INJECTOR FOR INJECTING A TRACER INTO AN OIL OR GAS RESERVOIR

Abstract: Injector (1) for injecting a traceable material into an oil and/or gas reservoir, the injector being lowered down in a bore hole that is in communication with the reservoir, followed by activating an electro-hydraulic system to inject a traceable material stored in a container into the reservoir. The injector is provided with a gland plate (7) that seals the space between the injector and the wall of the bore hole (16) in a manner that pevents traceable material to be distributed in the bore hole, but secures direct injection of the material into the reservoir. The injector is adapted to be positioned at a specific depth level in the bore hole, and to be cleaned by pressurised liquid after the injection operation is fulfilled.

Description: Injector for injecting a tracer into an oil or gas reservoir This invention relates to an injector for injecting a traceable material or a tracer into a bore hole that is connected to an oil- and/or gas reservoir. When a promising reservoir of oil and/or gas is discovered, the following procedure is to determine the size and shape of the reservoir. Then the field is divided into a number of geometrical squares, followed by performing a drilling operation to obtain bore holes in the squares. In some of the bore holes there are placed injectors according to a certain pattern, and at various depths. A traceable material is then injected from the injectors into the oil- and/or gas reservoir followed by measuring the amount of distribution of tracer or tracer elements. This measurement is performed by the provision of an amount of detectors placed in near and distant located bore holes according to a pre-calculated geometrical pattern. The tracer injections may be repeated after a certain time, at intervals in dependence of the content of the reservoir, the permeability, the temperature and pressure, and finally the properties of the traceable material. Two different arrangements for injecting a traceable material in an oil and/or gas reservoir have been known for a long time. One arrangement comprises the provision of an explosive charge in relation to a piston in the injector. The charge may for instance be detonated by the means of a timer, whereby the piston compresses a container for traceable material, followed by the injection of the content into the reservoir. The other arrangement, e.g. as described in US patent no. 4.220.264, comprises a hydraulic system with a piston, manually actuated by the provisions of a valve/spring device that compress a container of traceable material followed by the injection of traceable material into the reservoir. Meanwhile, the above mentioned arrangements are encumbered with considerable disadvantages. One disadvantage that occurs when using a timer, or when the depth level is indicated by measuring the wire length that is paid out, is that the calculated depth level may be encumbered with considerable calculation errors since the lowering speed may vary caused by speed variations in the winch motor, strain in the wire, and finally the lowering operation itself may be disturbed by faults. Further, it is difficult to estimate the most favourable charge for a satisfactory distribution of the traceable material. An other disadvantage by injection of the traceable material into the reservoir, is that the annulus defined between the injector and the wall in the bore hole will not be sealed. As a result of this, the precise depth level of injection may not be exactly determined because the traceable material is allowed to distribute lengthways in the bore hole before entering the reservoir. Consequently, the calculations of such reservoir parameters as amount of oil and gas, depths and dissemination will be encumbered with statistical uncertainty. A further disadvantage is that in a period of time, tracer material will accumulate in and upon the injector. When applying a radioactive material, for instance cesium, repeatedly handling of the injector may cause health injuries to the operators. It is therefore important that the injector has provisions to be cleaned after the injection, and that the depth level of the bore hole may be exactly determined to measure the distribution of the tracer, and accordingly the character of the reservoir can be calculated very precisely. By the present invention it has been developed an injector for injecting a traceable material in an oil- and/or gas reservoir that is substantially improved in comparison with the known injector arrangements. The injector according to the invention is reliable in operation, easy to operate and precise in use. Further, the injector has favourable production and operation costs, and is safe as to the health of the operators. According to the present invention, the above mentioned advantages are achieved by an injector as described in the introduction, the injector is characterized in that the traceable material is injected into the reservoir through a gland plate or the like, where the plate is arranged to be stored in a retracted position in the injector when lowering down or pulling up the injector, and is arranged to be