Formation temperature  before the well was put on stream: 

See also

Natural Science / Geoscience / Geology / Rock 

Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology / http://nafta.wiki/x/LYBPB

[Reservoir pressure] [Formation pressure, P_e] [Drilled formation pressure, P_d] [Startup formation pressure, P₀]

[ Initial formation pressure (P_i) ]