An apparatus for autonomous downhole logging and wireless signal transport and a method for gathering well data

The invention concerns a system for autonomous, downhole logging of well data and wireless transport of the well data out of a fluid well, and also for reading off the gathered well data. More particularly, this is carried out by virtue of an apparatus being energy self-sufficient and being arranged so as to be able to register, at predefined points in time, well data in a data storage unit, which is subsequently entrained in a fluid flow out of the well, and whereing the data are read off as the data storage unit passes a well data reader located upsteam of the well's safety valve .

The prior art within well logging and data gathering strongly depends on costly well intervention operations by employing logging equipment which is 'introduced down into the well and is connected to a surface installations by means of lengthy cables. Thereby, data pertaining to pressure, temperature and flow rate of a particular section of the well may be registered. Obviously, such data only provide information about the state of the well during said intervention, an intervention which may have an interfering effect on the producability of the well. Due to the costs and complexity of

such operations, they are not carried out frequently. In 2005, an average of 0.4 well interventions per year was implemented in an investigated group of wells. To the operator it would have been desireable to gather well data at a much shorter frequency, but this is not justifiable at the costs associated with today's techniques.

Attempts have been made with respect to disposing logging sensors down within the well. Due to the vulnerability of the lengthy signal cable connections, continuous data gathering in this manner has not been successful .

The object of the invention is to remedy or to reduce at least one of the disadvantages of the prior art.

The object is achieved by virtue of features disclosed in the following description and in the subsequent claims.

The invention concerns an apparatus comprising a downhole unit without cable connection to any other components downhole or at the surface. The apparatus comprises means arranged so as to be able to generate electric energy by means of the well fluid flowing past the apparatus. Moreover, the apparatus comprises sensors which gather relevant well data and recording these into a data storage unit . An integrated system arranged to release a particular data storage unit into the well fluid flow ensures that the data storage unit is released, at a predetermined point in time, into the passing fluid, which thus transports the data storage unit out of the well. For example, the data storage unit may be read off by a reader unit positioned at a location upstream of a well head as the data storage unit passes the reader unit.

Typically, the data storage unit is a passive read-/storage memory device.

One or several apparatuses according to the invention may be used in the same well for gathering logging data from different regions of the well.

The apparatus will be operational once installed, and the apparatus then delivers a data storage unit with prescribed logging data at fixed points in time without intervention of the well being required for each logging operation.

More particularly, in a first aspect the invention concerns an apparatus for autonomous, downhole logging of well data and wireless transport of the well data out of a fluid well, the apparatus being provided with at least one sensor arranged for registration of one or several types of relevant well data, characterized in that the apparatus comprises: means arranged so as to be able to transmit the well data from the at least one sensor to at least one data storage unit, and also means arranged to release the at least one data storage unit into a fluid flow in the fluid well.

Preferably, the apparatus comprises a control unit, the control unit advantageously including a microprocessor. Advantageously, the control unit also comprises a timer arranged to bring about interval-controlled gathering of well data, and also to bring about release of a previously determined data storage unit from the apparatus .

Preferably, the apparatus comprises an electric generator and an energy storage unit. Advantageously, the energy storage unit is an electric accumulator.

Preferably, the apparatus comprises means arranged so as to be able to fix the at least one data storage unit in the apparatus, and also means arranged so as to be able to fix the apparatus in the fluid well.

Advantageously, the apparatus is arranged so as to be able to form a portion of the fluid flow conduit of a production tubing in the fluid well .

Preferably, the electric generator is an impeller disposed in a manner allowing it to be rotated by the well fluid flow.

Preferably, the impeller is connected to an induction coil.

Advantageously, the impeller is provided with a plurality of impeller blades, each of which is rotatably supported about an axis substantially coinciding with the periphery of the impeller, and being arranged in a manner allowing it to be rotated, from a substantially radial position, in a countercurrent , outward direction toward the periphery of the central conduit of the apparatus and onwards to a substantially axially directed position, thereby being able to provide a substantially circular passage throught the apparatus .

Preferably, the at least one sensor comprises means arranged so as to be able to register at least one of pressure, temperature and fluid flow rate.

Advantageously, the impeller is arranged for registration of the fluid flow rate.

Preferably, the data storage unit exhibits positive buoyancy in the well fluid.

In a second aspect, the invention concerns a system for autonomous, downhole logging of well data and wireless transport of the well data out of a fluid well, and also for reading off the gathered well data, characaterized in that the system comprises: an apparatus as described above; and

a well data reader provided at a location upstream of a well head; the well data reader being connected, in a signal- communicating manner, to a drilling- or production control unit .