pressed into abutment with the wall in the bore hole when performing the injection operation. The accompanying dependent claims 2-11 defines advantageous features of the invention. One way of carrying out the invention is described below with reference to drawings that illustrate one specific embodiment in which: Fig. 1 shows a flowsheet of the main components which is included in the invention Fig. 2 illustrates schematically an injector according to the invention Fig. 3 is a longitudinal section of the injector in Fig. 2, on an enlarged scale and divided into numbered sections Fig. 4a),b),c) shows on a further enlarged scale a pantograph mechanism that is a part of the invention and shown in Fig. 2 and Fig. 3 Fig. 5 is an alternative embodiment of the hydraulic system as shown in Fig. 1. Fig. 1 shows the principle by which the injector is constituted. The injector is shaped as an relatively long and cylindrical or approximately cylindrical object, and will also be seen in Fig. 2, 3 and 4. A computer that controls a control panel (not shown) may be placed on the earth surface or on board at a surface vessel, the computer comprises among other things a data recording module and a calculation-. control module. These modules are connected with electrotechnical components in the injector by a combined element consisting of a hoisting wire and a current carrying cable 17. The recording module in the control panel receives a number of data concerning pressure, depth and temperature at different depth levels in the bore hole via sensors (not shown) arranged in the injector. Calculations are performed in the calculation module and then control signals at a certain sequence will be transmitted to the electrotechnical components in the injector via the current carrying cable. The data will be stored in situ, but in addition data will be stored in a database with a high memory capacity. This database may have a distant location, possibly on shore. The injector 1 is preferably provided with three hydraulic or fluid systems, as shown in Fig. 1 , where: 1. The first system comprises a gland plate 7, arranged to be brought into abutment with the wall of the bore hole by the means of lever arms/pantograph 6. The lever arms/pantograph is operated by a piston rod 18 forming a part of a piston/cylinder device 5, 25 , where the latter by means of lines or bores 19 and 20 is connected to a slide valve controlled by an electric motor 21. Further, the system comprises a piston pump 4 driven by a electric motor 3 in such a manner that pressurised well fluid is transported to the cylinder 5 via the slide valve 2 and the connections 19 and 20. The fluid transported to the cylinder 5 will be led to the one side of the piston 25 or the other, depending on the position of the slide valve 2. When the piston 25 is in the position as shown in Fig. 3 section 10, the pantograph 6 and the gland plate 7 are in a retracted position in the injector. 2. The second system comprises a piston pump 14 and a slide valve 13 operated by an electric motor 15 in such a manner that traceable material contained in a chamber 9 is injected under pressure into the reservoir via a connection 22, the pantograph 6 and the gland plate 7. 3. The third system consists of a liquid chamber 11 , a piston 28 and a gas chamber 12 actuated by means of a valve 10. The piston 28 is forcing the liquid, preferably a brine, under high pressure out of the chamber 11 , to clean the chamber 9, the connection 22, pantograph 6 and the gland plate 7. When the injector is lowered down to a specific depth level in the bore hole, the electric motor 21 is adapted to place the slide valve in a position allowing well fluid to flow to the cylinder 5 via the connection 20. The electric motor 3 is then put into operation to drive the piston pump 4 which supplies well fluid to the cylinder 5 via connection 20. The well fluid is thereby pressurised to move the pantograph and the gland plate outwardly relative to the injector by means of piston rod 18 connected to piston 25. Said elements are moved outwardly until the gland plate is brought into abutment with the wall of the well (see Fig. 2), to obtain a sealed communication between the injector and the reservoir. The electric motor 15 is adapted to rearrange the slide valve 13 allowing fluid to flow to the piston pump 14. The piston pump 14 delivers high pressurised well fluid to a trace material container located in chamber 9, whereby the content being forced out of the container, through connection 22, the pantograph 6, gland plate 7 and finally into the reservoir. After the traceable material has been injected into the reservoir, the slide valve 2 is rearranged by provision of the electric motor 21 to allow the piston pump to force well fluid through the connection 19 to replace the piston 25, the pantograph 6 and the gland plate back to the initial position as shown in Fig. 3 sections 4 to 10. As the well fluid is forced back through connection 19, the pressure in cylinder 5 rises immediately and distributes through the connection 23 reaching a ramification device that is connected to a valve 10. Valve 10 is adapted to be opened and to release the propellant