Bohai oilfield has the characteristics of loose cementation

serious heterogeneity

high viscosity of crude oil

high average permeability and large amount of water injection in a single well. The breakthrough phenomenon of water injection development was serious

and the injection water erosion also caused damage to rock structure. Then we formed inefficient and ineffective circulation between injection and production wells

seriously affecting the effect of water flooding development

and bringing great risks to subsequent chemical flooding development. In order to satist

y the heavy oil reservoir of high water shutoff technology needs

based on the physical chemistry

polymer materials and reservoir engineering theory

and taking the chemical analysis

detection equipment and physical simulation as an experimental method

we took the reservoir rock and fluid in SZ-361 field of Bohai oilfield as the research object to study the water plugging effect and mechanism of starch graft copolymer gel. The results showed that when the water plugging agent group was

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starch（4 %）+ acrylamide（4 %） + crosslinking agent（0.036 %） + initiator（0.012 %） +anhydrous sodium sulfite（0.002 %）

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the reasonable slug size of water plugging agent was between 0.025PV and 0.075PV. For the model of

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edge water and vertical oil well

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the oil recovery of water flooding decreases with the increase of crude oil viscosity. After water plugging in the oil well

the liquid production rate decreases when the water content drops. The higher the viscosity of crude oil is

the greater the decline of water content and the recovery rate will be

but the ultimate recovery is still lower. Compared with the model of

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single water and vertical oil well

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the model of

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multilateral water and vertical oil well

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had higher water flooding recovery

and the effect of water plugging and oil increasing was better. For the high water cut development period of reservoir

due to the impact of early water flooding and chemical flooding profile control and other measures

the remaining oil saturation near the water wells borehole area was low

but the residual oil saturation in low permeability reservoirs near the wellbore was higher. Therefore

the effect of water plugging measures on increasing oil and precipitation was much better than that of profile control measures.