Supplemental Crude Oil and Natural Gas Information (Unaudited) | Supplemental Crude Oil and Natural Gas Information (Unaudited) The table below shows estimates of proved reserves prepared by the Company’s internal technical staff and independent external reserve engineers in accordance with SEC definitions. Ryder Scott Company, L.P. prepared reserve estimates for properties comprising approximately 98% , 96% , and 99% of the Company's total proved reserves as of December 31, 2018 , 2017 , and 2016 , respectively. Remaining reserve estimates were prepared by the Company’s internal technical staff. All proved reserves stated herein are located in the United States. No proved reserves have been included for the Company’s Canadian operations as of December 31, 2018 , 2017 , and 2016 . Proved reserves attributable to noncontrolling interests are immaterial and are not separately presented in the tables below. Proved reserves are estimated quantities of crude oil and natural gas which geological and engineering data demonstrate with reasonable certainty to be economically producible in future periods from known reservoirs under existing economic conditions, operating methods, and government regulations prior to the time at which contracts providing the right to operate expire, unless evidence indicates renewal is reasonably certain. There are numerous uncertainties inherent in estimating quantities of proved crude oil and natural gas reserves. Crude oil and natural gas reserve engineering is a subjective process of estimating underground accumulations of crude oil and natural gas that cannot be precisely measured, and estimates of engineers other than the Company’s might differ materially from the estimates set forth herein. The accuracy of any reserve estimate is a function of the quality of available data and of engineering and geological interpretation and judgment. Periodic revisions or removals of estimated reserves and future cash flows may be necessary as a result of a number of factors, including reservoir performance, new drilling, crude oil and natural gas prices, changes in costs, technological advances, new geological or geophysical data, changes in business strategies, or other economic factors. Accordingly, reserve estimates may differ significantly from the quantities of crude oil and natural gas ultimately recovered. Reserves at December 31, 2018 , 2017 and 2016 were computed using the 12-month unweighted average of the first-day-of-the-month commodity prices as required by SEC rules. Natural gas imbalance receivables and payables for each of the three years ended December 31, 2018 , 2017 and 2016 were not material and have not been included in the reserve estimates. Proved crude oil and natural gas reserves Changes in proved reserves were as follows for the periods presented: Crude Oil Natural Gas Total Proved reserves as of December 31, 2015 700,514 3,151,786 1,225,811 Revisions of previous estimates (99,966 ) (63,057 ) (110,474 ) Extensions, discoveries and other additions 97,587 911,062 249,430 Production (46,850 ) (195,240 ) (79,390 ) Sales of minerals in place (8,057 ) (14,733 ) (10,513 ) Purchases of minerals in place — — — Proved reserves as of December 31, 2016 643,228 3,789,818 1,274,864 Revisions of previous estimates (77,779 ) (25,390 ) (82,012 ) Extensions, discoveries and other additions 129,895 661,867 240,206 Production (50,536 ) (228,159 ) (88,562 ) Sales of minerals in place (4,365 ) (64,989 ) (15,197 ) Purchases of minerals in place 506 7,134 1,696 Proved reserves as of December 31, 2017 640,949 4,140,281 1,330,995 Revisions of previous estimates (76,994 ) (1,153,555 ) (269,253 ) Extensions, discoveries and other additions 253,066 1,871,777 565,030 Production (61,384 ) (284,730 ) (108,839 ) Sales of minerals in place (2,154 ) (35,142 ) (8,011 ) Purchases of minerals in place 3,613 52,983 12,443 Proved reserves as of December 31, 2018 757,096 4,591,614 1,522,365 Revisions of previous estimates. Revisions for 2018 are comprised of (i) the removal of 74 MMBo and 960 Bcf (totaling 234 MMBoe) of PUD reserves no longer scheduled to be drilled within five years of initial booking due to the continual refinement of the Company's drilling programs and