oil) | ft³ 210.5 192.2 197.8
Revisions of previous estimates (Million Barrels of Oil) | ft³ (16.9) [1] 40.4 [2] 25.8 [3]
Extensions and discoveries (Million Barrels of Oil) | ft³ 1.2 [4] 7.7 [5] 5.4 [6]
Production (Million Barrels of Oil) | ft³ (41.3) (32.0) (36.8)
Purchase of minerals in place (Million Barrels of Oil) | ft³ 417.6 [7] 9.4 [8]  
Sales of minerals in place (Million Barrels of Oil) | ft³ [9]   (7.2)  
Proved reserves, balance (Million Barrels of Oil) | ft³ 571.1 210.5 192.2
Proved reserves, ending balance (Million Barrels of Oil) | ft³ 504.9 166.8 173.5
Undeveloped reserves, ending balance (Million Barrels of Oil) | ft³ 66.2 [10] 43.7 18.7
Oil Equivalent [Member]      
Proved reserves, balance (Millions of Barrels of Oil Equivalent) | MMBoe [11] 84 74.2 74
Revisions of previous estimates (Millions of Barrels of Oil Equivalent) | MMBoe [11] (3) [1] 21.1 [2] 9.6 [3]
Extensions and discoveries (Millions of Barrels of Oil Equivalent) | MMBoe 1.1 [4] 2.1 [5],[11] 5.2 [6],[11]
Production (Millions of Barrels of Oil Equivalent) | MMBoe [11] (14.8) (13.3) (14.6)
Purchase of minerals in place (Millions of Barrels of Oil Equivalent) | MMBoe 90.1 [7] 3.4 [8],[11]  
Sales of minerals in place (Millions of Barrels of Oil Equivalent) | MMBoe [9],[11]   (3.5)  
Proved reserves, balance (Millions of Barrels of Oil Equivalent) | MMBoe [11] 157.4 84 74.2
Proved reserves, ending balance (Millions of Barrels of Oil Equivalent) | MMBoe 133.8 67 [11] 62.2 [11]
Undeveloped reserves, ending balance (Millions of Barrels of Oil Equivalent) | MMBoe 23.6 [10] 17 [11] 12 [11]
Natural Gas Equivalent [Member]      
Proved reserves, balance (Millions of Barrels of Oil Equivalent) [11] 504,100,000 445.3 444,000,000
Revisions of previous estimates (Millions of Barrels of Oil Equivalent) | Mcfe [11] (18,200,000) [1] 126,700,000 [2] 57,400,000 [3]
Extensions and discoveries (Millions of Barrels of Oil Equivalent) | Mcfe 6.7 [4] 12,600,000 [5],[11] 31,300,000 [6],[11]
Production (Millions of Barrels of Oil Equivalent) [11] (89,000,000) (80,000,000) (87.4)
Purchase of minerals in place (Millions of Barrels of Oil Equivalent) | Mcfe 540,900,000 [7] 20,700,000 [8],[11]  
Sales of minerals in place (Millions of Barrels of Oil Equivalent) | Mcfe [9],[11]   (21,200,000)  
Proved reserves, balance (Millions of Barrels of Oil Equivalent) [11] 944,500,000 504,100,000 445.3
Proved reserves, ending balance (Millions of Barrels of Oil Equivalent) | Mcfe 802,900,000 402,200,000 [11] 373,300,000 [11]
Undeveloped reserves, ending balance (Millions of Barrels of Oil Equivalent) | Mcfe 141,600,000 [10] 101,900,000 [11] 72,000,000 [11]
[1] Primarily related to upward revisions related to our Ship Shoal 028 field and our Main Pass 108 field. Additionally, decreases of 10.0 MMBoe were due to price revisions for all proved reserves, which includes estimated price revisions of the purchase of minerals in place from the date of purchase to December 31, 2019.
[2] Primarily related to upward revisions at our Mahogany field and our Ship Shoal 028 field. Additionally, increases of 2.3 MMBoe were due to price revisions.
[3] Primarily related to upward revisions at our Mississippi Canyon 698 (Big Bend) field, our Fairway field, our Ewing Bank 910 field and our Viosca Knoll 783 (Tahoe/SE Tahoe) field. Additionally, increases of 3.4 MMBoe were due to price revisions.
[4] Primarily related to extensions and discoveries of 0.9 MMBoe at our Mississippi Canyon 800 (Gladden) field.
[5] Primarily related to extensions and discoveries of 1.3 MMBoe at our Viosca Knoll 823 (Virgo) field and 0.7 MMBoe at our Ewing Bank 910 field.
[6] Primarily related to extensions and discoveries at our Ship Shoal 349 (Mahogany) field of 3.5 MMBoe and at our Main Pass 286 field of 1.5 MMBoe.
[7] Primarily related to the Mobile Bay Properties and Magnolia acquisitions
[8] Primarily related to our Ship Shoal 028 field and our Green Canyon 859 field (Heidelberg).
[9] Primarily related to conveyance of interest in properties related to the JV Drilling Program.
[10] We believe that we will be able to develop all but 2.5 MMBoe (approximately 11%) of the total of 23.6 MMBoe reserves classified as proved undeveloped ("PUDs") at December 31, 2019, within five years from the date such reserves were initially recorded. The lone exceptions are at the Mississippi Canyon 243 field (Matterhorn) and Virgo deepwater fields where future development drilling has been planned as sidetracks of existing wellbores due to conductor slot limitations and rig availability. Three sidetrack PUD locations, two at Mississippi Canyon 243 (Matterhorn) field and one at Virgo, will be delayed until an existing well is depleted and available to sidetrack. Based on the latest reserve report, these PUD locations are expected to be developed in 2021 and 2022, respectively.
[11] The conversion to barrels of oil equivalent and cubic feet equivalent were determined using the energy-equivalent ratio of six Mcf of natural gas to one barrel of crude oil, condensate or NGLs (totals may not compute due to rounding). The energy-equivalent ratio does not assume price equivalency, and the energy-equivalent prices for crude oil, NGLs and natural gas may differ significantly.