In traditional chemical EOR, water-soluble polymers for mobility control or gels for water cut reduction have been applied to improve sweep efficiency. However, since these chemicals are high environmental risks, it requires complicated applications due to the environmental regulations, and appropriate treatments to the associated water. To solve this problem, we propose a new chemical EOR method to improve the sweep efficiency, by clogging fractures or coarser pores in high-water-permeability zones using cement grout material, which had been used as an environment-friendly construction material for decades, as it had been confirmed to reduce the water permeability over a wide range by adjusting operational conditions.
To verify the effectiveness of this method, we conducted water flooding tests in homogenous artificial cores, a multi-layers cubic model, and a two-dimensional horizontal model with a high permeability channel. All cores and models were created using silica sands and powder by oil pluviation, initially saturated by diesel fuel as the alternative oil. Water with red ink was injected before and after cement grouting/curing with the appropriate pressure/rates, and had the fluid behavior was observed and measured during the injection/production.
These experiments revealed that (1) all cores and models were confirmed further oil recovery, not only during but also after the cement grouting, (2) grout particles only permeated and plugged into the high-water permeability layers/zones, performing a selective water cut, (3) some grout particles accumulated at the boundary of the high/low permeability zones, aggregating the subsequent grout injection flow into the high permeability zone, (4) flow paths of the water flooding, including the separated water from the grout suspension , were clearly diverted to the lower permeability layers/zones due to the clogging of the high permeability layers/zones, resulting in significant further oil recovery, (5) further oil recovery were also confirmed in homogeneous cores before and after grouting, suggesting other oil recovery mechanisms, such as mobility control by the grout viscosity and the ions effects in the alkalinity grout suspension.
