Potential Evaluation Study On Enhanced Oil Recovery Reservoir Of Chemical Flooding For Offshore Oilfield

With successful implement of polymer flooding technology to enhance oil recovery, it is an important way to transfer the development mode from secondary recovery to territory recovery like chemical flooding to enhance oil recovery for offshore heavy oil oilfield in the future. However, as offshore oilfield reservoir conditions are very complex, high temperature, high salinity, high oil viscosity and high cost, there is great complexity and risk for chemical flooding development. Therefore, it is necessary to carry out potential evaluation for chemical flooding reservoir of offshore oilfield so as to provide a reliable basis for policy decision of offshore oilfield efficient development. Taking Suizhong 36-1 block as example, the paper has built a set of potential evaluation method for chemical flooding reservoir in offshore oilfield.Firstly select some kind of reservoir and build numerical simulation model. And then we carried out the automatic history matching with genetic algorithm method for the water flooding development stage, which is able to rapidly obtain well-matched model without much manual intervention. On the basis of this, we have respectively established the basic schemes of the three kinds of chemical flooding including polymer flooding, polymer/ surfactant combination flooding and gel flooding. Secondly, carry out automatic history matching with genetic algorithm method. Technical and economic comprehensive evaluation result shows that polymer flooding and gel flooding can lead to better development effect.With orthogonal experimental design method, we built sample schemes for chemical flooding prediction, which can achieve scientific combination of the different influencing factors. In order to create sufficient schemes and make influencing factors combination even, the paper put forward a novel approach of orthogonal design to take the interaction into account and then verified its scientificity and rationality. For the purpose of the interaction of the influencing factors including formation temperature, formation water salinity and Calcium and Magnesium ions, the paper has built the models of the polymer viscosity for polymer flooding, the surfactant interface for polymer/surfactant flooding and polymer viscosity for gel flooding respectively. After that, with the aid of newly-built orthogonal design table and numerical simulation technology, we have separately designed potential prediction sample sets for each kind of chemical flooding.Based on potential prediction sample sets, with modified BP neural network method, we have respectively built potential prediction models for the three kinds of chemical flooding for offshore oilfield. With the models, we carried out the economic and technical potential evaluation for the different style of reservoirs in Bohai oilfield and obtained EOR, equivalent polymer injection efficient and IRR to provide the guidance and suggestion for chemical flooding implement in offshore oilfield.