Condensate Injury Buried Hill Gas Condensate Wells Production Performance Analysis

In recent years, with the development of oil industry in the world, a great deal of gas condensate reservoirs with industrial exploitation value has been found. As a special kind of gas reservoir, the gas condensate reservoir is possessed of unique development methods and characteristics.Compared with normal oil reservoir or gas reservoir, the flow of gas condensate system in porous medium is a quite complicated course combined with intricate phase variation. When the flowing pressure at the bottom of hole is below dew-point pressure, with the gas condensate separating out and accumulating gradually, a high oil saturation region will be formed at pre-bore, which make the gas effective permeability dimmish and the gas-well capacity fall rapidly. As the production time increasing, the region under dew-point pressure or two-phase flow in immediate vicinity of well bore expands constantly. At the same time, the condensated oil saturation at the immediate vicinity of well bore increase gradually, which cause the damaged range larger and damaged degree more seriously. These effects above have little influence on the exploitation and production in high permeability gas condensate reservoir, but it is fatal to low permeability gas condensate reservoir. Owing to the less productivity in low permeability gas condensate reservoir, the well production rate will decrease quickly and it is easy to be less than the minimum liquid carry-over velocity. As long as the gas well production rate is less than minimum liquid carry-over velocity, the condensated liquid will certainly accumulate in the well bore and the accumulated liquid become more and more as the time increasing, which cause the well stop producing on the occasion of still having certain pressure and productive capability. These phenomena often happen in the low permeability gas well. As a result, the well has to be shut down or be done some measures to unload the condensated liquid. These measures can only maintain the production temporarily but can not recovery the well productivity.Base on production performance characteristic of gas condensate reservoir and the flow theory for a gas-condensate system at constant temperature done by predecessor, this paper using experiment result done in laboratory study the formation damage of the gas condensate reservoir caused by condensated liquid and present a method of calculating and analyzing the condensated oil saturation distribution characteristic and multiphase flowcharacteristic. Taking the well of Qian 18-18 at Dagang oilfield for example, this paper also study the damage degree of the gas condensate reservoir and production performance characteristic of gas condensate reservoir, explain the reason why the low permeability gas condensate well would shut down suddenly. On the ground of analyzing all kinds of constrain condition of gas-condensate well synthetically, this paper establish a new dynamic optimum method to allocate the well production rate considering the damage of gas condensate. Using the recoverable reserve analyze method, this paper obtain the recoverable reserve regulation of Qian 18-18, which is according with practical production rate.