Producible fraction sometimes producible reserves of a fossil fuel is an engineering term that relates to the amount of a fossil fuel which can be ultimately produced with current technologies. As an engineering term, it does not take into account any business or political issues such as regulatory or economic conditions. The opposite of producible fraction is the Unproducible fraction, which may be produced in the future dependent on technological advances or geologic change. This data is compiled in engineering data, but is banned by the U.S. Securities and Exchange Commission (SEC) from company reporting. It consists of Proven reserves

Proven reserves

Proven reserves, also called proved reserves, measured reserves, 1P, and Reserves, are business or political terms regarding fossil fuel energy sources....

 often just reserves, and the vast majority of probable reserves, and minimal amounts of possible reserves.

The purely engineering term is also misleading in that squeezing the last bits of fossil fuel out follows the diminishing returns. and at some point is so costly that it becomes highly impractical, as seen on a bell curve

Bell curve

Bell curve can refer to:* A Gaussian function, a specific kind of function whose graph is a bell-shaped curve* Normal distribution, whose density function is a Gaussian function...

, which is why measures like P90 and P95 were created. Note the latter measures are considered very roughly equivalent to business terms but do not take into account business issues.