Pore-Throat-Adaptive Transport and Flow-Redistribution Mechanisms of Deformable Hydrogel Particles in Tight Reservoirs of the Ordos Basin

Tight reservoirs commonly exhibit strong pore-throat confinement and flow heterogeneity, which cause injected water to preferentially migrate through connected high-conductivity pathways while a large fraction of movable fluids remains under-swept. To address this limitation, deformable hydrogel particles (DHPs) with tunable particle size and network density were prepared through inverse emulsion polymerization using acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, acrylic acid, and N,N′-methylenebisacrylamide. The chemical structure, porous morphology, swelling behavior, deformation recovery, pore-throat matching, core-scale transport, and flow-redistribution performance were systematically investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), laser particle size analysis, compression testing, mercury intrusion porosimetry, nuclear magnetic resonance (NMR), micro-computed tomography (micro-CT), and core flooding. The results show that emulsification speed regulated the hydrated particle size, while crosslinking density controlled the internal network compactness and deformation capacity. The hydrated D50 values of the small-, medium-, and large-sized DHPs (DHP-S, DHP-M, and DHP-L) were 58.3 ± 3.5, 118.6 ± 6.9, and 224.7 ± 12.5 μm, respectively. Among the tested samples, DHP-M showed a balanced swelling ratio of 4.63 ± 0.31, a compressive stress of 14.8 ± 1.1 kPa at 50% strain, and an elastic recovery ratio of 81.6 ± 3.2%. A bulk strain-adjusted apparent confinement analysis identified DHP-M as providing a more suitable balance between pore entry and selective retention; however, the apparent confinement coefficient was used only as a comparative descriptor and not as a literal single-particle geometric pass/fail criterion. Core-flooding experiments further showed that DHP-M formed distributed retention in intermediate pore-throat systems and produced a residual resistance factor of 8.2. In heterogeneous parallel core systems, DHP-M preferentially retained in high-flow branches, redirecting chase water toward low-flow branches. Matched brine-only controls produced less than 2.5 percentage points of additional oil recovery, whereas DHP-M treatment increased the original oil in place (OOIP)-based recovery factor by 11.8–16.4 percentage points. This work provides a laboratory-scale pore-throat-adaptive design strategy for deformable hydrogel particles and demonstrates their potential for selective flow redistribution and sweep-efficiency improvement in tight heterogeneous reservoirs.