WO1998012417A1

WO1998012417A1 - Monitoring device and method

Info

Publication number: WO1998012417A1
Application number: PCT/GB1997/002497
Authority: WO
Inventors: George Albert Brown
Original assignee: BP Exploration Operating Co Ltd
Current assignee: BP Exploration Operating Co Ltd
Priority date: 1996-09-19
Filing date: 1997-09-12
Publication date: 1998-03-26
Anticipated expiration: 1999-03-19
Also published as: GB9619551D0; AU4215697A

Abstract

An oil/gas reservoir completion pipe (1) is provided with at least one external sensor, e.g. 2-6 sensors, such as a resistivity electrode (6) or a pressure (7) or temperature sensor (9), at least one of which is preferably external to the pipe supported by means of strapping, or a releasable or non-releasable framework or housing externally mounted on the pipe. A method of determining one or more formation parameters, e.g. resistivity, pressure and temperature down hole e.g. in a reservoir to provide information on conditions therein may be carried out on a continuous basis during production by passing said completion pipe into the reservoir and measuring the parameter. Parameters may also be measured during withdrawal of oil and/or gas from the reservoir.

Description

MONITORING DEVICE AND METHOD

The present invention relates to a monitoring device and method of monitoring, in particular for use in oil and/or gas wells

It is desirable to know what is happening down an oil and/or gas well during production, and to this end it is known to stop production, run a sensor on the end of a wire line down hole to the reservoir, take measurements, withdraw the sensor and restart the production Because of the loss of production this entails, many such reservoir logging operations take place very infrequently e g once every 1-2 years But by this time any problems may be insurmountable Use of coiled tubing does enable the logging to be performed without stopping production, but it is still a discontinuous operation Finally all such periodic approaches need a top hole πg, which is very expensive for deep sea wells

A monitoring device is now provided enabling measurement of one or more parameters on a continuous basis during production to provide information on the conditions down hole, e g m the reservoir The present invention provides a reservoir completion pipe provided with at least one external sensor

The present invention also provides a pipe stnng comprising said completion pipe carrying the sensor and at least one section of completion tube attached to said pipe The present invention also provides a method of determining a parameter in a reservoir, which comprises passing down a hole into a reservoir a sensor, and measuring said parameter characterized by passing a reservoir completion pipe provided with at least one sensor into the reservoir and measuring said parameter In another embodiment there is provided a method of producing oil or gas from a subterranean reservoir via a well, which comprises passing a plurality of

I sections of production and reservoir completion pipe down said well into said reservoir and withdrawing oil and/or gas therefrom characterized in that at least one section of reservoir completion pipe is provided with at least one external sensor, said section of pipe is passed into the well into the reservoir, and during withdrawal of oil and/or gas the sensor measures one or more reservoir parameters

The reservoir completion pipe which is provided with the sensor may have any convenient internal and external diameter e.g. 2-10 inch ( 5 08-25.4cm) especially 4'/2, 7 or 9^/ inch (1 1.43, 17.78 or 24.45cm) Advantageously it has the same diameter, in particular internal diameter as the sections of completion pipe to which it is attached, so the sensor-carrying-pipe constitutes no restriction to fluid flow It is usually made of steel and is of circular internal cross section It may be about the same length as a usual section of completion pipe e g about 10m, but advantageously is 0 5-5m long It usually has threaded ends, preferably one internally and one externally threaded end, for engagement with corresponding threads of neighbouring sections of production pipe In particular for use with a resistivity sensor, one or both threaded ends may carry an electrically insulating coating, e g one sprayed onto the threads; the coating may be of thermoplastics material but preferably is of thermoset resin, and may be a silicone polymer Alternatively if desired the production pipe carrying the sensor may itself be of electrically insulating material, e g engineering plastics material optionally reinforced with fibres e.g. elongate or chopped fibres such as carbon fibres