gas in gas chamber 12 to let the liquid in chamber 11 being forced out through trace chamber 9, connection 22, pantograph 6 and gland plate 7, and thereby cleaning said elements. Fig. 2 shows schematically the injector lowered down into a bore hole, the pantograph 6 being in an extracted position with the gland plate 7 brought into abutment with the wall of the bore hole, the injector being ready for injecting a tracer into the reservoir. In Fig. 3, a longitudinal section of the injector is shown, where the injector is divided into sections 1 to 31 for the sake of clarity. At the one end of the injector, i.e. in the sections 26 to 31 , there are located electrotechnical components such as actuators and sensors (not shown) forming a part of the operation- and control systems. These components will not be further described since they do not represent a part of the invention as it is defined in the claims. The sections 16 to 20 comprise electric motors 21 and 3 adapted to control the slide valve 2 and to drive the piston pump 4 respectively, to provide transport of well fluid to cylinder 5 via connections 19 and 20. This arrangement is similar to the hydraulic circuit described previously. The sections 22 to 25 comprise electric motor 15 that controls the slide valve 13 and drives the piston pump 14 for transport of tracer into the reservoir, similar to the hydraulic circuit 2 as described above. The sections 12 and 13 show the valve 10 adapted to be opened at a certain pressure to initiate the release of gas contained in chamber 12, and thereby forcing out fluid contained in chamber 11 to perform a cleaning operation of tracer chamber 9, connection 22, pantograph 6 and gland plate 7. This arrangement is similar to the hydraulic system 3 as previously described. The trace chamber 9 with the trace container (shown schematically), is shown in Fig. 3, section 1 to 3. Fig. 4a) shows on an further enlarged scale the lever arms/pantograph 6 with the gland plate 7 in an extracted position, i.e. the gland plate 7 being forced into abutment with the well wall 16. The lever arms 26 are hinged to a supporting structure 27 of the gland plate 7 by a pivotal connection. Further, the supporting structure 27 is connected to the piston 25 in cylinder 5 by means of piston rod 18 and pivotal connections. The tracer is transported from the tracer chamber 9 via the connection 2 in the injector wall, and further via a tube or hose 24 through a bore 29 in the gland plate 7. As shown in Fig 4b) and c), the gland plate is adapted to fit the wall in the bore hole (well casing), and is provided with a packing 30 to obtain a tight connection when being in abutment with the wall. As will be seen in Fig. 4c, the gland plate is connected to the lever arms 26 by a two-way pivot bearing 37. The purpose of this bearing arrangement is to provide a correct alignment of the gland plate 7, to obtain a tight abutment with the well wall 16. It will further be seen in Fig. 4b) and c) that the gland plate is equipped with one or more lugs or projections adapted to come into engagement with holes/perforations or beads formed in the well wall 16. The injector may be provided with cantilevered rolls 39 or wheels arranged at the gland plate and at the injector body respectively, rendering it possible to rotate the injector, for instance when searching for openings in the well wall. Fig. 5 shows an alternative embodiment of the hydraulic systems as shown in Fig. 1 and as described previously. As a replacement of the hydraulic system 3 with a separate chamber 11 containing a brine for pressure cleaning of the trace chamber 9, both the injection and cleaning operations may be performed by the hydraulic system 2, where the system in addition comprises means for pre-injection of well fluid before injecting the tracer. The pre-injection is, as mentioned previously, desirable to determine whether the gland plate 7 is in contact with the reservoir or not. The pre-injection system comprises bores/pipes 31, a slide valve 32 actuated by a motor 33 and finally a pump 14. The system is activated when the valve 32 is moved to obtain a connection between the pump 14 and the conduit 31 that is in communication with the gland plate 7. After the pre-injection operation is fulfilled, i. e. after a communication with the reservoir is achieved, the slide valve is rearranged to be prepared for injection of the tracer as described in the explanations to Fig. 1. Fig. 5 shows in addition a safety device for releasing the gland plate 7 when a failure in the hydraulic system 1 or control system for the injector possibly occurs. In communication with the bore/pipe connection 20 there is arranged a pressure accumulator 34, a return spring 35 and finally drainage holes 36. Should any failure as mentioned above occur, drainage hole 36 will provide a bleeding of the hydraulic system 1 and a pressure drop in the same, allowing the spring to retract the gland plate 7 to a retracted position in the injector. The lever arms 6 that are hinged to the injector, at an inclined angle to the length axis of the same, effect a withdrawal of the gland plate relative to the well wall, when pulling the injector cable 17.

