FR2703470A1 - Permanent transmitting-receiving device for monitoring an underground formation and method of implementation. - Google Patents

Abstract

- Is installed in one or more wells (1) crossing an underground zone (2) harboring for example petroleum effluents, a set of emission-reception of seismic or acoustic waves comprising one or more emission units and one or more reception units, so as to leave each well free of access for other activities linked, for example, to the production of these effluents. The transmitting and receiving units (U1-Up) are installed, for example, behind casing tubes or casings (2) or tubular columns used for other functions and connected permanently or not by cables (4) to a control and recording station (5) on the surface. These units are arranged above and below the zone to be monitored, for example, or at a distance from each other at the level of the monitored zone. They can consist, for example, of transducers which can function as transmitters and receivers such as geophones (possibly triaxial) or accelerometers associated with local control modules. With units of this type distributed over an entire portion of the well, it is possible to log the layers surrounding each well in P or S waves, at regular time intervals so as to follow, by comparison of successive records, the changes in the area monitored over time. - Application to the long-term monitoring of a deposit.

Description

The present invention relates to a transmission-reception device for

  monitor the evolution over time of an underground formation, which is permanently installed in one or more wells, as well as a method implementing the device. The device according to the invention is suitable, for example, for monitoring the evolution of a formation concealing effluents, in particular petroleum effluents, this evolution being linked, for example, to

production operations.

  The present invention finds applications in particular for monitoring an oil or gas field where the operators need to accurately monitor the evolution over time of the saturations of the fluids in an underground production zone. A known method for monitoring the evolution of a formation during production is for example to go down into observation wells distributed on a field of production, at regular intervals, the neutron logging tools and by moving the tool in the thickness of the reservoir layers, to perform logs that are interpreted in terms of saturation in

  gas and correlated with the quantities of fluid produced or injected.

  __ This process has the advantages of the mobility of the transmitters and receivers of signals used, but in return, it requires each period of investigation, that the operations that are conducted by means of

  well the time required to move the measuring probe.

  It is therefore desirable that one can carry out logging operations of a subterranean zone more or less thick, without

  to make unavailable the wells crossing this zone.

  By patents FR 2,600,172, 2,642,849, 2,681,373 (Aff 2533, 2903, 3279) of the applicant, there is a known technique to avoid the unavailability of a well which consists of SS eniel Ierlent to install a large noib sensors on the outside of tubes for casing one or more wells crossing a zone to be monitored These sensors associated with local electronic boxes, are connected by transmission lines to a control station and a surface recording A casing tube (or casing) being put in place, the sensors that are found in the annular space between it and the well, are coupled with the formations surrounding the well by the sealing cement This technique of installation and coupling allows to passive listening spontaneously emitted sounds by training during production or even to conduct seismic prospecting operations by recording the signals received by the various sensors in in response to acoustic or seismic waves emitted in the formation by a source disposed on the surface It is also possible to use a well source that is lowered into another well or possibly into the same well, but this arrangement makes the well unavailable, is not compatible with a

long-term monitoring.

  The acoustic-emission or seismic transmission device of permanent character according to the invention makes it possible to follow the evolution over time of an underground formation. It is characterized in that it comprises in combination a transmitting and receiving assembly. acoustic or seismic waves permanently installed in at least one well, comprising at least one emission unit and at least one reception unit arranged at different depths so as to be coupled with the lands surrounding said well while leaving it free for another activity (related in particular to the production of the training), a control and recording station comprising a control unit for 3 O successively control the emission of acoustic or seismic waves by several emission units of the transmission and reception system and a transmission system for

  connect the station to the transmitting and receiving ensemble.

  The transmission-reception assembly comprises, for example, several transmission and reception units distributed over a portion of length of at least one well and arranged alternately. The emission-receiving set may also include

  units distributed in several wells.

  According to one embodiment, each transmission unit is associated with a local control module and in this case, the transmitting and receiving unit may comprise several transmission / reception groups arranged at different depths in the well, each of them being adapted to emit and receive acoustic or seismic waves and being associated with

a local interface module.

  Each transmission-reception group comprises, for example

  At least one transceiver transducer.

