Abstract: Reservoir formation pressure is a very important parameter in reservoir engineering study. In Tahe oilfield, the reservoir pressure obtained from its Ordovician reservoir often appears variations in late up and early down, which bring much trouble for analysis in reservoir engineering. This paper presents a detailed interpretation of them occurred in the carbonate reservoir, according to characteristics of the Ordovician reservoir, by applying conventional reservoir engineering method intergrated with the actual reservoir feature followed by calculated formation pressure gradient that should change with formation depth from crude vertical gravitational differentiation.

Key words: Tahe oilfield, Carbonate reservoir, reservoir engineering parameter, formation pressure