Unfortunately it sounds like the statistics include the CO2 produced by users of the fuel. Amount directly produced to create, transport, and leak the product would be more interesting and I think oil companies may be pretty high up there anyway, but not at 50% of all emissions (since you said that 70% manages to survive the production process). If you counted it this way then construction companies would be responsible for CO2 emitted by mixing/pouring/curing concrete, not the people digging up concrete.
It would skew a lot of things however, since a coal power plant would be responsible for all the CO2 it emits (since it's product is electricity), while if a data center instead powered itself with diesel generators it would be responsible for the CO2.