Apparatus and method for information transmission by electromagnetic waves

The present invention is in the field of well production testing drilled in a geological formation, usually to evaluate qualitatively and quantitatively the effluents contained in the geological formation traversed by the drilling. This kind of test, called "DST" for "Drill Stem Test" is usually operated in during drilling of an exploration well. However, not departing from the scope of the present invention, if these tests are performed in production wells, at the start or during the production phase.

The present invention relates to a device for transmitting, in particular real time, the information from both sides of a test valve placed in a filling tubes, commonly called test string, the gasket being inserted into a well drilled in the soil according to conventional procedures.

There are different systems to know in real time and from the surface, the pressures, temperatures, flow rates, etc. at a point of a shaft beneath a test valve while this valve can be opened or closed depending on the operational phase of this test: in flow (flowing) or pressure rise (build up).

Some systems use a hydraulic channel in the wall of the drill test, which establishes communication between the pressurized volume under test valve until the pressure measuring gauges located above the valve. Measures carried by these gauges are then transmitted to the surface via an electrical cable connected to a connection with special electronic means. The connection is made by coupling by means of a mutual inductance transformer or by a loop current.

Other systems use an acoustic transmission in the body of the train test, for example according to WO 92/06278.

The first systems have the main drawback of requiring a train test, and more specifically a test valve comprising integration of a passage hydraulic. This type of construction is very complex and expensive manufacturing and maintenance. Furthermore in such systems, the connection, electric or mutual induction, the electric cable connecting the surface to the measuring means located above the test valve is very sensitive to the nature of the fluid located inside the tube production. In particular transmission is very difficult when the fluids are conductors.

The system shown in WO 92/06278, also requires connecting electrical type between the receiver situated above the valve and the cable electric. That this binding is performed by mutual induction or by a connector electric atmosphere in a liquid ( "wet connector"), the result is the same disadvantages as other known systems.

In addition, in these solutions the transmission distance is limited practically to a length of tubing or ten meters. Therefore the connector attached to the lower end of the electrical cable must necessarily be positioned about ten meters above the test valve. In the case where the well produces a effluent containing sand, it sediments after closing the flow rate corresponding to closing the test valve, thus forming a plug which can reach several tens of meters high, which can prevent proper operation of the connector, its anchorage or undocking.

Thus, the present invention relates to an information transmission device between the bottom of a well and the ground surface, said well comprising a set of tubes separated into a lower part and an upper part by sealing means the inner space of said tubes, seal assembly means between said tubes and said well. In the device, said lower portion includes a first set comprising means for acquiring information and means for transmission and receiving electromagnetic signals, a second set of transmission and receiving electromagnetic signals is placed in the interior space of the part upper tubes by operating means comprising at least one line electrical or optical communication up to the surface and said second set includes electrical contact means with said tubes.

The first and second sets may comprise means for injecting a low frequency electric current along tubes.

The first set may include a form of toroidal transformer substantially concentric with the axis of the tubes. The second part of the transformer can be a single turn formed by the tubes looping back by the casing or by the ground.

The actuating means may be constituted by at least a length of cable coax conductors and outer metal armor.

The upper part of the tubes may include an electrical isolating means placed between two tube elements. In this case, at least one of the contact means between the second unit and the tubes is located between the insulation means and means shutter.

The means for acquiring information may include at least one sensor pressure and a temperature sensor.

The actuating means of the second set may include means to contact with the tubes in which circulates the electromagnetic current, said contacts advantageously being spaced several meters.

The well may be cased by a metal casing, and the portion of tube lying between said sets may be partially electrically insulated from said casing by centering means.

The tubes may comprise at least two electrical contact means with the metal casing, the contacts being located on either side of said portion of tubing centered.

One of the means of contact with the metal casing may be constituted by said annular sealing means.

The information acquisition means can be remotely controlled from the surface by the line channel and the electromagnetic transmission between said two sets.

The invention also relates to a method of transmitting information between the bottom of a well and the ground surface, said well having a plurality of separate tubes a lower part and an upper part by sealing means space inside said tubes, seal assembly means between said tubes and said well, means for acquiring information. In the method, it transmits a current electromagnetic carrier of said information of the lower part to the part greater by a first set under said sealing means and a second assembly disposed in the interior of the upper portion, and said information is transmitted to the surface by a line of electric or optical communication line connecting said second set to the ground surface.

The acquisition of information can be remotely controlled from the surface by the channel of said line and of second and first sets.

Can operate said second set above the sealing means by means of a coaxial cable of the type "logging".

You can communicate bi-directionally between said two sets by injecting a sinusoidal electric current of programmable intensity and frequency, frequency preferably being between 1 and 200 Hz.

