Abstract: The definition of oil/gas-bearing area given in traditional petroleum
geology theory was taken objection against in this paper, The problem exists
especially in the reservoirs of overturned fold，and of fault footwall，and in
the reservoir under unconformity surface, The oil/gas-bearing areas deter-
mined by traditional methods are smaller than the actual areas, The size of
the reduced area depends on the attitudes of overturned limb of fold or fault
or unconformity surface, the, thickness of the reservoir bed and its attitude,
A more logical definition is given in this paper, The oil/gas-bearing area
should be the projected area of oil/gas-bearing body on the horizontal plane,
Three correct methods of determining the area are recommended here,

Key words: Oil/gas-bearing area Type of reservoir Oil/gas