Research On The Evaluation Method Of Polymer Flooding Effect

Currently the water cut in many oil fields have been entering into mid-late period. As the impact of reservoir heterogeneity and unfavorable mobility ratio, there are still many remaining oil in the reservoir after the waterflooding. It is generally performed that water cut is much high,the production is low and the economical benefit is rather poor. To prove the oil field stable production,many big oilfield are generally using tertiary oil recovery to enhance the oil recovery factor and the polymer flooding is just one of the most popular method of the tertiary oil recovery.This paper takes north china oil field as example,by analyzing the polymer injection experiments of this oilfield,we studied the polymer injection influencing factors and the appraisal method of the effect of polymer injection. Finally we get following understandings:1. According to north china oil field polymer injection experiments data ,analyzing and screening ten cores of polymer injection experiments. The data include time, cumulative oil production, cumulative water production, oil saturation, permeability and so on.2. The influencing factors of polymer solution viscosity include: temperature, polymer molecular weight ,salinity and so on. The higher of polymer viscosity the better of oil displacement efficiency , the lower of polymer viscosity the worse of oil displacement efficiency. With the temperature increases the polymer viscosity decrease; with the polymer solution concentration increase the viscosity increase; with relative molecular weight increase the viscosity increase; with salinity increase the polymer solution viscosity decrease.3. The influencing factors of polymer oil displacement efficiency include geological factors, formation water, polymer self-factors and polymer injection technology.4. The laboratory test appraisal methods of polymer flooding are as follows: (1) water drive curve fitting during pre-polymer injection; (2) the improved water drive curve fitting after polymer injection; (3) grey relational analysis method ; (4) multiple linear regression method ; (5) neural network simulation. Each method has its advantage and disadvantage. The data processing and analyzing means are different, the same to the results precision. According to actual condition we choose proper laboratory test appraisal method.5. This paper summarized recovery prediction method after polymer injection, which has good precision and feasibility and provided the basis of polymer injection.