2p reserves, page-8

Sloeb and Zaccc

Also to add :

1P Reserves - have a 90% chance of success (in recovering proved reserves)
2P Reserves - have a 50% chance of success (in reconvering proved + probable reserves)
3P Reserves - have a 10% chance of success (in receovering proved + probable + possible reserves)

Also, you are correct in assuming 1Bcf = 1PJ (as the energy content of natural gas varies field to field).