eog resources , inc .supplemental information to consolidated financial statements ( continued ) net proved undeveloped reserves .the following table presents the changes in eog's total proved undeveloped reserves during 2017 , 2016 and 2015 ( in mboe ) : .
[['', '2017', '2016', '2015'], ['balance at january 1', '1053027', '1045640', '1149309'], ['extensions and discoveries', '237378', '138101', '205152'], ['revisions', '33127', '64413', '-241973 ( 241973 )'], ['acquisition of reserves', '2014', '2014', '54458'], ['sale of reserves', '-8253 ( 8253 )', '-45917 ( 45917 )', '2014'], ['conversion to proved developed reserves', '-152644 ( 152644 )', '-149210 ( 149210 )', '-121306 ( 121306 )'], ['balance at december 31', '1162635', '1053027', '1045640']]
for the twelve-month period ended december 31 , 2017 , total puds increased by 110 mmboe to 1163 mmboe .eog added approximately 38 mmboe of puds through drilling activities where the wells were drilled but significant expenditures remained for completion .based on the technology employed by eog to identify and record puds ( see discussion of technology employed on pages f-38 and f-39 of this annual report on form 10-k ) , eog added 199 mmboe .the pud additions were primarily in the permian basin and , to a lesser extent , the eagle ford and the rocky mountain area , and 74% ( 74 % ) of the additions were crude oil and condensate and ngls .during 2017 , eog drilled and transferred 153 mmboe of puds to proved developed reserves at a total capital cost of $ 1440 million .revisions of puds totaled positive 33 mmboe , primarily due to updated type curves resulting from improved performance of offsetting wells in the permian basin , the impact of increases in the average crude oil and natural gas prices used in the december 31 , 2017 , reserves estimation as compared to the prices used in the prior year estimate , and lower costs .during 2017 , eog sold or exchanged 8 mmboe of puds primarily in the permian basin .all puds , including drilled but uncompleted wells ( ducs ) , are scheduled for completion within five years of the original reserve booking .for the twelve-month period ended december 31 , 2016 , total puds increased by 7 mmboe to 1053 mmboe .eog added approximately 21 mmboe of puds through drilling activities where the wells were drilled but significant expenditures remained for completion .based on the technology employed by eog to identify and record puds , eog added 117 mmboe .the pud additions were primarily in the permian basin and , to a lesser extent , the rocky mountain area , and 82% ( 82 % ) of the additions were crude oil and condensate and ngls .during 2016 , eog drilled and transferred 149 mmboe of puds to proved developed reserves at a total capital cost of $ 1230 million .revisions of puds totaled positive 64 mmboe , primarily due to improved well performance , primarily in the delaware basin , and lower production costs , partially offset by the impact of decreases in the average crude oil and natural gas prices used in the december 31 , 2016 , reserves estimation as compared to the prices used in the prior year estimate .during 2016 , eog sold 46 mmboe of puds primarily in the haynesville play .all puds for drilled but uncompleted wells ( ducs ) are scheduled for completion within five years of the original reserve booking .for the twelve-month period ended december 31 , 2015 , total puds decreased by 104 mmboe to 1046 mmboe .eog added approximately 52 mmboe of puds through drilling activities where the wells were drilled but significant expenditures remained for completion .based on the technology employed by eog to identify and record puds , eog added 153 mmboe .the pud additions were primarily in the permian basin and , to a lesser extent , the eagle ford and the rocky mountain area , and 80% ( 80 % ) of the additions were crude oil and condensate and ngls .during 2015 , eog drilled and transferred 121 mmboe of puds to proved developed reserves at a total capital cost of $ 2349 million .revisions of puds totaled negative 242 mmboe , primarily due to decreases in the average crude oil and natural gas prices used in the december 31 , 2015 , reserves estimation as compared to the prices used in the prior year estimate .during 2015 , eog did not sell any puds and acquired 54 mmboe of puds. .

Question: what is the highest initial balance observed during 2015-2017?
Answer: 1149309
Explanation: it is the maximum value for this period .