In the production of oil and gas, oil/gas is lead to the surface through so-called tubing in a well. At the surface, at the upper end of the tubing, comprehensive valving and safety equipment are arranged thereto.

Somewhat away from its lower end, the tubing has a seal arranged thereto, the so-called packer, which is ar- ranged to seal between the tubing and the wall of the well, which is normally lined with a steel tube also called casing, so that oil or gas cannot enter the an- nulus outside the tubing. Between said packer and the lower end of the well, the casing is perforated, so that oil or gas may flow into the well, further up into the tubing and to the surface. In the annulus outside the casing and between the packer and the lower end of the casing, a filter, for example a gravel pack, may be provided, which is to prevent sand from the reservoir from being carried by the gas or oil flow.

The lower end of the casing which is in the productive zone of the well, i. e. the part of the casing located between the packer and the bottom of the well, is of particular interest and calls for attention for several reasons. It is desirable to be able to decide which part of the reservoir to produce from. This is decided partly by positioning the perforations in the right area of the casing. It is topical to carry out perfora- tion in several turns to exploit the reservoir, zone by zone, in the course of time. There may also be drilled extensions from the lower part of the casing out into the reservoir. It is further known to install zone de- fining packers in the annulus between the casing and the wall of the well. By installing plugs and chokes, maybe choke valves, within the lower part of the cas- ing, the production from the reservoir may be con- trolled, so that the reservoir is drained in the opti- mal manner.

To monitor the production and ensure optimal condi- tions, it is known to arrange downhole sensors to ob- serve pressure, temperature, water content in the oil/gas, detect sand and other items. The sensors should be placed in the productive part of the well, i. e. between the packer and the bottom of the well.

Sensor signals are transferred to the surface through lines running in the annulus outside the tubing. The sensors are installed at the same time as the tubing, and the lines are secured to the exterior of the tub- ing. Possible actuators for downhole valves are ener- gised by lines from the surface and are controlled from the surface, either by controlling the energy supply or through particular control signals. Both electric and hydraulic lines may be of interest.

Deposits occur in the tubing, particularly in the lower part of the tubing. In connection with well maintenance it is of current interest to perform mechanical clean- ing inside the tubing. Sensors, actuators, chokes and other equipment must either be arranged to bear and give room for such cleaning, or the equipment must be removed before cleaning is started.

The packer is of great importance in terms of safety, and quite naturally there are strict requirements to the packer itself and to the setting of it. The packer may not be removed, unless other satisfactory security is provided.

When equipment, to be connected to lines from the sur- face, is placed closer to the well bottom than the packer, problems arise in passing the lines past the packer. The lines may be taken through the packer it- self, but this requires particular measures. The lines may be taken through the tubing wall further away from the end of the tubing than where the packer is, and back out, nearer the end of the tubing. The lines will then run inside the tubing a short distance, and will then be highly exposed. Therefore, it is a better solu- tion to pass the lines past the packer in channels in the tube wall itself. Still, a sealing problem will arise, as oil and gas may then enter the annulus be- tween the packer and the surface. Sensors and other equipment, to be connected to lines and placed closer to the well bottom than the packer, must be installed at the same time as the tubing. Maintenance of such equipment often involves that the tubing must be ex- tracted from the well, which is, of course, both com- plex and expensive.

A superior object of the invention is, therefore, to simplify the maintenance and use of equipment in an area between the packer and the well bottom. In par- ticular it is an object to simplify installation and maintenance of equipment which is to be connected to lines in said area.

The aims are reached through features as defined in the following description and subsequent claims.

According to the invention, the well is provided with a tubing which in a known manner has a packer arranged thereto. A telescopic extension of the tubing is ar- ranged to permit connection to a holder inside the tub- ing, so that the telescopic part projects from the lower end of the tubing. The telescopic part may be re- leased from the holder and be extracted from the well for maintenance. Sensors, chokes, valves and actuators and other equipment may be mounted in the telescopic part before the latter is run into the well.

According to the invention, lines belonging to said sensors and actuators are terminated in a part of a coupling which is arranged to co-operate with a comple- mentary connection part in the tubing. The lines may with advantage be passed in particular channels in the body material of the telescopic part.

