Study On Polymer Flooding Technology In Sub-main Reservoirs Of Beier Block

Sabei area is located in the northern part of the Saertu Oilfield with a area of118.8km~2,a geological reserve of 61290×10~4t,a recoverable reserves of 23071×10~4t,a formation dip of 3 degrees,a average height of 150m,and has a relatively gentle structure.Its south is demarcated by 1-1row of the Sazhong area,the north and east are extended to the transition zone of the oil field and it extension of the west to the boundary of the reserves of the La and Sa oil field.The western part of the Beierxi block has undergone five major adjustments since the base well network of the main reservoir of Saertu and Putaohua was put into production in 1964.At present,there are eight well pattern nets and has many contradictions during the development process includes imperfect injection and production,large proportion of low efficiency wells,low formation pressure due to the imperfect injection production in fault areas,differences between the development of reservoirs in eastern and western parts and water imbalance in the whole area,prominent contradiction of thick oil layer after the polymer flooding,and high moisture content,difficulties for exploiting the remaining oil after polymer flooding,poorly utilized secondary reservoirs and unable to raise oil recovery significantly through conventional water flooding.In order to solve the above problems,it is necessary to carry out the fine reservoir description in the west of the Beierxi Block.According to the actual situation of the Beier area,by analyzing the production data of each layer,the sedimentary characteristics and remaining oil distribution of the two kinds of reservoirs are determined and polymer parameters optimization was carried out for sub-main reservior.On this basis,the optimization of polymer flooding and optimization of well pattern are carried out,and the development mode and effect of polymer flooding in the sub-main reservior are analyzed.It is shows that there are some remaining oil in the thin oil layer with effective thickness above 1.0m and less than 0.5m and the main adjustment target should be the oil layer with effective thickness of more than 1m.The parameters for the injection of polymer are Optimized,with a molecular weight of 3 million,a dosage of 450mg/L.PV and a concentration of single well injection between 400 and1200mg/L.In the polymer flooding well pattern,the five point area well pattern of175m is formed based on the original Portuguese one group of polymer flooding wells with a average effective thickness injection intensity of 8.2 m~3/d.m and a injection rate of 0.20PV/a.The enhanced oil recovery of the polymer flooding in the whole area is 3.7%,the cumulative oil increment is 2.0842×10~4t,and the oil content per ton of polymer is increased by 55t compared with the water flooding effect.