The timing, by year, when our proved undeveloped reserve quantities were estimated to be converted to proved developed reserves is as follows: Our estimates of oil and natural gas reserves at December 31, 2013 include 47 Bcfe related to undrilled wells that have positive undiscounted future cash flows but which, based upon oil and natural gas prices that we use to prepare the proved reserve estimates, have a rate of return that is less than the 10% discount rate used in the Standardized Measure of Discounted Future Cash Flows attributable to the proved reserve estimates. We intend to drill the proved undeveloped wells in the time frame reflected in the estimates of proved oil and natural gas reserves as of December 31, 2013 based upon the oil and natural gas prices that we used to prepare the reserve estimates. We anticipate drilling such proved undeveloped locations based on our current development plans for our properties. Certain of these wells may be drilled to retain leasehold interests or to properly manage reservoir performance. To the extent that actual oil or natural gas prices are substantially weaker, we may have to modify our development plans or we may not fully recover our investment in drilling these wells from future cash flows. The following table presents the estimated timing of our estimated future development capital costs to be incurred for the years ended December 31, 2011, 2012 and 2013: 16 Future Development Costs Total Proved Undeveloped Reserves Year ended December 31, 2011 2012 2013 (in millions) 2012 ......................................... $ 240.2 $ — $ — 2013 ......................................... 572.3 73.6 — 2014 ......................................... 452.5 53.3 265.2 2015 ......................................... 85.2 91.8 70.6 2016 ......................................... — 130.0 24.1 2017 ......................................... — 104.7 98.1 2018 ......................................... — — 85.2 Total ....................................... $1,350.2 $ 453.4 $ 543.2 Proved Undeveloped Reserves 2011 2012 2013 Year ended December 31, Oil (MBbls) Natural Gas (MMcf) Oil (MBbls) Natural Gas (MMcf) Oil (MBbls) Natural Gas (MMcf) 2012 .................. 4,275 43,084 — — — — 2013 .................. 1,169 256,989 2,205 11,832 — — 2014 .................. 1,000 198,903 988 27,581 6,392 4,617 2015 .................. 291 35,041 845 17,624 1,328 369 2016 .................. — — 3,933 14,896 342 1,242 2017 .................. — — 2,539 3,086 — 56,129 2018 .................. — — — — — 46,018 Total ................ 6,735 534,017 10,510 75,019 8,062 108,375