The oscillating circuits are mounted on the string with spaces sufficient for signal transmission. The interconnection of the oscillating circuits is provided by mutual induction, for example, when induction frames are properly spaced. The first oscillating circuit is installed at the well head and differs from the other oscillating circuits by the availability of a source of alternating voltage U₀ (or current) connected, for example, in parallel as shown in Fig. 2. The design of the metering oscillating circuit is shown in Fig. 3.

The data transmission algorithm is as follows. When the main oscillating circuit power source is on, oscillations of the electric current I are generated in the oscillating circuit with the frequency co₀ :

which in turn generate an alternating magnetic field the flux of which reaches the next (second) oscillating circuit in which alternating electric current of the same frequency is generated due to the oscillating circuit excitation with electromagnetic power. Under resonance conditions, the degree of interconnection between the oscillating circuits may be quite low. If the Q factors of both oscillating circuits are equal, the excitation occurs to almost the same energy level as was accumulated in the main oscillating circuit, and hence the current in the second oscillating circuit oscillates at almost the same amplitude as in the first oscillating circuit and at the same frequency a>₀. This high excitation efficiency is achieved due to the resonance in the oscillating circuits. The same effect occurs in sequence between each pair of adjacent oscillating circuits including the last one. Thus, oscillations in the system are generated in the time determined by the formula τ = RCN,

where R is determined by the effective resistance of the conductors in each oscillating circuit, C is the capacity included in each oscillating circuit and N is the number of oscillating circuits installed in the well. It should be noted that the first oscillating circuit can be installed directly at the well head. The conductor coils of that first oscillating circuit will have a greater diameter than those of the other oscillating circuits and hence the inductivity of the oscillating circuit will be different. The resonance frequency of the first oscillating circuit co₀ can be adjusted to be at the initially required level by reducing the capacitance of the capacitor.

The metering oscillating circuit is differs by the possibility of modulating and/or reflecting the signal depending on the reading of the metering device installed in the downhole region. The control signal is transmitted by the metering device, for example, by induction. Due to the small distance between the oscillating circuit and the metering device, high transmittance power of the metering device is not required.

When receiving a control signal, the adjusting unit changes the parameters of the metering oscillating circuit which in turn change its response. As the oscillating circuits are inductively interconnected, this frequency excitation is transmitted via the chain of oscillating circuits to the top of the well and can be measured in the first oscillating circuit to detect this excitation as a bit of data.

Unlike the initial system excitation, this excitation is transmitted at the speed of electromagnetic wave, i.e. almost instantaneously, and the oscillation frequency excitation can be detected in a very short time that is only limited to the order of oscillation period which can be sufficiently short if oscillating circuit parameters are properly selected.

Some possibilities of using wireless communication for the oil and gas industry will be illustrated below, though not being limited to the examples herein.

1. Logging and measurements during drilling

Currently, geophysical logging and measurements during drilling have limitations in speed and hence in the volume of data being transmitted. This requires carrying out additional geophysical well survey with flexible cables to obtain the complete set of required data.

The use of the wireless communication technology suggested herein during drilling allows obtaining the complete set of required geophysical data directly during drilling and thus avoid the necessity of additional survey after drilling. This not only reduces the time required for these operations but also avoids a number of risks and problems related to flexible cable geophysical logging.

2. Flexible pipe operations

Possible applications of the wireless communication technology suggested herein for flexible pipes may expand their application area:

- geophysical logging of complex trajectory wells or high curvature angle wells (slanted or horizontal wells) using flexible pipes and wireless communication for the power supply of logging tools and data transmission to the surface;

- well development: joint use of this wireless communication technology for the development of wells with varying geophysical properties will provide for more thorough and efficient cleaning of the bottomhole region;

- perforation: use of this wireless communication technology for depth monitoring and safe charge explosion.

3. In-operation monitoring

Installation of permanent pressure, temperature and flowrate gages and communication with these devices using this wireless communication technology will provide for well operation monitoring throughout its service life. The main advantage of this method is the possibility of installing the gages in almost any area of the well or even in the annular space of the casing string (or the liner).

Another wide application is the distributed monitoring of pressure, temperature and other properties in horizontal wells.

4. Intelligent wells

An intelligent well is a set of works and equipment for increasing and optimizing well production. This complex may comprise interval control valves, real time bottomhole control and monitoring systems and surface control system communication means. In fact, this is a well equipped with monitoring systems and production equipment components for well production optimization either automatically or with the operator's interference.

Oil and gas well and field operation practice will undergo an unparalleled breakthrough when the industry is capable of providing a set of downhole flowrate sensors equipped with controlled valves and suitable for wireless control from the surface in order to optimize well production parameters. The most critical part of this complex is the possibility of wireless communication and control of downhole tools under the conditions of strong downhole interference and losses.

Claims

What is claimed

1. Wireless power and/or data transmission system for downhole equipment monitoring and/or control comprising at least one operating downhole oscillating circuit, a first oscillating circuit comprising a power source and located at the well head, and at least one metering oscillating circuit located in the vicinity of the monitoring/control equipment and installed to allow modulating the power/signal being transmitted, wherein the distance between the adjacent oscillating circuits provides for the excitation and gain of the oscillations in the subsequent oscillating circuit.

2. System of Claim 1 wherein each oscillating circuit comprises an induction coil and a capacitor connected in parallel.

3. System of Claim 1 wherein the induction coil diameter of said first oscillating circuit is greater than the induction coil diameter of said operating oscillating circuit and said metering oscillating circuit.

4. System of Claim 1 wherein said monitoring and/or control equipment is any downhole instrumentation such as temperature gages, pressure gages, telemetry gages, flowrate meters or interval control valves.

5. System of Claim 1 wherein said metering oscillating circuit is^•capable of moving along the well shaft.

6. System of Claim 1 wherein said first oscillating circuit is capable of being connected to various surface monitoring and control devices.

7. System of Claim 1 wherein said operating oscillating circuits are mounted on the production string or integrated therewith.

8. System of Claim 1 wherein said operating oscillating circuits are mounted on the casing string or integrated therewith π

9. System of Claim 1 wherein said operating oscillating circuits are mounted on flexible flush joint pipes used for coil tubing or integrated in said flexible flush joint pipes

10. System of Claim 1 wherein said operating oscillating circuits are located inside the open well shaft.

11. System of Claim 1 wherein said operating oscillating circuits are located in or integrated with any downhole system.

12. System of Claim 1 wherein said operating oscillating circuits are located in the annular space.