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Oil and Gas Exploration and Production Industries Disclosures (Tables)
 12 Months Ended
Dec. 31, 2018
Oil and Gas Exploration and Production Industries Disclosures [Abstract]  
Net Proved and Proved Developed Oil and Gas Reserve Quantities
The following tables set forth EOG's net proved reserves at December 31 for each of the four years in the period ended December 31, 2018, and the changes in the net proved reserves for each of the three years in the period ended December 31, 2018, as estimated by the Engineering and Acquisitions Department of EOG:
NET PROVED RESERVE SUMMARY
 
United
States
 
Trinidad
 
Other
International (1)
 
Total
NET PROVED RESERVES
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Crude Oil (MBbl) (2)
 
 
 
 
 
 
 
Net proved reserves at December 31, 2015
1,087,860

 
1,069

 
8,667

 
1,097,596

Revisions of previous estimates
42,040

 
54

 
861

 
42,955

Purchases in place
25,795

 
—

 
—

 
25,795

Extensions, discoveries and other additions
123,441

 
—

 
—

 
123,441

Sales in place
(8,791
)
 
—

 
—

 
(8,791
)
Production
(101,854
)
 
(284
)
 
(1,273
)
 
(103,411
)
Net proved reserves at December 31, 2016
1,168,491

 
839

 
8,255

 
1,177,585

Revisions of previous estimates
57,935

 
80

 
(179
)
 
57,836

Purchases in place
1,111

 
—

 
—

 
1,111

Extensions, discoveries and other additions
207,137

 
301

 
119

 
207,557

Sales in place
(8,393
)
 
—

 
—

 
(8,393
)
Production
(122,210
)
 
(322
)
 
(191
)
 
(122,723
)
Net proved reserves at December 31, 2017
1,304,071

 
898

 
8,004

 
1,312,973

Revisions of previous estimates
(13,237
)
 
(183
)
 
44

 
(13,376
)
Purchases in place
2,743

 
—

 
—

 
2,743

Extensions, discoveries and other additions
383,003

 
—

 
15

 
383,018

Sales in place
(768
)
 
—

 
(6,310
)
 
(7,078
)
Production
(144,128
)
 
(298
)
 
(1,542
)
 
(145,968
)
Net proved reserves at December 31, 2018
1,531,684

 
417

 
211

 
1,532,312

 
 
 
 
 
 
 
 
Natural Gas Liquids (MBbl) (2)
 

 
 

 
 

 
 

Net proved reserves at December 31, 2015
382,875

 
—

 
—

 
382,875

Revisions of previous estimates
53,771

 
—

 
—

 
53,771

Purchases in place
1,284

 
—

 
—

 
1,284

Extensions, discoveries and other additions
41,862

 
—

 
—

 
41,862

Sales in place
(33,548
)
 
—

 
—

 
(33,548
)
Production
(29,878
)
 
—

 
—

 
(29,878
)
Net proved reserves at December 31, 2016
416,366

 
—

 
—

 
416,366

Revisions of previous estimates
46,843

 
—

 
—

 
46,843

Purchases in place
421

 
—

 
—

 
421

Extensions, discoveries and other additions
75,003

 
—

 
—

 
75,003

Sales in place
(2,887
)
 
—

 
—

 
(2,887
)
Production
(32,273
)
 
—

 
—

 
(32,273
)
Net proved reserves at December 31, 2017
503,473

 
—

 
—

 
503,473

Revisions of previous estimates
23,942

 
—

 
—

 
23,942

Purchases in place
2,006

 
—

 
—

 
2,006

Extensions, discoveries and other additions
127,409

 
—

 
—

 
127,409

Sales in place
(41
)
 
—

 
—

 
(41
)
Production
(42,460
)
 
—

 
—

 
(42,460
)
Net proved reserves at December 31, 2018
614,329

 
—

 
—

 
614,329

 
United
States
 
Trinidad
 
Other
International (1)
 
Total
Natural Gas (Bcf) (3)
 
 
 
 
 
 
 
