Problems in Applying Chemical Processes

The main technical problems associated with chemical processes include the following: (1) screening of chemicals to optimize the microscopic displacement efficiency, (2) contacting the oil in the reservoir, and (3) maintaining good mobility in order to lessen the effects of viscous fingering. The requirements for the screening of chemicals vary with the type of process. Obviously, as the number of components increases, the more complicated the screening procedure becomes. The chemicals must also be able to tolerate the environment in which they are placed. High temperature and salinity may limit the chemicals that could be used.

The major problem experienced in the field to date in chemical flooding processes has been the inability to contact residual oil. Laboratory screening procedures have developed micellar-polymer systems that have displacement efficiencies approaching 100% when sand packs or uniform consolidated sandstones are used as the porous medium. When the same micellar-polymer system is applied in an actual reservoir rock sample, however, the efficiencies are usually lowered significantly. This is due to the heterogeneities in the reservoir samples. When the process is applied to the reservoir, the efficiencies become even worse. Research needs to be conducted on methods to reduce the effect of the rock heterogeneities and to improve the displacement efficiencies.

Mobility research is also being conducted to improve displacement sweep efficiencies. If good mobility is not maintained, the displacing fluid front will not be effective in contacting residual oil.

Operational problems involve treating the water used to make up the chemical systems, mixing the chemicals to maintain proper chemical compositions, plugging the formation with particular chemicals such as polymers, dealing with the consumption of chemicals due to adsorption and mechanical shear and other processing steps, and creating emulsions in the production facilities. Research to address these operational problems is ongoing. Despite these problems, chemical flooding can be effective in the right reservoir conditions and in a favorable economic environment.