The year is 1956. fossil fuels meant crude back then.
Since I am a honest guy, I will correct myself here. The paper actually does mention shale too in the definition of fossil fuels, but not much after that. It talks a lot about coal and natural gas, because they were relevant back then. But here is the important part:
Page 14:
"Since the production curves here considered are of CRUDE OIL only, then the pertinent reserve data must also be limited to CRUDE OIL. The data in Figure 15 represent the estimated amount of CRUDE OIL initially present which are producable by methods now in use."
Happy reading, why should I do the homework for you?