Abstract: The reservoir types in Tahe oilfield consist of cave，fracture，crack-cave，cave-fracture and fracture-vuggy，which
makes the problems complicated in the actual production，such as violent water flooding，stop ping blowout，production decline
and invalid coning water. We can evaluate the effect of different reservoir types or engineering measures on production
through the analysis of water flooding curve changes. The following two methods of water breakthrough speed were commonly
evaluated：1）evaluating water breakthrough speed quantitively according to the shape of production curve，and dividing oil
wells into types of slow rising，sudden rising and ，water and intermittent rising etc. 2）evaluating water breakthrough speed of
single well or wells simplely using the watercuts in two points of time. Based on the disadvantage of the conventional methods，
this paper makes a careful analysis in oil production curve，and forms a new dual water curves to analyze the well’s dynamic
production. By using a new evaluation parameter-water/oil ration(the slope of the fitting line，k)，we evaluate the speed of
water breakthrough quantitively. At last，the authors classified the water breakthrough types of the wells in No.4 block，in Tahe
Oilfield.

Key words: qualitative evaluate, water breakthrough type, water/oil ration, slope, total water, total oil, co-water floodingcurves