Net proved reserves at December 31, 2015
3,489.8

 
316.6

 
19.5

 
3,825.9

Revisions of previous estimates
298.4

 
29.5

 
5.2

 
333.1

Purchases in place
91.5

 
—

 
—

 
91.5

Extensions, discoveries and other additions
202.1

 
59.9

 
—

 
262.0

Sales in place
(752.0
)
 
—

 
—

 
(752.0
)
Production
(308.6
)
 
(125.1
)
 
(8.9
)
 
(442.6
)
Net proved reserves at December 31, 2016
3,021.2

 
280.9

 
15.8

 
3,317.9

Revisions of previous estimates
602.8

 
(27.4
)
 
8.6

 
584.0

Purchases in place
4.8

 
—

 
—

 
4.8

Extensions, discoveries and other additions
619.3

 
174.2

 
35.9

 
829.4

Sales in place
(56.4
)
 
—

 
—

 
(56.4
)
Production
(293.2
)
 
(114.3
)
 
(9.1
)
 
(416.6
)
Net proved reserves at December 31, 2017
3,898.5

 
313.4

 
51.2

 
4,263.1

Revisions of previous estimates
(127.2
)
 
20.7

 
15.0

 
(91.5
)
Purchases in place
41.3

 
—

 
—

 
41.3

Extensions, discoveries and other additions
951.4

 
—

 
4.6

 
956.0

Sales in place
(22.2
)
 
—

 
—

 
(22.2
)
Production
(351.2
)
 
(97.1
)
 
(11.2
)
 
(459.5
)
Net proved reserves at December 31, 2018
4,390.6

 
237.0

 
59.6

 
4,687.2

 
 
 
 
 
 
 
 
Oil Equivalents (MBoe) (2)
 

 
 

 
 

 
 

Net proved reserves at December 31, 2015
2,052,361

 
53,843

 
11,913

 
2,118,117

Revisions of previous estimates
145,542

 
4,978

 
1,722

 
152,242

Purchases in place
42,330

 
—

 
—

 
42,330

Extensions, discoveries and other additions
198,973

 
9,990

 
—

 
208,963

Sales in place
(167,669
)
 
—

 
—

 
(167,669
)
Production
(183,145
)
 
(21,150
)
 
(2,755
)
 
(207,050
)
Net proved reserves at December 31, 2016
2,088,392

 
47,661

 
10,880

 
2,146,933

Revisions of previous estimates
205,262

 
(4,493
)
 
1,249

 
202,018

Purchases in place
2,332

 
—

 
—

 
2,332

Extensions, discoveries and other additions
385,354

 
29,340

 
6,104

 
420,798

Sales in place
(20,687
)
 
—

 
—

 
(20,687
)
Production
(203,351
)
 
(19,366
)
 
(1,707
)
 
(224,424
)
Net proved reserves at December 31, 2017
2,457,302

 
53,142

 
16,526

 
2,526,970

Revisions of previous estimates
(10,500
)
 
3,272

 
2,544

 
(4,684
)
Purchases in place
11,640

 
—

 
—

 
11,640

Extensions, discoveries and other additions
668,972

 
—

 
778

 
669,750

Sales in place
(4,509
)
 
—

 
(6,310
)
 
(10,819
)
Production
(245,127
)
 
(16,478
)
 
(3,406
)
 
(265,011
)
Net proved reserves at December 31, 2018
2,877,778

 
39,936

 
10,132

 
2,927,846

 
(1)
Other International includes EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
(2)
Thousand barrels or thousand barrels of oil equivalent, as applicable; oil equivalents include crude oil and condensate, NGLs and natural gas. Oil equivalents are determined using a ratio of 1.0 barrel of crude oil and condensate or NGLs to 6.0 thousand cubic feet of natural gas.
(3)
Billion cubic feet.
Net Proved Developed and Net Proved Undeveloped Oil and Gas Reserve Quantities
 
United
States
 
Trinidad
 
Other
International (1)
 
Total
NET PROVED DEVELOPED RESERVES
 
 
 
 
 
 
 
Crude Oil (MBbl)
 
 
 
 
 
 
 