reallocation of capital to areas providing the greatest opportunities to improve efficiencies, recoveries, and rates of return, (ii) downward revisions of 21 MMBo and 216 Bcf (totaling 57 MMBoe) from the removal of PUD reserves due to changes in anticipated well densities and other factors, (iii) upward price revisions of 21 MMBo and 31 Bcf (totaling 26 MMBoe) due to an increase in average crude oil and natural gas prices in 2018 compared to 2017, and (iv) net downward revisions of 2 MMBo and 11 Bcf (totaling 4 MMBoe) due to changes in ownership interests, operating costs, anticipated production performance, and other factors. Revisions for 2017 are comprised of (i) the removal of 89 MMBoe of PUD reserves not scheduled to be drilled within five years of initial booking due to changes in development plans, (ii) upward price revisions of 42 MMBoe due to an increase in average crude oil and natural gas prices in 2017 compared to 2016, (iii) downward revisions of 30 MMBoe due to changes in anticipated production performance, and (iv) net downward revisions of 5 MMBoe due to changes in ownership interests, operating costs, and other factors. Revisions for 2016 are comprised of (i) the removal of 70 MMBoe of PUD reserves not scheduled to be drilled within five years of initial booking due to changes in development plans, (ii) downward price revisions of 28 MMBoe due to a decrease in average crude oil and natural gas prices in 2016 compared to 2015, and (iii) net downward revisions of 12 MMBoe due to changes in ownership interests, operating costs, anticipated production performance, and other factors. Extensions, discoveries and other additions . Extensions, discoveries and other additions for each of the three years reflected in the table above were due to successful drilling and completion activities and continual refinement of our drilling programs in the Bakken, SCOOP, and STACK plays. For 2018, proved reserve additions in the Bakken totaled 176 MMBo and 448 Bcf (totaling 251 MMBoe) and reserve additions in SCOOP totaled 64 MMBo and 733 Bcf (totaling 186 MMBoe). Additionally, 2018 proved reserve additions in STACK totaled 13 MMBo and 691 Bcf (totaling 128 MMBoe). Sales of minerals in place. See Note 16. Property Dispositions for a discussion of notable dispositions in 2016, 2017, and 2018, none of which involved significant volumes of proved reserves. Purchases of minerals in place. There were no individually significant acquisitions of proved reserves in the three years reflected in the table above. The increase in acquired reserves in 2018 compared to prior years was due to higher mineral acquisition spending. The following reserve information sets forth the estimated quantities of proved developed and proved undeveloped crude oil and natural gas reserves of the Company as of December 31, 2018 , 2017 and 2016 : December 31, 2018 2017 2016 Proved Developed Reserves Crude oil (MBbl) 347,825 318,707 290,210 Natural Gas (MMcf) 1,964,289 1,699,161 1,370,620 Total (MBoe) 675,206 601,901 518,646 Proved Undeveloped Reserves Crude oil (MBbl) 409,271 322,242 353,018 Natural Gas (MMcf) 2,627,325 2,441,120 2,419,198 Total (MBoe) 847,159 729,094 756,218 Total Proved Reserves Crude oil (MBbl) 757,096 640,949 643,228 Natural Gas (MMcf) 4,591,614 4,140,281 3,789,818 Total (MBoe) 1,522,365 1,330,995 1,274,864 Proved developed reserves are reserves expected to be recovered through existing wells with existing equipment and operating methods. Proved undeveloped reserves are reserves expected to be recovered from new wells on undrilled acreage or from existing wells that require relatively major capital expenditures to recover, including most wells where drilling has occurred but the wells have not been completed. Natural gas is converted to barrels of crude oil equivalent using a conversion factor of six thousand cubic feet per barrel of crude oil based on the average equivalent energy content of natural gas compared to crude oil. Standardized measure of discounted future net cash flows relating to proved crude oil and natural gas reserves The standardized measure of discounted future net cash flows presented in the following table was computed using the 12-month unweighted average of the