  According to one embodiment, each transceiver transducer is a geophone or an accelerometer and preferably the device comprises means for applying to the transmission units signals whose

frequency varies over time.

  According to a possible arrangement, at least a portion of the transmitting and receiving units are arranged in at least one well provided with a casing tube in the annular space.

  between him and the well and drowned in sealing cement.

  According to another arrangement, at least part of the transmitting and receiving units are disposed outside a tube placed in at least one well and connected to it by connecting means allowing acoustic decoupling by

compared to the tube.

  The investigative method according to the invention makes it possible to follow the evolution over time of an underground formation by means of acoustic or seismic waves. It is characterized in that it comprises in combination: 1) the installation; fixed station in at least one well drilled through the subterranean formation, a set of emission and reception of acoustic or seismic waves comprising at least one transmission unit and at least one reception unit arranged at different depths, this set being arranged to be coupled with the lands surrounding the well while leaving it accessible (for an activity related to the production of the formation for example), 2) the realization of cycles of transmission-reception comprising 1 O each: a) the emission of waves by the emission unit successively by several of said transmission units situated at different depths; as well as b) the reception of the waves emanating from the formation in response to the successive transmissions and their recording; and 3) a comparison of recordings made in successive cycles so as to highlight training changes over time as a result of

effluent production.

  With certain configurations of transmission and reception units, in some cases a logging of the formations surrounding the wells is carried out.

  carries out well-to-well seismic prospecting operations.

  With the device according to the invention can therefore according to the arrangement used, perform all kinds of seismic prospecting operations or logging, and this without ever interfere

  the operation of the supervised area.

  Other features and advantages of the device according to the invention and of the method of implementation will appear

  3 O better reading the following description of modes of

  embodiment described by way of non-limiting example, with reference to the accompanying drawings where F 1% is schematically a first embodiment of the device with a transmission-reception assembly

2703470

  acoustic or seismic waves having at least one emission unit and at least one receiving unit permanently installed at different depths behind a casing tube and coupled with the formations by sealing cement; FIG. 2 diagrammatically shows a second embodiment where the transmission-reception assembly comprises, for example, two transmission units and two reception units which are arranged at intervals of one another along a tube and positioned in a well at different depths, by placing the tube therein; FIG. 3 diagrammatically shows a variant of the embodiment of FIG. 1, where a set of emission units and reception units arranged behind a casing tube are arranged at a zone to be monitored, remote from each other and alternately, a transmission unit being interposed between two successive reception units; Fig 4 schematically shows an arrangement similar to the previous applied to the embodiment of Fig 2; FIG. 5 shows a variant of the embodiment of FIG. 1. the transmission and reception units used are transducers capable of operating as wave transmitters as in receivers, this variant also being applicable to the embodiment of FIG. Fig 2; and FIG. 6 schematically shows a box for three transducers whose axes are oriented in three orthogonal directions, which can be used to emit

  waves and capture the induced wave components received.

  The method according to the invention is implemented by means of a transmission-reception unit arranged at a fixed station in at least one well passing through a subterranean formation concealing, for example, petroleum effluents and coupled with the formations surrounding the well. , to allow free access to the well for any other activity. This set includes a fixed number p of acoustic and seismic emission and reception units, and is connected by a transmission system comprising one or more transmission cables,

  at a central control and recording station.

  The transmitting and receiving units U1, U2, Uk Up can be fixedly installed in a well 1 according to a technique described in French Patents 2,600,172, 2,642,849, 2,681,373 (Aff. 2533, 2903, 3279) already mentioned The units P u to Up are positioned behind a casing tube or casing 2 which is then lowered into the well Preferably the units are placed in housings (not shown in the figure) arranged for this purpose The cement that then injected into the space 3 between the tube and the walls of the well, provides the acoustic coupling of the transmitting and receiving units with the surrounding formations The transmitting and receiving units (U-Up) are permanently connected by a transmission system comprising at least one cable 4, to a surface station 5 comprising a control unit (Uc) and a recording assembly SR. In all cases, the positioning of the emission package reception outside

  of the tube, leave the well free for other uses.

