A spark-gap of an electric arc generation device for creating a seismic wave comprises: a first electrode connected to a first electrode mounting, a second electrode connected to a second electrode mounting and having a concave surface facing the first electrode and a diameter substantially greater than the diameter of the first electrode, and at least one connection arm connecting the first electrode mounting to the second electrode mounting. The disclosure also relates to an electric arc generation device comprising such a spark-gap.

A method and system are shown that conditions an underground reservoir to cause oil and gas to increase flow, excites the conditioned underground reservoir with pressure waves to further increase flow, and recovers the oil and gas with the increased flow. The excitation may be done via one or more production wells in synchronism with excitation done via one or more conditioning wells so as to cause constructive interference of the pressure waves and further increase flow.

An electrical device for well stimulation comprising a plurality of sections configured to be assembled, end to end, to form a tool. The tool comprises first and second electrodes. The second electrode is an electrically insulated peripheral electrode of the first electrode. The first and second electrodes of the tool forming, at one of the ends of the tool, a stimulation head. Additionally, one end of a body of a first section comprises a peripheral ring that is rotatably movable and translatably immobile relative to the body of the first section. The peripheral ring comprises a thread configured to engage with a thread of the second electrode of one end of a second section.

Resonant sweeping frequencies are estimated for specific rock types, saturated with various formation fluids at reservoir conditions. A sequence and duration of resonant frequency sweeps and high amplitude low frequency vibration/agitation at each station is designed based on petrophysical and geomechanical properties, and in-situ stress conditions. Resonant sweeping and agitation is conducted as a multiple resonant frequency (fixed or variable) tool passes at optimal speed, which will be determined for specific reservoir type and downhole conditions. Resonant stimulation tool type, or combination of tools, is selected based on borehole size, reservoir parameters and resonant frequency requirements to maximize the efficiency of stimulation. Broad range of operating frequencies will allow to tune to resonant frequencies of various formation types (sandstones, limestones, shales, dolomites, and heterogeneous reservoirs comprised of the mixture of above lithologies). Low frequency transducers increase fluid displacement, and improve ultimate formation fluid recovery.

An apparatus for generating acoustic waves within a medium to stimulate oil recovery within an oil reservoir. The apparatus is operable with a single moving part—a central rotor, and the rotor further includes a “conduit” through which the supply fluid passes.

An immersible ultrasonic transmitter consists of an end element of a first type, an end element of a second type and at least one transmitting member. The end element of the first type comprises a first cylindrical transmitter, a stack of piezoelectric elements, a second cylindrical transmitter and a coupling element with a threaded connection for coupling together the two cylindrical transmitters. The transmitting member contains a stack of piezoelectric elements, a cylindrical transmitter of a transmitting member, and an element with a threaded connection for coupling together the cylindrical transmitter of a transmitting member and the cylindrical transmitter of an adjacent transmitting member, or the second cylindrical transmitter of the end element of the first type. The end element of the second type comprises a first cylindrical transmitter, a stack of piezoelectric elements and a coupling element with a threaded connection for coupling together the cylindrical transmitter and the cylindrical transmitter of an adjacent transmitting member.

A method for enhancing productivity of a stratified subterranean wellbore includes introducing a mixture including water and a first set of nanoparticles reactive to high frequency acoustic waves having a size ranging from about 10 to 100 nm to a first target zone, located in a high permeability layer of the stratified subterranean wellbore. A first stimulation including acoustic waves having a frequency range of 1 kHz to 10 kHz is provided to the first set of nanoparticles to promote reacting. Then, a mixture including water and a second set of nanoparticles having a size ranging from about 1 to 10 nm is introduced to a second target zone, located in a medium permeability layer of the stratified subterranean wellbore. A second stimulation including acoustic waves having a frequency range of 100 Hz to 1 kHz is provided to the second set of nanoparticles to promote reacting.

A downhole acoustic stimulation tool comprises: a sealed chamber containing a liquid; a pair of electrodes located in the chamber; at least one transducer arranged to generate an acoustic field between the electrodes thereby inducing cavitation in a volume of the liquid between the electrodes; and at least one capacitor configured to apply a pulse voltage across the electrodes when discharged, thereby causing the cavitating volume of liquid to form a plasma which collapses to form a shockwave. The at least one transducer constitutes a first energy source, and the at least one capacitor back and electrodes constitute a second energy source. Alternative forms and arrangements of the first and second energy sources are also disclosed.

A method for collecting data relating to characteristics of a wellbore by generating tube waves within the wellbore using an electro-hydraulic discharge (EHD) source includes generating tube waves that propagate within a fluid column of a wellbore using an EHD source, where the fluid column is defined by a casing string within the wellbore. The method also includes allowing at least a portion of the generated tube waves to interact with acoustic impedance boundaries that act as reflectors within the wellbore, creating reflected tube waves that propagate within the fluid column. The method further includes recording data corresponding to the generated tube waves and the reflected tube waves using a receiver, where the recorded data relate to characteristics of the reflectors within the wellbore.

The present disclosure discloses a rotary downhole cavitation generator, including an upper connector, a lower connector, and a casing. Said casing is internally provided with a transmission shaft, an alignment bearing, a drive assembly, a thrust bearing, a rotating disk, a rectification cylinder, an inner sleeve, and an outer sleeve. Said transmission shaft is provided with a deep hole, a diversion hole radially communicating with said deep hole, and a diversion channel radially communicating with said deep hole. Said alignment bearing and said drive assembly are sleeved on an upper end of said transmission shaft, and said rotating disk, said inner sleeve, and said thrust bearing are sleeved on a lower end of said transmission shaft. Said rectification cylinder and said outer sleeve are mounted on an inner wall of said casing, and said upper connector and said lower connector are respectively connected to both ends of said casing.