Focused acoustic stimulation (FAS) of the bottom-hole formation zone (BHZ) is an environmentally friendly technology for increasing injectivity in injection wells and stimulation of production wells.
Decrease in bottomhole permeability is mainly due to:
- penetration of drilling fluid filtrate, mechanical impurities of injected fluid or killing fluid into the pore space of the formation; deposition of high-viscosity oil components and clay particles on the surface of pore and perforation channels;
- formation of fixed liquid films on the surface of pore channels, which include adsorption and partially diffusion sub-layers.
The effectiveness of acoustic impact on the bottomhole formation zone is due to the creation of significant inertial forces in the fluid, intense currents at solid-liquid interfaces, which are implemented in the reservoir in the form of intra-pore turbolisation of the fluid, which leads to the detachment of mechanical particles and high-viscosity deposits from the surface of perforation channels and pore space. In addition, the generation of transverse magnetohydrodynamic pressure allows increasing the effective cross-section of pore channels due to the disruption of stagnant surface liquid films. Thus, acoustic stimulation can restore or increase the permeability of the bottomhole formation zone.
The FAS technology is based on acoustic impact on the bottom-hole zone of the well and reservoir by frequencies of sound and ultrasonic ranges and promotes cleaning of perforation channels and bottom-hole zone of the reservoir from colmatising material, disruption of surface liquid layers, increase of waterflooding coverage, increase of oil displacement intensity by displacing agent, change of fluid phase permeability, acceleration of gravitational separation of oil and water.