December 31, 2015
444,070

 
1,069

 
63

 
445,202

December 31, 2016
507,531

 
839

 
8,255

 
516,625

December 31, 2017
605,405

 
898

 
7,933

 
614,236

December 31, 2018
712,218

 
417

 
150

 
712,785

Natural Gas Liquids (MBbl)
 

 
 

 
 

 
 

December 31, 2015
205,898

 
—

 
—

 
205,898

December 31, 2016
230,219

 
—

 
—

 
230,219

December 31, 2017
286,872

 
—

 
—

 
286,872

December 31, 2018
341,386

 
—

 
—

 
341,386

Natural Gas (Bcf)
 

 
 

 
 

 
 

December 31, 2015
2,211.2

 
297.6

 
19.5

 
2,528.3

December 31, 2016
1,804.4

 
262.2

 
15.8

 
2,082.4

December 31, 2017
2,450.8

 
299.2

 
29.3

 
2,779.3

December 31, 2018
2,699.0

 
223.9

 
40.9

 
2,963.8

Oil Equivalents (MBoe)
 

 
 

 
 

 
 

December 31, 2015
1,018,491

 
50,677

 
3,309

 
1,072,477

December 31, 2016
1,038,483

 
44,543

 
10,880

 
1,093,906

December 31, 2017
1,300,758

 
50,779

 
12,798

 
1,364,335

December 31, 2018
1,503,441

 
37,746

 
6,950

 
1,548,137

NET PROVED UNDEVELOPED RESERVES
 

 
 

 
 

 
 

Crude Oil (MBbl)
 

 
 

 
 

 
 

December 31, 2015
643,790

 
—

 
8,604

 
652,394

December 31, 2016
660,690

 
—

 
—

 
660,690

December 31, 2017
698,666

 
—

 
71

 
698,737

December 31, 2018
819,466

 
—

 
61

 
819,527

Natural Gas Liquids (MBbl)
 

 
 

 
 

 
 

December 31, 2015
176,977

 
—

 
—

 
176,977

December 31, 2016
186,147

 
—

 
—

 
186,147

December 31, 2017
216,601

 
—

 
—

 
216,601

December 31, 2018
272,943

 
—

 
—

 
272,943

Natural Gas (Bcf)
 

 
 

 
 

 
 

December 31, 2015
1,278.6

 
19.0

 
—

 
1,297.6

December 31, 2016
1,216.8

 
18.7

 
—

 
1,235.5

December 31, 2017
1,447.7

 
14.2

 
21.9

 
1,483.8

December 31, 2018
1,691.6

 
13.1

 
18.7

 
1,723.4

Oil Equivalents (MBoe)
 

 
 

 
 

 
 

December 31, 2015
1,033,870

 
3,166

 
8,604

 
1,045,640

December 31, 2016
1,049,909

 
3,118

 
—

 
1,053,027

December 31, 2017
1,156,544

 
2,363

 
3,728

 
1,162,635

December 31, 2018
1,374,337

 
2,190

 
3,182

 
1,379,709

 
(1)
Other International includes EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
Net Proved Undeveloped Reserves
The following table presents the changes in EOG's total proved undeveloped reserves during 2018, 2017 and 2016 (in MBoe):
 
2018
 
2017
 
2016
 
 
 
 
 
 
Balance at January 1
1,162,635

 
1,053,027

 
1,045,640

Extensions and Discoveries
490,725

 
237,378

 
138,101

Revisions
(8,244
)
 
33,127

 
64,413

Acquisition of Reserves
311

 
—

 
—

Sale of Reserves
—

 
(8,253
)
 
(45,917
)
Conversion to Proved Developed Reserves
(265,718
)
 
(152,644
)
 
(149,210
)
Balance at December 31
1,379,709

 
1,162,635

 
1,053,027
Capitalized Costs Relating to Oil and Gas Producing Activities
The following table sets forth the capitalized costs relating to EOG's crude oil and natural gas producing activities at December 31, 2018 and 2017:
 
2018
 
2017
 
 
 
 
Proved properties
$
53,624,809

 
$
48,845,672

Unproved properties
3,705,207

 
3,710,069

Total
57,330,016

 
52,555,741

Accumulated depreciation, depletion and amortization
(31,674,085
)
 
