During thermoacoustic action, oscillations are excited in the fluid-saturated reservoir, which are accompanied by significant alternating loads and received by the saturating fluid, contributing to the following main effects:
- increase in filtration volumes of mobile fluid at the existing pore radius and pressure gradient due to the “piston” effect, which leads to an increase in fluid withdrawal;
- Involvement in the filtration process of fluid immobile at the existing pore radius and pressure gradient due to overcoming viscoplastic forces holding the fluid, which leads to intensification of oil withdrawal;
- reduction of oil viscosity due to destruction of its rheological structure by depolarization of molecules and weakening of intermolecular bonds, as a result of which phase permeability of oil increases, while for water it remains unchanged, which contributes to reduction of watercutting of production;
- overcoming surface tension forces and, accordingly, reducing the wetting angle between water and oil leads to an increase in the coefficient of oil displacement by water;
- segregation (separation) of oil and water in highly watered reservoirs due to acceleration of gravitational separation of phases of different densities in the acoustic field promotes redistribution of oil saturation and more complete oil recovery;
- manifestation of seismoelectric effect contributes to the destruction of near-wall fixed fluid layers, which have electrostatic nature and are represented by oil, so their destruction and involvement in the filtration process increases reservoir permeability and oil recovery factor;
- increase or restoration of permeability of the reservoir and bottomhole formation zone is achieved by cleaning of pore and perforation channels from mechanical impurities and high-viscosity deposits, as well as by disruption of surface liquid layers, which leads to an increase in the effective cross-section of pore channels and involvement of stagnant formation zones in the filtration process.
Viscosity reduction
High-viscosity, paraffin- and asphaltene-containing oils have viscoelastic non-Newtonian properties.
Acoustic influence changes the viscoelastic properties of the fluid in such a way that its flow approaches the flow of an ideal Newtonian fluid.
The effect is achieved by acting at the molecular level and breaking intermolecular bonds.