The invention will be better understood and its advantages appear more clearly on reading the following examples, in no way limiting, and illustrated by the the appended figures, among which:<ul><li>1 illustrates a device of the block diagram according to the invention.</li><li>2 illustrates another implementation of the device.</li><li>Figure 3 is a diagram of an entire device.</li><li>Figure 4 shows the principle of the transmitter / receiver-type transformer.</li></ul>

In Figure 1, the object of the present invention comprises a first device 1 together with means of communication transmitter / receiver and various means measuring, in particular pressure sensors and temperature. The device comprises also a second set of communication called shuttle 2, and equipped with means transmitter / receiver complementary of the first set 1 and means of Bidirectional digital telemetry to the surface by a cable channel 3 (Type logging) with electric or fiber optic conductors. The cable 3 is maneuvered in the tubes 4 with the aid of a known surface installation technicians concerned, ie a winch and a control cab, recording and processing of signals passing through the lines of communication built into the cable 3.

The tubes 4 are lowered into a well 5 drilled through a geological layer which it is desired to produce effluents that can be contained in the pores of the layer. For this, at the end of the tubes 4 is connected a so-called test liner with the sets 1 and 2, a sealant like "packer" 6 to perform an annular seal around the tubes, a strainer 7 located below the packer and intended to allow access of the effluent towards the interior of the tubes 4, a sliding seal 8 and / or a jar mechanism ( "jar") to permit the establishment and facilitate removal packer, a test valve 9 can be opened and closed several times to open or close the communication between the geological layer and the interior of the tubes 4 in communication with the surface. Other conventional equipment not shown here, can complete the test train: connecting traffic, safety seal, etc.

In the situation shown in Figure 1, the shaft 5 is cased by a tube steel 16, usually cemented in the borehole. The link generating layer / hole gets or by perforations through the casing tube, or by a drilling 17 extending beyond the shoe of the column 16. In this configuration, the test pad comprises Preferably the contacts 10 and 11, for example in the form of leaf centralizers metal, of the packer or natural contacts provided by a set of tubes Offset in a well. It is arranged so that the contact points 10 and 11 are the most spaced as possible along the gasket, on either side of the valve 9 and at least separated more than one tube segment, that is to say at least 10 meters.

In this example, namely the transmission during a DST or any other equivalent configuration, a side to side a test valve, it is preferable to take a number of precautions so that the two links of the first set 1, constituting a transmitter / receiver-type transformer, with the contacts 10 and 11 constituting the poles are not electrically interrupted. This ensures, for example, no sliding seal type of equipment ( "slip joint") or slides ( "jar") is interposed between the two contact points 10 and 11. If it can not be otherwise, it is checked and if necessary, electrical continuity is carried out using a suitable device integrated the equipment involved "slip joint" or "jar". In addition, these precautions will use the "Packer" 6 as lower pole insofar as it practically always has anchoring dogs providing electrical contact on the column 16. In the case where Set 1 is the insulating junction type and not transformer type, there will be a Power interruption substantially in the emission dipole / receipt of all 2 and all 1, the same principle of the transmission of insulating junction types.

The assemblies 1 and 2 communicate with each other by means of currents electromagnetic guided by the casing 16 and / or the test string. generally used, the frequencies between a few Hertz and a few hundred Hertz. These waves are modulated phase shift keying (PSK in English) to carry information. The sets 1 and 2 is generally located within a casing 16, it is very advantageous to be a most extensive injection dipole can to create behind the casing a largest possible spread signal. Such a dipole is described in US-A-5394141 incorporated herein by reference. In the case where it is not possible to constitute a large dipole, the operation of this transmission device is always possible. But in this case, the transmission distance between the assembly 1 and Overall 2 and / or the data rate can be reduced to decrease the energy of noise using known principles for improving the signal to noise ratio.

In the case of formation of a large dipole, it is advantageous to avoid contact between the test string and the casing 16. protectors standard tubes can be used in rubber or other insulating ring 13 and 14 mounted on a tube element and intercalated in the test string provided at suitable distances. Note that whatever the nature of the fluid in the annular gasket / test well, including brines, the difference in conductivity between the fluid and the packing tube is a dipole apparent more than 10 meters, which is sufficient in general for this transmission.

The transmitter / receiver of each assembly 1 and 2 of this device for injected, or to receive the carrier frequency propagating along the test string can be carried out using a well known techniques, namely either such an insulating junction as disclosed in US Patent 5163714, or an extended dipole, or a transformer, the toroidal magnetic circuit surrounds the assembly 1. The winding primary comprising a number of windings adapted to the power supply, while the secondary comprises a single turn formed by the test string closing on the casing via the contacts 10 and 11.

The second transmitter / receiver 2 called shuttle, has a connection insulating 21 and a lower electrical contact means 18 with the interior of the tube 4, said means being carried out either by dogs anchored in a corresponding groove machined in a screw fitting on the tubes 4 or by removable pads remotely controlled from the surface via the electrical connection used to transfer data measured.

The second pole or pole top, the reception / transmission dipole is consisting of the metal reinforcement of the coaxial cable 3 (for example, the logging type). This cable being sufficiently centered within the tube up to a height where there is a point Contact 15, it will not be in contact with the tube wall at a distance enough large thereby achieving a dipole transmitter / receiver of great length. Of Preferably, the contact 11 is located below the contact point 15, or in the vicinity. However, if this large dipole could not be achieved, would be obtained results equivalents using a connector including an insulating junction 12 located above contact means 18 and below the contact 15 of the armature of the coaxial cable with the casing. The use of a connector having an insulating junction 12 therefore imposes the shuttle a position relative to the junction, since the switch 18 must be under the insulating coupling 12 and the contact 15 above the connector 12. Indeed, in this case, will decide the position of the insulating junction before the constitution of the surface test string to be lowered into the well. But it will be possible to install to several tens of meters above the test valve.