Claims: Claims 1. Injector for injecting a traceable material into a bore hole in communication with an oil- and/or gas reservoir, the injector being provided with a container (9) or the like for the traceable material and means for injecting said material, characterized i n that the traceable material being injected into the reservoir via a gland plate (7) or the like arranged to be located in a retracted position in the injector when lowering down and pulling up the injector in the bore hole, the gland plate further having provisions to be moved into tight abutment with the wall of the bore hole (16) when performing the injection operation. 2. Injector according to claim 1 , characterized in that the gland plate (7) is supported by means of an pantograph or lever arms (6), and may be moved by the latter. 3. Injector according to claim 2, characterized in that the gland plate (7) is connected to the pantograph/lever arms (6) by the provision of an two-way pivot bearing. 4. Injector according to claim 1 , characterized in that the gland plate is provided with one or more lugs or projections (3) adapted to come into engagement with holes or beads in the wall of the well. 5. Injector according to claim 1-4, characterized in that the injector is provided with cantilevered rolls or wheels (39) arranged at the gland plate (7) and at the injector body (1) respectively. 6. Injector according to claim 2-5, characterized in that the pantograph or lever arms (6) are moved by means of a piston-Zcylinder device via a piston rod (18). 7. Injector according to claim 1-6, characterized in that the piston-Zcylinder device (5) is actuated by well fluid contained in a first hydraulic system, said system comprises a pump (4) driven by an electric motor (3), and a slide valve (2) controlled by an another electric motor (21). 8. Injector according to claim 1 , characterized in that the injection of traceable material is effected by forcing well fluid through the container for the traceable material (9), and comprises a second hydraulic system with a pump (14) operated by an electric motor (15). 9. Injector according to claim 1, characterized in that the chamber for the traceable material (9) and the gland plate (7) including its pipe connections and bores (2) may be cleaned by pressurised injection fluid from the well by the provision of a pump (14) operated by an electric motor (15). 10. Injector according to claim 1 , characterized in that the chamber (9) for the traceable material and the gland plate (7) with its pipe connections and bores (22) may be cleaned by a pressurised fluid contained in a container (11) forming a part of a third hydraulic- or liquid system. 11. Injector according to claim 10, characterized in that the pressure in the third hydraulic system is achieved by means of a pressurised gas stored in a pressure container or chamber (12), said container or chamber (12) being in connection with the liquid container (11).

Inventors: BOEE EINAR, CARLSEN HANS PAUL, HAUGERUD OLAV SVEINUNG, HOLGERSEN STIG, BOEE, EINAR, CARLSEN, HANS, PAUL, HAUGERUD, OLAV, SVEINUNG, HOLGERSEN, STIG
Applicants: BOEE EINAR, CARLSEN HANS PAUL, HAUGERUD OLAV SVEINUNG, HOLGERSEN STIG, NORSK HYDRO AS, BOEE, EINAR, CARLSEN, HANS, PAUL, HAUGERUD, OLAV, SVEINUNG, HOLGERSEN, STIG, NORSK HYDRO A.S
Application year: 1995
Main classification: E21B33
IPC codes: E21B27, E21B33