Polymers
and viscoelastic particles are the main chemical agents
used to improve water injection profile and thus increase oil production.
In actual formations, however, there is a lack of knowledge on selecting
an appropriate chemical agent to achieve excellent conformance control
and oil production performance. To address this issue, this paper
first investigated the main rheological properties and resistance
increase performance of the two chemical agents. After that, the permeability
contrast limits for applying polymer solution and viscoelastic particle
suspension in heterogeneous reservoirs were determined through shunt
flow experiments. The critical impact of permeability contrast limits
on chemical enhanced oil recovery (EOR) was further verified via a
two-dimensional (2D) visualized oil displacement experiment. It was
found that the particles exhibit superior elasticity, while the polymers
mainly exhibit a viscosity increase effect. The resistance increase
capacity of the particle suspension in the core was more potent than
that of the polymer solution, which results in its excellent conformance
control in strongly heterogeneous cores. On the contrary, the polymer
solution might face the risk of failure. The permeability contrast
limits for applying the two chemical agents at different concentrations
were determined. Visualized oil displacement experiments showed that
the EOR by polymer flooding in strongly heterogeneous reservoirs is
quite low (3.3%). In contrast, the particle suspension could effectively
expand the swept zone and extract considerable remaining oil in the
low-permeability zones. Accordingly, the EOR could reach 7.1%. Determining
permeability contrast limits is of practical significance for selecting
suitable chemical agents to realize successful conformance control
and oil extraction in heterogeneous reservoirs.