changes in proved undeveloped reserves as of december 31 , 2013 , 627 mmboe of proved undeveloped reserves were reported , an increase of 56 mmboe from december 31 , 2012 . the following table shows changes in total proved undeveloped reserves for 2013 : ( mmboe ) .
of total proven undeveloped reserves , how much consisted of extensions discoveries and other additions?
significant additions to proved undeveloped reserves during 2013 included 72 mmboe in the eagle ford and 49 mmboe in the bakken shale plays due to development drilling . transfers from proved undeveloped to proved developed reserves included 57 mmboe in the eagle ford , 18 mmboe in the bakken and 7 mmboe in the oklahoma resource basins due to producing wells . costs incurred in 2013 , 2012 and 2011 relating to the development of proved undeveloped reserves , were $ 2536 million , $ 1995 million and $ 1107 million . a total of 59 mmboe was booked as a result of reliable technology . technologies included statistical analysis of production performance , decline curve analysis , rate transient analysis , reservoir simulation and volumetric analysis . the statistical nature of production performance coupled with highly certain reservoir continuity or quality within the reliable technology areas and sufficient proved undeveloped locations establish the reasonable certainty criteria required for booking reserves . projects can remain in proved undeveloped reserves for extended periods in certain situations such as large development projects which take more than five years to complete , or the timing of when additional gas compression is needed . of the 627 mmboe of proved undeveloped reserves at december 31 , 2013 , 24 percent of the volume is associated with projects that have been included in proved reserves for more than five years . the majority of this volume is related to a compression project in e.g . that was sanctioned by our board of directors in 2004 . the timing of the installation of compression is being driven by the reservoir performance with this project intended to maintain maximum production levels . performance of this field since the board sanctioned the project has far exceeded expectations . estimates of initial dry gas in place increased by roughly 10 percent between 2004 and 2010 . during 2012 , the compression project received the approval of the e.g . government , allowing design and planning work to progress towards implementation , with completion expected by mid-2016 . the other component of alba proved undeveloped reserves is an infill well approved in 2013 and to be drilled late 2014 . proved undeveloped reserves for the north gialo development , located in the libyan sahara desert , were booked for the first time as proved undeveloped reserves in 2010 . this development , which is anticipated to take more than five years to be developed , is being executed by the operator and encompasses a continuous drilling program including the design , fabrication and installation of extensive liquid handling and gas recycling facilities . anecdotal evidence from similar development projects in the region led to an expected project execution of more than five years from the time the reserves were initially booked . interruptions associated with the civil unrest in 2011 and third-party labor strikes in 2013 have extended the project duration . there are no other significant undeveloped reserves expected to be developed more than five years after their original booking . as of december 31 , 2013 , future development costs estimated to be required for the development of proved undeveloped liquid hydrocarbon , natural gas and synthetic crude oil reserves related to continuing operations for the years 2014 through 2018 are projected to be $ 2894 million , $ 2567 million , $ 2020 million , $ 1452 million and $ 575 million . the timing of future projects and estimated future development costs relating to the development of proved undeveloped liquid hydrocarbon , natural gas and synthetic crude oil reserves are forward-looking statements and are based on a number of assumptions , including ( among others ) commodity prices , presently known physical data concerning size and character of the reservoirs , economic recoverability , technology developments , future drilling success , industry economic conditions , levels of cash flow from operations , production experience and other operating considerations . to the extent these assumptions prove inaccurate , actual recoveries , timing and development costs could be different than current estimates. .