Abstract
This study explored the potential applications of three newly modified polymers [a linear polymer, a hydrophobic association of partially hydrolyzed polyacrylamide (HAHPAM), and a polymer–surfactant] as flooding agents in a specific oilfield. Rheological measurements were performed to examine the rheological performances of the three polymers under reservoir conditions. Their stability, viscoelasticity, and propagation properties were analyzed under simulated reservoir conditions. Propagation performance analyses were conducted in a sandpack model to study the propagation behavior of the three polymers in porous media. The results of the rheological study showed that the HAHPAM and polymer–surfactant exhibited high viscosity at low shear rates (deep reservoir), and all three showed acceptable viscosity with good injectivity at high shear rates (near wellbore area). In oscillatory deformation tests, the HAHPAM and polymer–surfactant showed a predominantly elastic behavior. The results of the propagation performance showed the linear polymer and polymer–surfactant could propagate well in porous media, whereas the HAHPAM showed poor propagation behavior. This finding contrasted with rheological tests in which the injectivity of HAHPAM was superior, with high viscosity at low shear rates. The results of the study provided insights either into matching the viscoelastic performance with propagation behavior in porous media, or upon analyzing the suitability of the polymers for flooding throughout a whole process under “from injectivity to propagation” considerations.
Highlights
Among the diverse enhanced oil recovery strategies, such as water flooding and gas flooding, polymer flooding is a preferable option for many oilfields
The linear polymer has a linear structure with an average relative molecular weight of 12 mDa
The linear polymer is technically mature during synthesis, and pilot tests have been performed in some oilfields, such as Daqing oilfield in China
Summary
Among the diverse enhanced oil recovery strategies, such as water flooding and gas flooding, polymer flooding is a preferable option for many oilfields. Ghoumrassi-Barr conducted studies on the feasibility of polymer flooding in a specific field according to an elaborate analysis of rheological properties in the tested polymer solutions (Sofia and Djamel 2016) Numerous rheological tests, such as dynamic viscoelastic and steady flow measurements, were performed under various polymer concentrations, salinities, reservoir temperatures, and storage times. We aim at matching the shear rate in the rheological test with the radial flow velocity in the field to characterize the properties of the polymer solution, including the injectivity near the wellbore and the viscosity retention ability in deep reservoirs. In accounting for the operational conditions of the offshore oilfields combined with the relatively high salinity of the target formation, common polymers can hardly satisfy the harsh requirements These three newly modified polymers (linear polymer, HAHPAM, and polymer–surfactant) are suggested as potential candidates for polymer flooding in the Qikou oilfield. The results for the propagation ability tested using rheological methods and the sandpack flow experiment are compared, and the corresponding microscopic mechanisms are examined in detail
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