Publication Points of interest.
[1] Features a figure for EROEI of US oil over the period 1930-2000 from a web source, which is reproduced as Figure 1 below. 
[2] ‘The reason [for a declining EROEI of oil] is that effort is redirected to less easily accessible reserves  . . . .’
[4] ‘ EROEI  =  Produced energy/Consumed energy where produced energy is every useful energy form, while in the calculation of the consumed energy   from natural sources is not considered. The result is that energy sources with an EROEI less than 1 are not sustainable.’ 
[6] ‘The EROEI of a particular source is the ratio of the total amount of energy produced by this source  to the amount of energy required as an input to produce it.’
[7] ‘Carbon intensities of fuels are related to their EROEI  being the ratio of MJ energy output to MJ energy input for generating the output . . . .’

‘For enhanced recovery additional processes are required, decreasing the EROEI and increasing upstream carbon emissions.’
[9] ‘EROEI is defined as the ratio of gross energy produced by an energy supply process to the total (direct plus indirect) energy cost of its production  . . . .’

‘Thus the EROEI  approach provides the net energy analysis of an energy-based production process and can lead to completely different results from a pure financial assessment’
Table 1: Selected literature on EROEI.