Study On Optimization Of Different Polymer Slug Combination In PI1~2 Layer In The Middle Of X Region

The polymer flooding industrial field test had been carried out in the PI1~4 layers in the western of X region of Daqing oilfield since 2003,and achieved good development effect.For further improving the oil production,in 2012,the EOR experiment of polymer flooding was carried out in the PI1~2 layers in the middle of X region.In the stage of blank water drive,it is found that the polymer interference from the western block is very serious,which is mainly manifested by the phenomenon of serious polymer accumulation of production wells,increasing formation pressure,decreasing the formation permeability,and injecting liquid difficulty of injection wells.At present,the research on polymer flooding interference is mainly focused on the plane interference between well patterns in a block,and there is little research on the interference of polymer flooding in tow adjacent blocks.In this paper,the STARS module of CMG software is used to carry out the historical fitting of different production stages of X.On this basis,the interference of polymer flooding development of adjacent block to the PI1~2 layers in the middle of the X region is analyzed systematically,and the different types of well groups are divided and the personalized development schemes are designed.Finally,the reasonable combination of the polymer flooding slug is optimized.The distribution of residual oil saturation in the formation is as follows: In the plane,the residual oil saturation near the side of the adjacent area is obviously reduced because of the effect of polymer,and the residual oil moves away from the side of the adjacent area,and the oil saturation of the polymer displacing front is obviously rising.In the longitudinal direction,the residual oil saturation of the thin and poor layers is higher than that of the layers with good physical property.The main distribution characteristics of polymer concentration are as follows: On the plane,it is mainly concentrated on the side adjoined with the old block.In the longitudinal direction,the polymer is more likely to advance along the layers with the connected channel sand,which has a large affecting range and high concentration.Only a few polymers enter into the thin and poor layers and have low concentration.In general,the interference of the polymer in the adjacent area occurs mainly in the channel deposit.For the above analysis results,combining the dynamic and static data and the field test results,the three types of well groups of A,B and C are divided into by taking the injection wells as the center.The injection wells with relatively low residual oil saturation,high concentration of polymer,small decrease amplitude of permeability,high current permeability and low formation pressure and the surrounding oil wells are divided into the A well group that can be injected with high concentration polymers.The injection wells with residual oil saturation dropped significantly,the most significant decrease in the concentration and range of polymer,small decrease amplitude of permeability,low current permeability and low formation pressure and the surrounding oil wells are divided into the B well group that can be injected with medium concentration polymers.The injection wells with a slight decrease of residual oil saturation and the concentration and range of polymer concentration,sharp decrease amplitude of permeability,lowest current permeability and highest formation pressure and surrounding oil wells are divided into the C well group that can be injected with low concentration polymers.For the different characteristics of the A,B and C well groups,34 development schemes are designed.According to the numerical simulation results,through the comparison of development effect and economic benefit evaluation,the combination of polymer flooding slug is optimized,which are respectively 0.4PV×500mg/L+0.667PV×300mg/L,0.3PV×400mg/L+1.4PV×200mg/L,0.3PV×300mg/L+1.55PV×200mg/L.The recovery percent of polymer flooding is 8.65%,9.45% and 8.88%,and the recovery factor is 56.82%,57.62% and 57.05%.Compared with the conventional water flooding,enhanced oil recovery values are 4.22,5.02 and 4.45 percentage points.From the whole block,the recovery percent of the optimized polymer slug combination is 9.02% and the recovery factor is 57.18%,which is 4.58 percentage points higher than that of the conventional water drive.