first-day-of-the-month commodity prices, the costs in effect at December 31 of each year and a 10% discount factor. The Company cautions that actual future net cash flows may vary considerably from these estimates. Although the Company’s estimates of total proved reserves, development costs and production rates were based on the best available information, the development and production of the crude oil and natural gas reserves may not occur in the periods assumed. Actual prices realized, costs incurred and production quantities may vary significantly from those used. Therefore, the estimated future net cash flow computations should not be considered to represent the Company’s estimate of the expected revenues or the current value of existing proved reserves. The following table sets forth the standardized measure of discounted future net cash flows attributable to proved crude oil and natural gas reserves as of December 31, 2018 , 2017 and 2016 . Discounted future net cash flows attributable to noncontrolling interests are immaterial and are not separately presented below. December 31, In thousands 2018 2017 2016 Future cash inflows $ 61,510,432 $ 42,574,897 $ 31,008,587 Future production costs (16,139,001 ) (11,159,362 ) (9,175,410 ) Future development and abandonment costs (9,706,114 ) (6,487,097 ) (6,452,647 ) Future income taxes (1) (6,012,439 ) (3,488,755 ) (3,018,839 ) Future net cash flows 29,652,878 21,439,683 12,361,691 10% annual discount for estimated timing of cash flows (13,968,061 ) (10,969,506 ) (6,851,468 ) Standardized measure of discounted future net cash flows $ 15,684,817 $ 10,470,177 $ 5,510,223 (1) Estimated future income taxes were calculated by applying existing statutory tax rates, including any known future changes, to the estimated pre-tax net cash flows related to proved crude oil and natural gas reserves, giving effect to any permanent taxable differences and tax credits, less the tax basis of the properties involved. The U.S. federal statutory tax rate utilized in estimating future income taxes was 21% at December 31, 2018 and 2017 and 35% at December 31, 2016. The weighted average crude oil price (adjusted for location and quality differentials) utilized in the computation of future cash inflows was $61.20 , $47.03 , and $35.57 per barrel at December 31, 2018 , 2017 and 2016 , respectively. The weighted average natural gas price (adjusted for location and quality differentials) utilized in the computation of future cash inflows was $3.22 , $3.00 , and $2.14 per Mcf at December 31, 2018 , 2017 and 2016 , respectively. Future cash flows are reduced by estimated future costs to develop and produce the proved reserves, as well as certain abandonment costs, based on year-end cost estimates assuming continuation of existing economic conditions. The expected tax benefits to be realized from the utilization of net operating loss carryforwards and tax credits are used in the computation of future income tax cash flows. The changes in the aggregate standardized measure of discounted future net cash flows attributable to proved crude oil and natural gas reserves are presented below for each of the past three years. December 31, In thousands 2018 2017 2016 Standardized measure of discounted future net cash flows at January 1 $ 10,470,177 $ 5,510,223 $ 6,476,284 Extensions, discoveries and improved recoveries, less related costs 5,162,635 1,462,629 786,587 Revisions of previous quantity estimates (3,522,428 ) (1,004,355 ) (794,785 ) Changes in estimated future development and abandonment costs 1,063,089 743,657 1,651,218 Sales of minerals in place, net (9,192 ) (41,077 ) (90,390 ) Net change in prices and production costs 4,224,473 3,808,116 (2,003,163 ) Accretion of discount 1,183,347 665,507 798,597 Sales of crude oil and natural gas produced, net of production costs (3,743,572 ) (2,450,474 ) (1,595,281 ) Development costs incurred during the period 1,134,153 1,045,875 454,983 Change in timing of estimated future production and other 1,324,365 948,519 (538,665 ) Change in income taxes (1,602,230 ) (218,443 ) 364,838 Net change 5,214,640 4,959,954 (966,061 ) Standardized measure of discounted future net cash flows at December 31 $ 15,684,817 $ 10,470,177 $ 5,510,223 |