Device for stimulation of wells and diagnostic method for such a stimulation device
A device ( 20 ) for stimulation of wells, includes a tool ( 200 ) including a capacitive element ( 205 ) and a stimulation head ( 210 ). The device further includes switching elements capable of placing the tool ( 200 ) in at least two states: i) a charging state in which the capacitive element and the stimulation head are electrically in series between the first terminal and the second terminal of the tool, in such a way that the electrical source charges the capacitive element through the stimulation head ( 210 ), and ii) a discharging state in which the capacitive element discharges through the stimulation head ( 210 ). Also, a diagnostic method for such a device ( 20 ) for stimulation of wells.
1. A well stimulation device comprising:
a power source connected to a first terminal and a second terminal of a tool,
said tool comprising:
a capacitive element,
a stimulation head, said stimulation head comprising a cavity inside of which are arranged a first electrode and a second electrode separated by a fluid,
a resistive element electrically in parallel with the stimulation head and, in the charging state, in series with the capacitive element, and
a switch adapted to place the tool in at least two states:
a charging state wherein a first terminal of the capacitive element is connected to the first terminal of the tool and disconnected from the second electrode, and wherein a second terminal of the capacitive element is connected to the first electrode, so that, the capacitive element and the stimulation head being electrically in series between the first terminal and the second terminal of the tool, the power source charges the capacitive element through the stimulation head, and
a discharging state wherein the first terminal of the capacitive element is connected to the second electrode, and wherein the second terminal of the capacitive element is connected to the first electrode, so that the capacitive element discharges through the stimulation head.
2. The device as claimed in claim 1 , wherein the power source is a current source.
3. The device as claimed in claim 1 , wherein the resistive element has a resistance at least two times higher than a theoretical value R F of the resistance of the fluid that separates the first electrode from the second electrode, R F being the resistance of the fluid in the absence of stimulation head damage.
4. The device as claimed in claim 1 , wherein the power source being a current source of intensity I C and the transition from the charging state to the discharging state being carried out when the voltage between the first terminal of the capacitive element and the second electrode of the stimulation head reaches a predefined upper limit value V 0 , the resistive element is of resistance R S such that the voltage R S ·I C is less than V 0 .
5. The device as claimed in claim 1 , wherein the switch is a spark-gap arranged between the first terminal of the capacitive element and the second electrode.
6. A diagnostic method of an electric well stimulation device as claimed in claim 1 , comprising:
determining a parameter representative of the resistance of the stimulation head when the tool is in the charging state wherein, the capacitive element and the stimulation head being electrically connected in series, the power source charges the capacitive element through said stimulation head,
determining a state of the stimulation head according to said parameter.
7. The method as claimed in claim 6 , wherein the determination of the parameter corresponds to a measurement of the power supplied by the power source and/or a measurement of the time required to obtain a voltage of predefined value between the first terminal of the capacitive element and the second electrode of the stimulation head.