Study On Adaptability Evaluation Of Polymer Flooding At Small Well Spacing In Conglomerate Reservoir

The QD1 reservoir is a typical conglomerate reservoir.Compared with conventional sandstone reservoirs,the QD1 reservoir has the characteristics of multiple pore media seepage and complex dilute pore fluidity.At the same time,the reservoir has the characteristics of thin oil layer thickness,higher plane heterogeneity and small oil well spacing.Therefore,water channeling and partial area water flooding are obvious during the water flooding development stage.It was generally shown that polymer flooding has a short effective period,large differences in polymer flooding effect,significant segregation,and high concentrations of poly concentration.In order to clarify the evaluation method and main control factors of the effectiveness and polymer production of QD1 flooding in the reservoirs,the suitability of small-distance polymer flooding in conglomerate reservoirs was studied.Firstly,according to the result of comprehensive interpretation and analysis of reservoir dynamic monitoring data,the characteristics of reservoir heterogeneity and seepage capacity of conglomerate reservoirs are clarified.Secondly,a comprehensive evaluation system suitable for polymer flooding conglomerate reservoir adaptability evaluation,Through comprehensive evaluation of polymer flooding effectiveness,polymer production characteristics and liquid production and water absorption profile evaluation,the effectiveness of polymer flooding and the difference of polymer production characteristics in each block have been identified.And the polymer production types have been classified.Then from the aspects of the static geological characteristics of the conglomerate reservoir and the dynamic characteristics of the injected polymer,an adaptive analysis of the polymer displacement of the conglomerate reservoir was conducted by using the correlation analysis method,and the main control factors of the polymer flooding effectiveness and polymer production in each zone were identified.The study shows that the conglomerate reservoir region Ⅲ has the best adaptability to polymer flooding,and the effect of polymer flooding is that the region Ⅲ > Ⅰ south > Ⅰ north > Ⅱ south > Ⅱ north.Also,the strong reservoir heterogeneity,abnormal penetration and strain characteristics of conglomerate reservoirs are the fundamental reasons for the deterioration of polymer flooding in conglomerate reservoirs In addition,initial water cut,water cut and oil production before polymer flooding,water channel heterogeneity coefficient,water invasion,and polymer production are the main controlling factors of polymer flooding effect.Injection and production pressure difference,the maximum injection rate,the water absorption index and well spacing in the polymer flooding stage are main control factors of polymer production.Finally,the adjustment countermeasures for the polymer flooding of conglomerate reservoirs are put forward.It is recommended that we should clear the heterogeneity of conglomerate before implementation of polymer flooding,also we should adopt reasonable well pattern and well spacing,and in the process of implementation we should take reasonable injection-production structure.