Financial report context:
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 ) : .

Financial table:
2017: balance at january 1; 2016: 1053027; 2015: 1045640; column_4: 1149309
2017: extensions and discoveries; 2016: 237378; 2015: 138101; column_4: 205152
2017: revisions; 2016: 33127; 2015: 64413; column_4: -241973 ( 241973 )
2017: acquisition of reserves; 2016: 2014; 2015: 2014; column_4: 54458
2017: sale of reserves; 2016: -8253 ( 8253 ); 2015: -45917 ( 45917 ); column_4: 2014
2017: conversion to proved developed reserves; 2016: -152644 ( 152644 ); 2015: -149210 ( 149210 ); column_4: -121306 ( 121306 )
2017: balance at december 31; 2016: 1162635; 2015: 1053027; column_4: 1045640

Additional report context:
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