(29,191,247
)
Net capitalized costs
$
25,655,931

 
$
23,364,494
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities
The following table sets forth costs incurred related to EOG's oil and gas activities for the years ended December 31, 2018, 2017 and 2016:
 
United
States
 
Trinidad
 
Other
International (1)
 
Total
2018
 
 
 
 
 
 
 
Acquisition Costs of Properties
 
 
 
 
 
 
 
Unproved (2)
$
486,081

 
$
1,258

 
$
—

 
$
487,339

Proved (3)
123,684

 
—

 
—

 
123,684

Subtotal
609,765

 
1,258

 
—

 
611,023

Exploration Costs
157,222

 
22,511

 
13,895

 
193,628

Development Costs (4)
5,605,264

 
(12,863
)
 
22,628

 
5,615,029

Total
$
6,372,251

 
$
10,906

 
$
36,523

 
$
6,419,680

2017
 

 
 

 
 

 
 

Acquisition Costs of Properties
 

 
 

 
 

 
 

Unproved (5)
$
424,118

 
$
2,422

 
$
—

 
$
426,540

Proved (6)
72,584

 
—

 
—

 
72,584

Subtotal
496,702

 
2,422

 
—

 
499,124

Exploration Costs
144,499

 
62,547

 
16,553

 
223,599

Development Costs (7)
3,590,899

 
109,491

 
16,297

 
3,716,687

Total
$
4,232,100

 
$
174,460

 
$
32,850

 
$
4,439,410

2016
 

 
 

 
 

 
 

Acquisition Costs of Properties
 

 
 

 
 

 
 

Unproved (8)
$
3,216,598

 
$
—

 
$
36

 
$
3,216,634

Proved (9)
749,023

 
—

 
—

 
749,023

Subtotal
3,965,621

 
—

 
36

 
3,965,657

Exploration Costs
156,295

 
2,695

 
6,761

 
165,751

Development Costs (10)
2,252,713

 
72,147

 
(10,984
)
 
2,313,876

Total
$
6,374,629

 
$
74,842

 
$
(4,187
)
 
$
6,445,284

 
(1)
Other International primarily consists of EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
(2)
Includes non-cash unproved leasehold acquisition costs of $291 million related to property exchanges.
(3)
Includes non-cash proved property acquisition costs of $71 million related to property exchanges.
(4)
Includes Asset Retirement Costs of $90 million, $(12) million and $(8) million for the United States, Trinidad and Other International, respectively. Excludes other property, plant and equipment.
(5)
Includes non-cash unproved leasehold acquisition costs of $256 million related to property exchanges.
(6)
Includes non-cash proved property acquisition costs of $26 million related to property exchanges.
(7)
Includes Asset Retirement Costs of $50 million, $2 million and $4 million for the United States, Trinidad and Other International, respectively. Excludes other property, plant and equipment.
(8)
Includes non-cash unproved leasehold acquisition costs of $3,102 million related to the Yates transaction.
(9)
Includes non-cash proved property acquisition costs of $732 million related to the Yates transaction.
(10)
Includes Asset Retirement Costs of $25 million, $(3) million and $(42) million for the United States, Trinidad and Other International, respectively.  Excludes other property, plant and equipment.
Results of Operations for Oil and Gas Producing Activities

Results of Operations for Oil and Gas Producing Activities (1). The following table sets forth results of operations for oil and gas producing activities for the years ended December 31, 2018, 2017 and 2016:
 
United
States
 
Trinidad
 
Other
International (2)
 
Total
2018
 
 
 
 
 
 
 
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues
$
11,488,620

 
$
302,112

 
$
155,755

 
$
11,946,487

Other
89,708

 
(49
)
 
(24
)
 
89,635

Total
11,578,328

 
302,063

 
155,731

 
12,036,122

Exploration Costs
121,572

 
21,402

 
6,025

 
148,999

Dry Hole Costs
4,983

 
—

 
422

 
5,405

Transportation Costs
742,792

 
3,236

 
848

 
746,876

Gathering and Processing Costs (3)
404,471

 
—

 
32,502

 
436,973

Production Costs
1,924,504

 
33,506

 
70,073

 
2,028,083

Impairments
344,595

 
—

 
2,426

 
347,021

Depreciation, Depletion and Amortization
3,181,801

 
91,788

 
46,687

 
3,320,276

Income Before Income Taxes
4,853,610

 
152,131

 
(3,252
)
 
