Abstract: Economic limit water cut has important economic significance for the development of oilfields with water injection. The industry standard selected 98% as the economic limit water cut of single well, without considering economic factors, which is obviously unreasonable. In order to reasonably determine the economic limit water cut of single well under different economic conditions and evaluate whether the production of single well has economic benefits, guided by the principle of input-output balance, a calculation model of economic limit water cut of single well in offshore waterflooding oilfield was derived for the first time based on the economic parameters such as oil price, actual output, cost and tax. Taking Bohai Q oilfield as an example, the economic limit water cut of single well was calculated under different oil prices and oil production rates, and the corresponding chart was drawn to evaluate whether the production of oil wells has economic benefits. The results show that when the cost is fixed, oil price and oil recovery rate have a great influence on the economic limit water cut, and the economic limit water cut increases with the increase of oil price and oil recovery rate. For offshore waterflooding oilfields with high oil recovery rate, the economic limit water cut is as high as 99.11% at high oil price ($100/bbl, 1 bbl=0.159 m³), which is much higher than 98% of the economic limit water cut value stipulated by the current industry standard. It prolongs the benefit production of oil wells in high water cut period, greatly improves the economic benefit of single well, and has important guiding significance for the production strategy of offshore waterflooding oilfields.

Key words: waterflooding development, input-output balance, economic limit water cut, offshore oilfield