LAUSR

Abstract Instrumental detection and physical simulation methods were used to study the viscosity, molecular aggregate dimension (Dh), micro-morphology, seepage characteristics, permeability limit, matching relationship between molecular dimension and radius of pore throat of rocks, and flooding effects of the amphoteric ion polymer solution (AIPS) and the amphoteric ion crosslinked polymer solution (AICPS) according to the actual needs of oilfields and in order to enhance oil recovery. It was found the crosslinking reaction of AICPS took place on a large scale in a ground flask, resulting in a great increase of viscosity. Both AIPS and AICPS had net structures. Among them, AIPS had physically crosslinked net structure, and AICPS had both chemically and physically crosslinked net structures, which were more compact. At the initial stage of solution preparation, the AIPS and AICPS had similar permeability limit. At the polymer concentration between 0 and 4000 mg/L, the AIPS and AICPS (CC = 0.2 wt%, CA = 0.02 wt%) had the minimum matching coefficient of 8.781–13.586 during injection and migration in reservoirs. AICPS showed the optimal profile control and flooding effect only within a certain range of average permeability and permeability variation coefficient of reservoirs. When three layers of heterogeneous cores had the permeability variation coefficient of 0.25, 0.59 and 0.72, respectively, the AICPS (CP = 2500 mg/L, CC = 0.2 wt%, CA = 0.02 wt%) had the average permeability of 2100 × 10−3, 3300 × 10−3 and 4100 × 10−3 µm2 at maximum enhanced oil recovery after profile control and flooding, respectively. Graphical Abstract