5,002,489

Income Tax Provision
1,086,077

 
12,170

 
1,898

 
1,100,145

Results of Operations
$
3,767,533

 
$
139,961

 
$
(5,150
)
 
$
3,902,344

2017
 

 
 

 
 

 
 

Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues
$
7,570,768

 
$
284,673

 
$
52,450

 
$
7,907,891

Other
81,610

 
59

 
(59
)
 
81,610

Total
7,652,378

 
284,732

 
52,391

 
7,989,501

Exploration Costs
113,334

 
26,245

 
5,763

 
145,342

Dry Hole Costs
91

 
—

 
4,518

 
4,609

Transportation Costs
737,403

 
1,885

 
1,064

 
740,352

Production Costs
1,446,333

 
27,839

 
88,038

 
1,562,210

Impairments
477,223

 
—

 
2,017

 
479,240

Depreciation, Depletion and Amortization
3,157,056

 
115,174

 
24,536

 
3,296,766

Income (Loss) Before Income Taxes
1,720,938

 
113,589

 
(73,545
)
 
1,760,982

Income Tax Provision (Benefit)
625,562

 
24,882

 
(1,342
)
 
649,102

Results of Operations
$
1,095,376

 
$
88,707

 
$
(72,203
)
 
$
1,111,880

2016
 

 
 

 
 

 
 

Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues
$
5,177,989

 
$
243,708

 
$
75,046

 
$
5,496,743

Other
81,386

 
(8
)
 
25

 
81,403

Total
5,259,375

 
243,700

 
75,071

 
5,578,146

Exploration Costs
115,990

 
2,647

 
6,316

 
124,953

Dry Hole Costs
10,529

 
—

 
128

 
10,657

Transportation Costs
753,791

 
1,181

 
9,134

 
764,106

Production Costs
1,163,827

 
27,113

 
63,073

 
1,254,013

Impairments
611,297

 
7,773

 
1,197

 
620,267

Depreciation, Depletion and Amortization
3,249,792

 
145,440

 
42,052

 
3,437,284

Income (Loss) Before Income Taxes
(645,851
)
 
59,546

 
(46,829
)
 
(633,134
)
Income Tax Provision (Benefit)
(230,377
)
 
5,526

 
(1,562
)
 
(226,413
)
Results of Operations
$
(415,474
)
 
$
54,020

 
$
(45,267
)
 
$
(406,721
)
 
(1)
Excludes gains or losses on the mark-to-market of financial commodity derivative contracts, gains or losses on sales of reserves and related assets, interest charges and general corporate expenses for each of the three years in the period ended December 31, 2018.
(2)
Other International primarily consists of EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
(3)
Effective January 1, 2018, EOG adopted the provisions of Accounting Standards Update (ASU) 2014-09, "Revenue From Contracts With Customers" (ASU 2014-09). In connection with the adoption of ASU 2014-09, EOG presents natural gas processing fees relating to certain processing and marketing agreements within its United States segment as Gathering and Processing Costs instead of as a deduction to Natural Gas Revenues. There was no impact to operating income or net income resulting from changes to the presentation of natural gas processing fees (see Note 1 to Consolidated Financial Statements).
Production Costs Per Barrel of Oil Equivalent

The following table sets forth production costs per barrel of oil equivalent, excluding severance/production and ad valorem taxes, for the years ended December 31, 2018, 2017 and 2016:
 
United
States
 
Trinidad
 
Other
International (1)
 
Composite
 
 
 
 
 
 
 
 
Year Ended December 31, 2018
$
4.84

 
$
1.67

 
$
20.19

 
$
4.84

Year Ended December 31, 2017
$
4.58

 
$
1.39

 
$
50.86

 
$
4.66

Year Ended December 31, 2016
$
4.58

 
$
1.23

 
$
22.43

 
$
4.48

 
(1)
Other International primarily consists of EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves Table