Advantageously, the well data reader is arranged for remote reading of the data storage unit .

In a third aspect, the invention concerns method for gathering well data, characaterized in that the method comprises the following steps: a) connecting a system of the type described above to a fluid well; b) introducing a well fluid flow through the apparatus; c) registering relevant well data through use of sensors; d) transmitting the well data to the data storage unit; e) releasing the data storage unit from the apparatus for co-current movement out of the fluid well; f) reading off the well data from the data storage unit by means of the well data reader; and g) repeating steps a) -f) at a previously determined interval length.

An example of a preferred embodiment is described in the following and is depicted in the accompanying drawings, in which:

Fig. 1 shows a schematic cross-section through parts of a well provided with a system according to the invention;

Fig. 2 shows, in larger scale, a cross-section through an apparatus according to the invention;

Fig. 3 illustrates transmission of information from a sensor to the data storage units;

Fig. 4 shows a data storage unit released from the apparatus as it flows along in the fluid flow passing through the apparatus;

Fig. 5a shows a perspective sketch of the apparatus with the impeller blades placed in a normal, radial position;

Fig. 5b shows the impeller blades swung out toward the periphery of the apparatus for throughput of a downhole tool;

Fig. 6 shows the apparatus having the impeller removed for the sake of clarity so as to better depict a common sensor placement;

Fig. 7a shows, in larger scale, a portion of the apparatus within which the data storage units are stored in annuli outside of rotatable sleeves; and

Fig. 7b shows, in larger scale, a portion of the apparatus within which also the rotatable sleeves have been removed for the sake of clarity so as to be able to better depict the compartments within which the data storage units are stored.

Reference is first made to figure 1 in which a well 1 is formed in a subsurface structure 2 , a borehole 3 extending from a ground surface 4 at which a safety valve 5 is placed. An apparatus 11 according to the invention is disposed in the borehole 3 in a region suitable for representative measurements of well data. The apparatus 11 comprises a series of data storage units 51, threee of which are shown

released from the apparatus 11 and floating along with a fluid flow 6 through the borehole 3 and out of the well 1. A well data reader 41 is disposed near a transport pipe 7 extending above the ground surface 4 for further transport of the fluid flow 6 onward to a processing plant (not shown) for treatment, storage and transport. The apparatus 11; the well data reader 41; and the data storage units 51 with associated means (not shown) for data transmission to devices known per se for data storage and -analysis, comprise a system according to the invention.

Hereinafter, reference is made primarily to figures 2-7b, which show the apparatus 11 in greater detail.

The borehole 3 is defined against the subsurface structure 2 in a manner known per se, and by virtue of a casing 3a. The apparatus 11 according to the invention is disposed as a unit integrated within a production tubing 3b disposed in the borehole 3 in a manner known per se. An apparatus housing 12 is joined together with other section of the production tubing 3b in a manner known per se, for example pipe sections, sand screens, etc.

The apparatus 11 is formed as a lengthy sleeve with a through-going central conduit. The apparatus 11 comprises several chip-storage sections 13, each of which is arranged to house several data storage units 51 (chips) . A sleeve- shaped chip housing 14 is provided with a series of recesses 15 in the internal wall of the chip housing 14. A cover sleeve 16 is disposed internally within the chip housing 14 and spans substantially the entire length of the chip housing 14. The cover sleeve 16 is provided with a port 17 which is complementary to the recesses 15 of the chip housing 14 in such a way that, when the cover sleeve 16 is rotated to a particular position relative to the chip housing 14, a data

storage unit 51 may be released from the chip-storage section 13 so as to be entrained by the fluid flow 6 conveyed through the apparatus 11. Each cover sleeve 16 is provided with a rotary coupling 18, see fig. 7a, which allows the cover sleeves 16 of all chip-storage sections 13 to be rotated in a synchronized and sequential manner, whereby controlled rotation of a drive sleeve 22 results in a particular data storage unit 51 being released from the apparatus 11 by virtue of the port 17 of a particular chip-storage section 13 being aligned in a desired position.

The drive sleeve 22 is disposed within a control section 21 arranged adjacent to an end of the series of chip-storage sections 13. A drive arrangement (not shown) is connected to the drive sleeve 22 and is controlled by a control unit 23. The control unit 23 comprises means for signal communication with the sensors 24 and the data storage units 51. The control unit 23 also comprises an accumulator (not shown) for electric energy provided from a generator section 31. The control section 21 is sleeve-shaped.

