A new method for evaluating the injection effect of chemical flooding

Hall plot analysis, as a widespread injectionevaluation method, however, often fails to achieve thedesired result because of the inconspicuous change of thecurve shape. Based on the cumulative injection volume,injection rate, and the injection pressure, this paper establishesa new method using the ratio of the pressure to theinjection rate (RPI) and the rate of change of the RPI toevaluate the injection efficiency of chemical flooding. Therelationship between the RPI and the apparent resistancefactor (apparent residual resistance factor) is obtained,similarly to the relationship between the rate of change ofthe RPI and the resistance factor. In order to estimate athief zone in a reservoir, the influence of chemical crossflowon the rate of change of the RPI is analyzed. The newmethod has been applied successfully in the western part ofthe Gudong 7th reservoir. Compared with the Hall plotanalysis, it is more accurate in real-time injection datainterpretation and crossflow estimation. Specially, the rateof change of the RPI could be particularly suitably appliedfor new wells or converted wells lacking early waterflooding history.