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In this paper, the injectivity and displacement characters of a new polymer–surfactant (SP) flooding system consisting of gemini–nonionic mixed surfactant and hydrophobically associating polyacrylamide (HAPAM) have been studied under Bohai offshore oilfield reservoir conditions. The injectivity tests have shown that the SP system could build higher resistance factor (RF) and residual resistance factor (RRF) to expand sweep efficiency in nonheterogeneous reservoirs. A total of 10 core flooding tests were carried out to investigate the effect of heterogeneity, slug composition, and polymer molecular structure. The results have shown that the system could obtain higher recovery owing to higher viscosity and ultralow interfacial tension (IFT) compare to water flooding and polymer flooding. The slug composition, with 0.175% polymer and 0.3% mixed surfactant, which forms a composite with the ratio of 4:1 gemini surfactant to nonionic surfactant, could allow full play to viscosity and IFT economically. Moreover,...

The self-assembly behavior of hydrophobically associating polyacrylamide(HAPAM)in salt solution was studied by static light scattering,dynamic light scattering,and atomic force microscopy(AFM). The apparent weight average molecular weight(Mw,a ),root mean square radius of gyration(Rg), hydrodynamic radius(Rh),and the second virial coefficient(A2),were investigated.The ratio ofRg toR h was used to determine the molecular shape of the polymer in salt solution.As the salt concentration increased,the polymer chain transformed from stretch to curl.

A fatty acid disulfonate anionic gemini surfactant was prepared and the structure of the surfactant was characterized by 1 H-NMR.Hydrophobically associating polyacrylamide was prepared according to a procedure from literature.The interaction between the hydrophobically associating polyacrylamide (HAPAM) and the anionic gemini surfactant was studied by surface/interfacial tension,apparent viscosity,and atomic force microscopy (AFM).Experimental results show that HAPAM can form a network structure in the aqueous solution by self assembly.Mixed micelles are formed by the interaction of gemini surfactant micelles and the hydrophobic microdomain of the hydrophobically associating polyacrylamide in aqueous solution,which plays a remarkable role in the surfactant and polymer assembly.Mixed micelles can enhance the inter-or intra-molecular association between the polymer molecules and the surfactant,which increases the strength of the network formed by the hydrophobically associating polyacrylamide.The apparent viscosity of the solution increased by the addition of the gemini surfactant.When the addition of the gemini surfactant exceeded a certain amount,the association between the hydrophobic groups of the polymer decreased and the network formed by hydrophobically associating interaction was weakened by the surfactant micelles,which led to a decrease in solution viscosity.The polymer also largely influenced the interfacial properties of the gemini surfactant,especially the dynamical interfacial tension.A high polymer concentration led to an increase in the time required to reach equilibrium.

Abstract As the inhibition ability is not strong enough and the tolerance ability of solid contamination is low for usual polymer drilling fluid, the amphoteric polymer drilling fluid is suggested to solve above problems after analyzing and researching interactive mechanism and components of polymer drilling fluid as well as structure character of polymer molecule. The inherent character of amphoteric polymer molecule makes it not only to have strong Inhibition but also to improve rheological property of drilling fluid. The application in 15 oilfields (nearly 4000 wells) in China demonstrates that the amphoterlc polymer drilling fluid has strong inhibition, can retard "mud-making" of shale formation, keeps low-solid content and wellbore stable. The amphoteric polymer drilling fluid has excellent rheological property to make full use of jet-bit drilling and achieve significant effectiveness of increasing drilling rate. The obvious results in protection of oil formation have been achieved. Introduction The polymer drilling fluid, in general speaking, is mud system mainly composed by linear water soluble polymers. This system is developed to satisfy the jet-bit drilling and optimum drilling requirement. In past decades, the technical development of polymer drilling fluid Is as follows:–Optimize formulation and components of drilling fluid to control solid content and distribution of solid particles.–Optimize rheological property and parameters of drilling fluid to realize reasonable distribution of pump power.–Research relationship between polymer molecular structure and it's performance and develop new types of polymer additives. In China, development of polymer drilling fluid additIves is as same as above, from simple polyacrylamide to co-polymer or ter-polymer, cationic polymer and amphoteric polymer. P. 729