The following table sets forth the standardized measure of discounted future net cash flows from projected production of EOG's oil and gas reserves for the years ended December 31, 2018, 2017 and 2016:
 
United
States
 
Trinidad
 
Other
International (1)
 
Total
2018
 
 
 
 
 
 
 
Future cash inflows (2)
$
133,066,375

 
$
749,695

 
$
303,620

 
$
134,119,690

Future production costs
(42,351,174
)
 
(204,444
)
 
(99,024
)
 
(42,654,642
)
Future development costs
(16,577,794
)
 
(78,199
)
 
(11,900
)
 
(16,667,893
)
Future income taxes
(14,756,011
)
 
(174,382
)
 
(31,748
)
 
(14,962,141
)
Future net cash flows
59,381,396

 
292,670

 
160,948

 
59,835,014

Discount to present value at 10% annual rate
(27,348,744
)
 
(26,832
)
 
(33,483
)
 
(27,409,059
)
Standardized measure of discounted future net cash flows relating to proved oil and gas reserves
$
32,032,652

 
$
265,838

 
$
127,465

 
$
32,425,955

2017
 

 
 

 
 

 
 

Future cash inflows (3)
$
83,652,363

 
$
904,141

 
$
664,560

 
$
85,221,064

Future production costs
(32,018,812
)
 
(239,213
)
 
(311,383
)
 
(32,569,408
)
Future development costs
(13,395,873
)
 
(84,379
)
 
(58,543
)
 
(13,538,795
)
Future income taxes
(5,948,453
)
 
(195,855
)
 
(16,233
)
 
(6,160,541
)
Future net cash flows
32,289,225

 
384,694

 
278,401

 
32,952,320

Discount to present value at 10% annual rate
(14,532,290
)
 
(52,267
)
 
(40,103
)
 
(14,624,660
)
Standardized measure of discounted future net cash flows relating to proved oil and gas reserves
$
17,756,935

 
$
332,427

 
$
238,298

 
$
18,327,660

2016
 

 
 

 
 

 
 

Future cash inflows (4)
$
57,913,314

 
$
524,523

 
$
402,587

 
$
58,840,424

Future production costs
(27,625,833
)
 
(165,757
)
 
(227,293
)
 
(28,018,883
)
Future development costs
(12,602,699
)
 
(103,631
)
 
(35,602
)
 
(12,741,932
)
Future income taxes
(3,151,319
)
 
(60,001
)
 
—

 
(3,211,320
)
Future net cash flows
14,533,463

 
195,134

 
139,692

 
14,868,289

Discount to present value at 10% annual rate
(6,039,736
)
 
(9,384
)
 
(7,012
)
 
(6,056,132
)
Standardized measure of discounted future net cash flows relating to proved oil and gas reserves
$
8,493,727

 
$
185,750

 
$
132,680

 
$
8,812,157

 
(1)
Other International includes EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.
(2)
Estimated crude oil prices used to calculate 2018 future cash inflows for the United States, Trinidad and Other International were $68.54, $55.66 and $61.66, respectively. Estimated NGL price used to calculate 2018 future cash inflows for the United States was $27.83. Estimated natural gas prices used to calculate 2018 future cash inflows for the United States, Trinidad and Other International were $2.50, $3.06 and $4.88, respectively.
(3)
Estimated crude oil prices used to calculate 2017 future cash inflows for the United States, Trinidad and Other International were $49.21, $41.87 and $50.06, respectively. Estimated NGL price used to calculate 2017 future cash inflows for the United States was $23.51. Estimated natural gas prices used to calculate 2017 future cash inflows for the United States, Trinidad and Other International were $1.96, $2.76 and $5.16, respectively.
(4)
Estimated crude oil prices used to calculate 2016 future cash inflows for the United States, Trinidad and Other International were $40.70, $34.79 and $39.55, respectively. Estimated NGL price used to calculate 2016 future cash inflows for the United States was $14.69. Estimated natural gas prices used to calculate 2016 future cash inflows for the United States, Trinidad and Other International were $1.40, $1.76 and $4.84, respectively.
Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Reserves
The following table sets forth the changes in the standardized measure of discounted future net cash flows at December 31, for each of the three years in the period ended December 31, 2018:
 