Also the generator section 31 is sleeve-shaped and is arranged adjacent to an end of the control section 21. An impeller 32 comprises a peripheral support ring 33 rotatably supported in a generator housing 34. A series of impeller blades 35 are disposed radially and directed toward the central axis of the generator housing 34. Each impeller blade 35 is rotatably supported in the support ring 33 in a manner allowing them to be rotated away from a radially directed position and against the normal flow direction of the fluid flow 6 in the well 1. A stopper (not shown) prevents the impeller blades 35 from rotating in a co-current direction and away from their radially directed positions. When rotating, the impeller 32 is arranged to induce electricity

in an electric circuit (not shown) connected to a charging circuit (not shown) for the accumulator of the control unit 23.

When the system according to the invention is to be connected to the well 1 to be logged, first the control unit 23 of the apparatus 11 must be programmed for logging and release of a data storage unit 51 with the desired well logging data at a prescribed interval size, for example registration of well data every Monday during the period of 12.00-12.05 hrs . GMT, and subsequent release of a particular data storage unit 51. Preparation of the apparatus 11 also comprises setting of the drive arrangement (not shown) , cover sleeves 14 and the program for controlling the drive arrangement in a manner whereby the data storage units 51 are released in a desired order. The apparatus 11 is charged with the required number of data storage units 51.

The well data reader 41 is installed near the transport pipe 7 at a location upstream of the safety valve 5.

One or several prepared apparatuses 11 are connected together with other downhole equipment known per se into a complete production string and are introduced down into the well 1.

When the production starts, the fluid flow 6 will put the impeller 32 into rotation, and the accumulator of the control unit 23 is charged with electric energy. The energy is used for operation of the control unit 23 and the drive unit (not shown) . At a predefined point in time, the control unit 23 is activated so as to gather well data from the sensor (s) 24 and store the data in the data storage units 51. The storage may take place by virtue of all data storage units 51 receiving the same information, and previously received information may possibly be overwritten. When arranged in this manner, the

order of releasing the data storage units 51 is of no importance .

A chip is released at a particular time by virtue of the drive arrangement (not shown) is set into a controlled motion whereby the drive ring 22 rotates the cover sleeves 16. The rotary couplings 18 are arranged in a manner allowing the cover sleeve 16 closest to the drive ring 22 to be directly rotated by the drive ring 22, whereas the following cover sleeve 16 is first engaged when the first cover sleeve 16 has rotated nearly a full revolution. The subsequent cover sleeves operate in the same manner. By so doing, one after one recess 15 is uncovered, and the chip storage sections 13 are emptied successively from the one being closest to the drive section 21 to the one being furthest away therefrom.

The released data storage chip 51 is entrained in the fluid flow 6 out of the well 1. As the data storage chip 51 passes the well data reader 41, the well data are read and transmitted to the associated means (not shown) for data transmission to the devices known per se for data storage and -analysis. The data read-off from the data storage unit 51 takes place in a manner known per se by virtue of wireless transmission .

It is obvious that the rotation speed of the impeller 32 may be used as a basis for calculation of the flow rate through the apparatus 11.

When a downhole tool is required to be introduced through the apparatus 11, the blades 35 of the impeller 32 will be swung out toward the periphery of the central conduit of the apparatus when experiencing pressure in a countercurrent direction, thereby allowing the downhole tool to pass unobstructedly. To a person skilled in the area, it is

obvious that during such an operation, the impeller 32 must be inoperative due to, for example, the fluid flow 6 having discontinued. Moreover, the impeller blades 35 must be kept in a swung-out, axial position, at least during the operation of pulling out the downhole tool from the well, by means of a tool (not shown) suitable for the purpose, for example a sleeve, which may have been conveyed down to the apparatus 11 by means of said downhole tool .

It may be possible to dispose one or several apparatuses 11 according to the present invention in the well in one operation and simultaneously introducing a production tubing string down into the well. When the apparatus 11 is disposed, it is energy self-sufficient and is controlled by the program installed in the control unit 23, and no form of cable connection to the surface is therefore required. The well 1 is logged at predetermined points in time, and the stored data are transported along with the fluid flow to the surface by virtue of data storage units 51 being released from the apparatus 11. Having the capacity of storing a large number of data storage units 51 in the apparatus 11, it will be possible to carry out well logging at short intervals, for example at intervals of a week, without having to implement a well intervention other than when all data storage units 51 have been sent out of the well. Depending on the capacity of the apparatus 11 and the size of the logging intervals, it is possible to carry out logging over a period of up to several years without having to implement a well intervention.