  According to the embodiment of FIG. 2, a transmitting-receiving assembly comprising a given number p of units U1, U2, Uk, Up is installed at a fixed station according to a technique described for example in patents FR 2 656. 034, 2 674 029 (Aff 3007, 3190 Czernichow, Laurent) These units are associated with

  a tubular column 6 which is lowered into a well casing.

  They are pressed in operation against the casing tube so as to improve their coupling with the formations surrounding the well. Connecting means 7 connect the different units to the surface station 5. Again, the positioning of the transmission unit receiving outside the tubular column 6, leaves the free well of avccs for

other uses.

  Preferably, the transmission system comprises electronic modules (not shown) associated with the receiving units They are fed from the surface station 5 and adapted to digitize the received signals and transmit them in coded form for their recording. The units U1 to U1 may be installed on either side of the portion of the well passing through the zone Z and / or along this portion of the well. One or more of these units are transmitters of seismic or acoustic waves. many

  1 O of them are receivers of these same waves.

  In its simplest configuration, the device according to the invention comprises a transmission-reception set of waves

  acoustic or seismic consists of two units Ul and U 2.

  One of the units Ul is a transmission unit disposed in the well above the area to be monitored, for example, the other unit U 2 being a receiving unit that is disposed below

this same area.

  By operating at intervals the transmission unit U1 if it is unique or each of them if the set comprises several, it is possible to record at station 5 the induced P or S waves received by the reception unit U 2 or each of them, and by comparisons between successive record sets, determine for example the variations in time, the

  gas saturation of the formations crossed.

  According to the variants of the embodiments of FIGS. 1 and 2 respectively, schematized in FIGS. 3 and 4, the transmission / reception assembly may comprise, for example, transmission and reception units R1, E1, R2, E2, Rn. , Arranged alternately and at regular intervals along the well portion

crossing the Z zone to be monitored.

  With such an arrangement, it is possible to carry out an acoustic logging of the zone Z in P or S waves. Each emitter El to En is activated in succession and the induced waves returned by the formation are received on the neighboring receivers of each of them. determine for example the variations at

  during the time of the saturation of the rocks in gas.

  A practical embodiment of the transmission-reception assembly consists for example in setting up transducers ER 1, E Rk-1, E Rk, E Rk + 1 E Rp, (FIG. 5) capable of functioning as well. in transmitters than in acoustic or seismic wave receivers Each transducer E Rk emits a signal successively and the induced signals are received by the

  two adjacent transducers E Rk 1 and E Rk + 1 for example.

  As transducers, it is possible to use, for example, geophones which are made to operate in vibrators. The energy they can radiate being small, they are preferably supplied with power.

  with a vibratory signal whose frequency varies over time.

  The duration of transmission of the variable frequency signal is determined according to the power that can radiate the chosen transducer, so as to obtain

exploitable records.

  Although their electrical impedance is generally much greater than that of the geophones, it is nevertheless possible to use accelerometers of the same type.

piezoelectric for example.

  A control mode of each transmission unit and in particular of each transducer used as a transmitter consists of

  generate in situ the emission signals.

  The transmission system comprises in this case local signal generators (not shown) supplied with electrical energy from the surface station 5, these generators being adapted to generate the signal to be transmitted as a function of coded signals received by transmission lines in cable 4 (Fig 1, 3 O 2) Depending on the case, the signal applied to each transducer may

be impulse or continuous.

  A link system allowing the b-direction communications between the different units of the transceiver assembly and the surface station 5 and the transmission of electrical energy to the transmission units is described for example in French patent applications FR 91/15 691,

  92/03 575 (Aff 3317, 3364 Staron, Cretin) of the applicant.

  To interconnect the different transmitting and receiving units, it is also possible to use lines running in hydraulic lines, according to the technique described in FIG.

  FR 91/15483 (Aff 3315 J Laurent).