United
States
 
Trinidad
 
Other
International (1)
 
Total
 
 
 
 
 
 
 
 
December 31, 2015
$
8,965,467

 
$
381,124

 
$
274,805

 
$
9,621,396

Sales and transfers of oil and gas produced, net of production costs
(3,260,372
)
 
(215,414
)
 
(2,839
)
 
(3,478,625
)
Net changes in prices and production costs
(3,352,802
)
 
(182,876
)
 
(143,924
)
 
(3,679,602
)
Extensions, discoveries, additions and improved recovery, net of related costs
865,066

 
42,201

 
—

 
907,267

Development costs incurred
1,207,000

 
3,900

 
19,100

 
1,230,000

Revisions of estimated development cost
2,092,769

 
22,596

 
6,343

 
2,121,708

Revisions of previous quantity estimates
1,013,753

 
36,648

 
2,619

 
1,053,020

Accretion of discount
970,388

 
56,566

 
27,481

 
1,054,435

Net change in income taxes
738,416

 
129,622

 
—

 
868,038

Purchases of reserves in place
377,872

 
—

 
—

 
377,872

Sales of reserves in place
(375,793
)
 
—

 
—

 
(375,793
)
Changes in timing and other
(748,037
)
 
(88,617
)
 
(50,905
)
 
(887,559
)
December 31, 2016
8,493,727

 
185,750

 
132,680

 
8,812,157

Sales and transfers of oil and gas produced, net of production costs
(5,387,031
)
 
(254,948
)
 
36,649

 
(5,605,330
)
Net changes in prices and production costs
6,606,908

 
436,969

 
77,668

 
7,121,545

Extensions, discoveries, additions and improved recovery, net of related costs
3,644,041

 
270,255

 
43,952

 
3,958,248

Development costs incurred
1,435,600

 
4,700

 
—

 
1,440,300

Revisions of estimated development cost
(114,464
)
 
9,683

 
(20,096
)
 
(124,877
)
Revisions of previous quantity estimates
2,460,498

 
(58,373
)
 
36,146

 
2,438,271

Accretion of discount
849,373

 
24,066

 
13,268

 
886,707

Net change in income taxes
(1,918,989
)
 
(114,575
)
 
(10,099
)
 
(2,043,663
)
Purchases of reserves in place
30,362

 
—

 
—

 
30,362

Sales of reserves in place
(76,527
)
 
—

 
—

 
(76,527
)
Changes in timing and other
1,733,437

 
(171,100
)
 
(71,870
)
 
1,490,467

December 31, 2017
17,756,935

 
332,427

 
238,298

 
18,327,660

Sales and transfers of oil and gas produced, net of production costs
(8,416,853
)
 
(265,370
)
 
(52,399
)
 
(8,734,622
)
Net changes in prices and production costs
12,750,466

 
84,353

 
21,610

 
12,856,429

Extensions, discoveries, additions and improved recovery, net of related costs
8,418,666

 
—

 
12,287

 
8,430,953

Development costs incurred
2,732,560

 
—

 
12,600

 
2,745,160

Revisions of estimated development cost
(410,741
)
 
4,030

 
(3,814
)
 
(410,525
)
Revisions of previous quantity estimates
(173,084
)
 
39,608

 
31,750

 
(101,726
)
Accretion of discount
1,967,592

 
50,191

 
24,839

 
2,042,622

Net change in income taxes
(4,965,373
)
 
3,844

 
(11,529
)
 
(4,973,058
)
Purchases of reserves in place
116,887

 
—

 
—

 
116,887

Sales of reserves in place
(35,874
)
 
—

 
(82,058
)
 
(117,932
)
Changes in timing and other
2,291,471

 
16,755

 
(64,119
)
 
2,244,107

December 31, 2018
$
32,032,652

 
$
265,838

 
$
127,465

 
$
32,425,955

 
(1)
Other International includes EOG's United Kingdom, China, Canada and Argentina operations. The United Kingdom operations were sold in the fourth quarter of 2018. The Argentina operations were sold in the third quarter of 2016.