Final answer:
The increasing difficulty of accessing petroleum resources correlates with the depletion of easily accessible sources and the limited extraction machinery, alongside the fact that oil buried too deep turns into gas.
Step-by-step explanation:
The section "petroleum" seems to discuss the limitations and future of fossil fuel extraction. The detail that suggests the increasing difficulty of accessing petroleum resources is the fact that we start with the easiest resources and as those are depleted, we are forced to extract from more challenging sources. This concept is outlined by the text which states that as time goes on, we have to move to the more difficult resources.
Additionally, it mentions the limited extraction machinery we possess, which restricts the rate of fossil fuel delivery from the ground. Another significant point is the limitation that petroleum buried too deep will be 'cracked' into gas, indicating a natural limit to how far we can go with current petroleum extraction technologies. Considering the alternatives, fossil fuels come out on top for several reasons.
However, issues such as finite supply and climate repercussions spur the search for other energy sources, even if they may be costlier or seen as inferior in some aspects. These elements showcased in the discussion serve to highlight the challenges we face in energy extraction and the need for exploring alternatives, as captured in the provided text.