Experimental Study On Applicability Between Hydrophobically Associating Polymer And Bohai Reservoir

Hydrophobically associating polymer(HAP) has played an important role on polymer flooding and profile control for its good properties on salt resistance. Because salt tolerance of HAP is achieved through the association among hydrophobic groups, namely change of morphology of polymer molecular aggregates, HAP is facing the problem of applicability between polymer molecular aggregates and rock pore throat, reservoir heterogeneity. In this paper, the applicability between HAP and Bohai reservoir was studied through instrumental analysis, chemical analysis and physical stimulation techniques, guided by physical chemistry, polymer materials and reservoir engineering theory, based on Bohai reservoir characteristics and fluid properties. After the compatibility between HAP and pore throat was determined, the experiment for oil displacement in heterogeneous cores indicated that there exists applicability of HAP for a heterogeneous reservoir and the applicability can be influenced by polymer concentration. The experiment for oil displacement of parallel cores demonstrated the effect of polymer concentration on the applicability of HAP for reservoir heterogeneity from two aspects of the dynamic behavior of oil displacement and the effectiveness of oil displacement. Results show that, solution viscosity, molecular clew dimension and polymer molecular aggregation state of HAP are closely related to association degree between hydrophobic groups. β-cyclodextrin can restrain the association of hydrophobic groups, which can improve the reservoir applicability of hydrophobically associating polymer. When the polymer concentration is 900mg/L, 1200mg/L, 1500mg/L, 1750mg/L and 2000mg/L, the corresponding permeability limit is 560?10-3?m2, 800?10-3?m2, 1170?10-3?m2, 1500?10-3?m2 and 1800?10-3?m2, respectively. Under the condition of polymer concentration of 1750mg/L, when the β-cyclodextrin concentration is 0%, 0.004%, 0.0065%, 0.009%, 0.016%, 0.05% and 0.08%, the corresponding permeability limit is 1500?10-3?m2, 1000?10-3?m2, 700?10-3?m2, 500?10-3?m2, 380?10-3?m2, 200?10-3?m2 and 150?10-3?m2, respectively. Mechanism study shows that, association degree between HAP molecules determines absorption of different permeability layers and profile reversal time, thus affecting the displacement effect of applicability. Therefore, when the heterogeneity of the reservoir is different, the corresponding association degree of the HAP is different too. Only when the applicability between HAP solution and reservoir heterogeneity is good, polymer solution can balance both sealing in high permeability layer and displacement in low permeability, polymer flooding can obtain optimum oil increasing effect.