Said complementary connection part is arranged to the tubing further from the well bottom than where the packer is. The complementary connection part is con- nected to lines which are passed, in a known manner, in the annulus outside the tubing to equipment on the sur- face.

When the telescopic part is inserted into the well and secured to the holder in the tubing, said connection establishes communication between the sensors and the actuators.

The invention will be described in the following by means of a non-limiting example of an embodiment with reference to the accompanying drawings, which show a simplified side view of part of a vertical well with tubing provided with a lower telescopic part.

In the figure reference numeral 1 defines a well, in which a tubing 2 is arranged in a manner known in it- self. The well 1 is shown having a casing 3 which is fixed through cementation and is perforated in its lower part. A packer 4 is in an ordinary manner set be- tween the tubing 2 and the casing 3.

In the tubing 2 is interposed a holder 5 carrying a telescopic part 6 which projects from the lower part of the tubing 2. The telescopic part 6 is stepped and rests on a shoulder 7 of the holder 5. Further, the telescopic part 6 is provided, in a manner known in it- self, with grippers 8 which are arranged to allow ra- dial displacement thereof to engage an annular groove 9 in the holder 5 and thereby lock the telescopic part to the holder 5. The grippers 8 are arranged so that they can be triggered to release the telescopic part 6 from the holder 5 by means of a tool 10, which is arranged to be releasably connected to the upper end of the telescopic part 6.

The tool 10 is provided with a set of external locking pins 11 which are arranged to engage an internal lock- ing groove at the upper end of the telescopic part 6.

The grippers 8 and the locking pins 11 with complemen- tary recesses 9,12 may, with advantage, be made in ac- cordance with known principles, which are used for grippers and locking pins of known equipment and tools.

In the holder 5 is provided a first part 13 of an in- ductive coupling which is arranged to be able to co- operate with a second part 14 of said inductive cou- pling. The first part 13 of the inductive coupling 13, 14 has a first set of electric conductors 15 arranged thereto, for transferring energy and electric signals between the first part 13 of the inductive coupling 13, 14 and not shown equipment on the surface. The second part 14 of the inductive coupling 13,14 is electri- cally connected to a sensor 17 and an actuator 18, which has an adjustable choke valve 19 in the tele- scopic part 6, by means of a second set of electric conductors 16. Electric signals are transferred between the sensor 17 and the actuator 18 via the electric con- ductors 15,16 and the inductive coupling 13,14.

Conductive, electric couplings may also be provided, for example through plugable electric connectors in the bearing surface by the shoulder 7. Instead of, or in addition to, said electric connectors, a person skilled in the art may easily arrange hydraulic connections for the transfer of hydraulic energy and hydraulic signals between the holder 5 and the telescopic part 6. The first set of electric and/or hydraulic lines 15 may in a known manner be passed in the annulus outside the tubing 2 and above the packer 4. The second set of lines 16 may, with advantage, be passed in not shown channels in the body material of the telescopic part 6.

Seals 20,21 define a zone in an annulus 22 below the end of the tubing 2 and outside the telescopic part 6, which is shown to be sealed at its lower end. A set of ports 23 in the telescopic part 6 is arranged to direct oil or gas from the defined zone of the annulus 22 into the telescopic part 6 below the choke valve 19, as the well 1 is provided with perforations 24. Production of oil/gas may be controlled from the surface by remote control of the choke 19 based on signals from the sen- sor 17. As required, more sensors, more valves, more zone-defining seals and more sets of ports may be pro- vided in the telescopic part 6.

Whenever there is a need for maintenance of the tele- scopic part 6 or of equipment provided in the tele- scopic part 6, the tool 10 is inserted into the well 1 and connected to the upper end of the telescopic part 6, so that the locking pins 11 engage the locking re- cess 12. Thereby the grippers 8 are passed out of the groove 9 of the holder 5, and the telescopic part 6 may be pulled up and out of the well 1, hanging from the tool 10. When the telescopic part 6 is ready for use, it is lowered into the well 1, hanging from the tool 10, until the telescopic part 6 lands on the shoulder 7 of the holder 5. The locking pins 11 are released so that the tool 10 may be pulled up and out from the telescopic part 6. Thus, the grippers 8 are activated to engage the groove 9, so that the telescopic part 6 is locked to the holder 5.