Abstract: In the middle-late stages of production, as the deepening of the oil field development, the marginal operation output decrease, the cost increases, and the investment increase, too. Through the analysis of the laws of the marginal operation output decreasing, the cost increasing, and the investment increasing in the middle - late stages, the operational cost is looked upon as a re-investment, by means of input and output analysis and economic limitation output calculation, the analytical model of oilwell output enhancement lim-
itation is worked out taking single well output enhancement as example, which provides alternations to economic effect analysis and shut down time of oil well production in the middle-late stages.

Key words: oil field, oil well, output enhancement, econom-ic limitation