Abstract: It is highly difficult to exploit a well producing from reservoir with bottom water and gas cap， because
it has characteristics of both gas cap reservoirs and bottom-water reservoirs. These reservoirs mainly produce crude
oil. During the exploitation， gas breakthrough and then bottom water coning usually take place， which shortens
period of stabilized production and leads to quick declination of production rate， and the oil recovery ratio generally
turns out to be low. But if there is non-penetrative barriers between gas/oil contact or oil/water contact of reservoir，
it will slow down the speed of gas breakthrough or bottom water coning effectively， and the period of stabilized
production for wells will be extended. But the demands of oilfield development can’t be satisfied because at present
methods of determining perforation intervals of wells in gas cap and bottom-water reservoirs fail to take all factors
into consideration or just use approximation method with plate. Besides， the influence of barriers in reservoir is
always neglected. An optimization method， which has been verified in oilfield producing， is offered to determine
optimum perforation intervals of wells in gas cap and bottom-water reservoirs.

Key words: reservoir with bottom water and gas cap, optimum perforation interval, gas cap breakthrough, bottomwater coning, barrier, optimization model