2 shows the configuration in which the well 20 is not cased by a steel tubing. The test string includes at least one strainer 7, a packer 6, a test valve 9 assembled to tubes 4. The first assembly 1 includes means for measures, electronic and electromagnetic means for providing communication by electromagnetic waves with the shuttle 2. The shuttle 2 is lowered into space inside the tubes, over the test valve 9, by means of a cable 3 comprising at least one line of electrical or optical communication. The set 2 or shuttle includes electrical contact means 18, preferably in the form of fingers remote or wipers. The shuttle includes an insulating connection 21 in order to constitute a first pole lower through contact 18 and a second pole with the cable armature 3. To prevent the contact of the cable reinforcement with tubes either 4 too close to the lower pole, it can if necessary encircle the cable insulation elements 22 or centering a sufficient height. It is clear that this configuration does not require precise position of the shuttle relative to the test string, unless a connection similar to the insulator 12 described in Figure 1 should be used for the purposes of a transmission even more efficient.

Figure 3 illustrates in section an embodiment of the assembly 1, the latter having at least three functions:<ul><li>measuring at least the pressure and temperature within the test valve 9,</li><li>the transmission of such data to the second unit 2 located above the test valve,</li><li>receiving and interpreting a signal from the shuttle 2.</li></ul>

Measuring pressure and temperature is provided by three gauges 30 standard, tell memory, fed by three independent sources of energy. The measures are stored in non-volatile memory programmed with a sampling frequency surface by an operator. Each gauge measures the choice, the internal pressure in the channel 31 via conduit 32 or the pressure in the annulus, that is to say outside the assembly 1. The gauges 30 are connected to an electronic cartridge 33 via an electrical connection 34. The electronic cartridge 33 retrieves data measured by one of three gauges and injects a signal in the preferred embodiment a low-frequency electromagnetic current phase modulated (PSK) representative of these data to the core 35. Figure 4 shows the principle of an embodiment and operation of a toroidal transformer, the primary circuit 40 is connected to the transmitter / receiver 33 while the secondary circuit has a single turn 41 formed by the inner shaft 42 of the assembly 1. The shaft 42 is linked mechanically and electrically trim DST and can convey the electric current to the assembly 2, thereby ensuring bi-directional communication between the assemblies 1 and 2. A cap 36 integral with the assembly 1 is electrically insulated at least on one of its ends 37 while protecting the torus 35 and the electronic cartridge 33.

In the transmission mode of a signal from the surface to the assembly 1, via the shuttle 2, a low frequency signal phase-modulated is transmitted by the shuttle. It is received by the torus 35 and processed by the electronic cartridge 33. This signal enables, for example, to change the mode of operation of the assembly 1. The two main operating modes can be:<ul><li>a mode called "Real Time" in which the data provided by one or more gauges are transmitted in real time to the shuttle, and then to the surface through the cable,</li><li>a mode called "Play-Back" by which there multiplexed type of emission data in real time and previously measured data. This mode Knowing all data measured from powering up gauges the present moment. It allows in particular to access, while the test is running, the data corresponding to the speed of said phase ( "flowing"), while the assembly 2 is generally down during the closing phase of the valve ( "build-up") that place after the well flow phase.</li></ul>

The running command signal, emitted from the surface also permits to choosing the gauge that will be read by the electronic cartridge.

It should be noted that the data is also stored in each gauge 30 and can also be read at the surface at the end of the test.

The second set or shuttle 2 (FIG 1 and FIG 2) is connected to the surface by a coaxial cable 3. The cable provides power to the electronics compartment included in the shuttle and the two-way dialogue between the shuttle and the surface.

The electronics compartment consists primarily of: a transmitter / receiver and an electromagnetic bi-directional electric transmitter for dialogue with the surface via the cable conductors.

The electromagnetic transmitter of the shuttle produces a low frequency signal phase modulated between the cable armor and the contact means 18, these two points being electrically isolated by the insulating junction 21. The shuttle generates this signal receiving a command signal from the surface via the coaxial cable. The generated signal by the shuttle is received and decoded by the unit 1 to enable it to change its operating mode. In a similar manner, the shuttle can inject or receive an electromagnetic current using means comprising a transformer.

The electromagnetic receiver of the shuttle receives and decodes the signal low frequency emitted by the assembly 1. This signal is measured between the frame and the cable 3 Contact 18. It is generally representative of the data measured by the gauges of Set 1.

When data is decoded, they are transmitted to the surface by via cable.

The contact means 18 may, in addition to providing an electrical contact between the shuttle and the test string, provide a mechanical anchoring of the shuttle in the test string. Such anchoring may be necessary if, as in the case of using an insulating connector 12 in the test string, it takes a determined position of the shuttle, or if the flow the effluent may create sudden movements or vibrations that can be embarrassing for the proper functioning of the transmission.