Today in Russia most of large oil fields are characterized by significant recovery of reserves. Besides, a high water cut level considerably increases the amount of idle wells.
There are many methods to stimulate productive formations to enhance hydrocarbon recovery by increasing reservoir pressure, improving in-place permeability, or reducing viscosity of the produced oil. Yet, these methods have one essential disadvantage – all of them are highly specialized and target only specific problems.
In late 1990s, a group of Russian scientists headed by professor А. Molchanov launched a research program. The program’s goal was to find a source of directed impulses with power exceeding reservoir pressure. This power would create high temperature and would be capable of instantaneous compression, expansion and multiple repetition; it would also be controllable and create oscillations in gas-liquid medium with a frequency coinciding with frequencies of the productive formation’s individual layers. The task was set to enable working with any reservoirs, in wells with any water cut level.
In the course of studies and patent research, the scientists abandoned conventional methods of bottom-hole treatment and found a solution to the problem using nonlinear systems including systems with significant energy content and energy liberation, high velocity and high temperature processes, oscillations, and waves with significant amplitude.
First of all, periodic disturbances in gas-liquid medium were calculated and defined; these disturbances lead to an effect of resonance vortex formation, cavitation and flotation. As a result, liquids migrate from stagnation zones (blocks) to wells, improving in-place permeability, and concurrently treated medium is pumped with resonance energy.
This gave rise to an idea of developing a plasma impulse generator that was tested in the fields with complicated terrigenous and carbonate reservoirs in Russia, China and Kazakhstan.
Experience proved that plasma impulse excitation increases bottom-hole zone permeability and improves hydrodynamic communications between the oil formation and bottom-hole, which is also confirmed by geophysical results before and after treatment.
A distinctive feature of plasma impulse excitation is the initiation of resonance oscillations in productive formations, which prompt oil to migrate towards producing wells.
High voltage current (3,000 V) is applied to electrodes isolated by a gage wire, which results in its explosion and creation of plasma in an enclosed space.
Release of directed energy in significant quantity causes the following effect:
release of heat up to 25,000 – 28,000 С (for a period of 50-53 microseconds);
formation of a shock wave with a significant excessive pressure, which considerably exceeds the reservoir pressure;
due to processing limits a shock wave is propagated through perforations directionally along the channel profiles;
being multiply repeated, the shock wave impacts hard formation matrix in the elastic gas-liquid medium and causes longitudinal and transversal (shear) waves, which transform in a series of sequential elastic oscillations with a frequency ranging from 1 to 12,000 Hz;
being in the elastic state, the reservoir represents a combination of oscillating systems, and as a result sequential impulses cause natural formation oscillations within resonance frequencies.
A resonance effect created in the reservoir