It is 100% clear that "reservas" refers to oil/gas reserves as per my references:
"reservas agregadas de petróleo y gas expresados en miles de barriles"
"reservas probadas desarrolladas y no desarrolladas de petróleo y gas natural"
And the reports would be presented (or submitted if you prefer) on data such as those hereunder:
The recovery factor is commonly 30-35%, giving a value for the recoverable RESERVES.
For this reason, computer modeling of economically viable reservoirs is often carried out. Geologists,[6][7] geophysicists and reservoir engineers work together to build a model which allows simulation of the flow of fluids in the reservoir, leading to an improved estimate of RESERVES.
http://en.wikipedia.org/wiki/Petroleum_reservoir#Estimating_...