Profile Control of Pam Polyacrylamide

Pam Polyacrylamide molecules interact with the rock pores' skeleton and can be retained in the rock pore structure in two ways: adsorption and trapping. Adsorption causes pam polyacrylamide molecules to stay on the surface of the pore medium, and trapping causes polymer molecules to block the channels. Both effects can reduce the water-oil mobility ratio, make the water percolation in the channel worse, and form an inactive water zone at the front edge of the oil displacement, thereby increasing the sweep coefficient. Generally speaking, adsorption is the mainstay for medium and high-permeability formations, and trapping is for low-permeability formations.

Ⅰ. The adsorption effect of pam polyacrylamide

Adsorption is the process by which pam polyacrylamide macromolecules lose their ability to flow due to hydrogen bonding, electrostatic interaction, and mechanical action of uncharged groups combining with the surface of a porous medium. During the displacement process, a large amount of dry pam polyacrylamide macromolecules will be adsorbed on the rock pore wall, effectively reducing the seepage capacity of the water phase while not affecting the seepage capacity of the oil phase, resulting in a relatively high relative permeability of the oil phase. The water phase has improved, forcing some residual oil to re-flow, improving the oil recovery. The dynamic adsorption caused by polymer flow in the pore medium of the oil layer is mainly related to polymer molecules, rock surface properties and temperature, in addition to pore structure, formation water properties, residual oil and displacement speed. The adsorption of the polymer in the porous medium reduces the permeability of the displacement phase, thereby reducing the water-oil mobility ratio.

Ⅱ. The trapping effect of pam polyacrylamide

The trapping function includes mechanical trapping and hydraulic trapping. Mechanical trapping is caused by the restriction of the flow of macromolecules in the throat of small pores. When the macromolecules become entangled at the pore throats, the dry pam polyacrylamide molecules entangle and the effective diameter increases. The likelihood of macromolecules being washed out of the pore space is significantly reduced., and finally stays in the pore space. The result is a displacement phase. The flow capacity of oil drops, and it has little effect on the flow of oil and other displaced steps. Hydraulic trapping mainly occurs in caves where the pore diameter is larger than the molecular size. It is closely related to the fluid properties and the state of macromolecules being stretched in the pores.

The hydraulic trapping process is reversible. That is when the polymer is trapped in the cave under the action of the positive displacement pressure, the permeability of the detention area decreases. When the flow direction changes and the flow velocity decreases, there is no hydrodynamic force. Drag, the pam polyacrylamide trap molecules stretch or disperse in the pore space to cause macromolecule migration. The effluent concentration can be higher than the inlet concentration at this time. Generally, hydraulic trapping occurs when the flow rate is greater than the critical velocity of the viscoelastic effect. The main reason for the occurrence is the uneven flow rate gradient of the oil layer and the migration of macromolecules, followed by the structural deviation between the macromolecular stretching concept and the curling concept.