  A transceiver assembly permanently connected to the surface station 5 has been described. This connection to the station 5 of the transceiver units can, however, also be carried out discontinuously only during the periods of time. seismic observation of the zone Z, according to the technique described in patent FR 92/02 201 (Aff 3349 P Meynier) of the applicant. Embodiments have been described where the transceiver assembly is placed in a single well. It is obvious, however, that the transmitting and receiving units can be distributed in several wells traversing the area to be monitored, so that to do seismic prospecting from wells to

well.

Claims (9)

  1) Acoustic or seismic emission-reception device of a permanent nature, for monitoring the evolution over time of an underground formation, characterized in that it comprises in combination a set of transmission and reception of waves acoustic or seismic (Ul-Up) permanently installed in at least one well (1), comprising at least one emission unit and at least one reception unit arranged at different depths 1 O so as to be coupled with the grounds surrounding said well while leaving it free for another activity, a control and recording station (5) comprising a control unit (Uc) for successively controlling the emission of acoustic or seismic waves by several emission units of the transmission and reception assembly and a transmission system (4, 7) for connecting the   station to the transmitting and receiving set.   2) Device according to claim 1, characterized in that the transmission-reception assembly (U 1-Up) comprises a plurality of transmission and reception units distributed over a portion of   length of at least one well and arranged alternately.   3) Device according to one of the preceding claims,   characterized in that the transceiver assembly comprises   units distributed in several wells.   4) Device according to one of the preceding claims,   characterized in that each transmission unit (U) is associated with a local control module.   ) Device according to the preceding claim, characterized in that the transmission and reception assembly comprises 3 O several groups (E, R) transmission-reception arranged at different depths in the well, each of them being adapted to emit and receive acoustic or seismic waves and   being associated with a local module u'iiterface.   1 1 6) Device according to the preceding claim, characterized in that each transmission-reception group comprises at least   a transceiver transducer (ERJ-E Rp).   7) Device according to the preceding claim, characterized in that each transceiver transducer is a geophone. 8) Device according to claim 6, characterized in that   each transceiver transducer is an accelerometer.   9) Device according to one of the preceding claims,   1 O characterized in that it comprises means for applying to said transmission units signals whose frequency varies at course of time.   Device according to one of the preceding claims,   characterized in that at least part of the transmitting and receiving units is disposed in at least one well provided with a casing tube (2) in the annular space (3) between it and the casing   well (1) and embedded in cementitious cement.   11) Device according to one of the preceding claims,   characterized in that at least a portion of the transmitting and receiving units are disposed outside a tubular colone (6) placed in at least one well and connected thereto by connecting means allowing a acoustic decoupling by to said column.   12) Investigation method for monitoring the evolution over time of an underground formation by means of acoustic or seismic waves, characterized in that it comprises in combination: 1) the stationary installation in at least one a well drilled through the subterranean formation, an emission and acoustic reception assembly (UI-Up) comprising at least one transmission unit and at least one reception unit arranged at different depths, this assembly being arranged to be coupled with-ec the terrain surrounding the well (1) while leaving it accessible; 2) carrying out transmission-reception cycles each comprising: a) the emission of waves by each transmission unit as well as b) the reception of the waves emanating from the formation in response to the successive transmissions and their recording; and 3) a comparison of recordings made in successive cycles to highlight training changes over time as a result of production. effluents.   1 O 13) Method according to the preceding claim, characterized in that the transmission and reception assembly comprising several transmission-reception groups (R, E) arranged at different depths along at least one well. in a portion thereof passing through an area of the subsoil, the realization of said transmission-reception cycles consists of a logging of the formations in said portion by successively activating the different transmission-reception groups to transmit waves to   different locations along the well.   14) Method according to the preceding claim, characterized in that each transmission-reception group consisting of a transducer that can operate alternately transmitter and receiver is made a disgraphy of the formations traversed by the well portion by activating successively all transducers by means of variable frequency signals and the signals induced by the other transducers.   A method according to claim 12, characterized in that the transmission and reception assembly comprises a plurality of emission units disposed at different depths along at least one first well in a portion thereof. passing through an area of the subsoil, and several reception units distributed at different depths along at least one second well, the realization of emission-reception cycles comprises a successive activation of different emission groups in a well. to emit waves at different locations; along the first well and the reception   by receiving units along the second well.