The sensor may be any conventional sensor and may measure temperature, pressure, fluid velocity, resistivity, density or relative proportions of produced fluids Examples of suitable sensors include an external or internal pressure sensor or temperature sensor, an internal ultrasonic sensor, a low energy density sensor, a venturi flowmeter, or an external resistivity electrode Suitable pressure sensors include quartz or strain gauge type sensors A suitable external resistivity electrode may be of the multi-electrode type The sensor may be mounted externally of the reservoir completion pipe It may simply be strapped onto the outside, but preferably is at least partly protected from damage within the external surface of the reservoir completion pipe or within a framework itself externally mounted on the pipe Thus the sensor may be in a slot or groove, which may be radial, circumferential or longitudinally extending The slot or groove may be in the external wall of the pipe, which wall may otherwise of substantially uniform thickness. Preferably the wall has at least one portion thicker than other portions, the thicker portion having in its external surface at least one groove or slot to receive the sensor or sensors; preferably the pipe has in transverse cross section, a pair of parallel outwardly extending external surfaces with a face to the pipe between them substantially normal to those surfaces. In the latter case the pipe may have one or more longitudinally extending grooves to receive the sensor or sensors. The sensor or sensors may also be in an open elongate framework extending outwards at least one location from the pipe, which framework may be integral with or releasably attached to the pipe. Inside the framework is located the sensor or sensors. The framework may be sufficiently open to allow radial access of the reservoir fluid to the sensor if required but may be sufficiently closed to restrict movement of, especially outward movement of, the sensor away from the pipe. The framework may thus be partly open on its outside distant from the pipe, or may be closed on that outside, though in both cases it is open from its ends to allow access of fluid to the sensor. The sensor(s) may also be in a housing mounted externally on the pipe, either releasably or preferably non- releasably e.g. by welding. The housing may have the sensor outwardly facing and contain the associated electronic mechanisms. The housing may be in the form of a sheath at least partly surrounding the pipe. The sheath may surround the pipe and be in continuous contact therewith but preferably is in contact at its ends but not internally so the sheath and pipe define a cavity for the cable and sensor terminals (see later) The sensors may be disposed symmetrically or asymmetrically in or around the periphery of the completion pipe. The external sensor(s) is used to determine at least one parameter outside the pipe i e. in the formation while any internal sensor(s) is used to determine at least one parameter inside the pipe i.e of the pipe contents. One or both types of sensor is preferably located in the pipe wall with external access e.g. located in a slot or chamber such as a radial one in the wall openable to the outside of the pipe but closed or closable therefrom for physical protection at its outer entrance by closure means e.g. a cap or screw threaded lid or grub screw; depending on the nature of the sensor, the closure means may be perforated to allow liquid access to the sensor but still protect it e g for a pressure sensor In some cases e.g. with an internal ultrasonic sensor the sensor will be located on/in the inside surface of the pipe wall The wall may be of substantially uniform thickness in an axial direction, which thickness may be higher than that of the pipes to which it is attached, though preferably with the same internal diameter. In this embodiment the sensor(s) is preferably in a chamber in the pipe wall accessible externally of the pipe.

The external form of the sensor may be a pod for insertion into the framework or an elongate body for insertion into the slot or groove. The sensor is usually sealed apart from its measuring head, except as required e.g. for measuring temperature.

The completion pipe is provided with at least one sensor e.g. as described above, and especially a resistivity sensor either alone or with at least one other sensor; there may be at least 2 different sensors, especially when one sensor is a temperature sensor. Preferably there are 2-6 sensors, especially a resistivity sensor, and one or both of a temperature and pressure sensor. When the pipe is provided with more than one sensor, at least one, preferably the resistivity sensor is external of the pipe and the rest may be internal or external of the pipe, but especially with an internal and/or external pressure and/or temperature sensor and/or sensor for measuring flow and/or the relative proportions of the production fluids.

Preferably when the overall completion pipe string through the reservoir has more than one sections of pipe provided with at least one sensor, the or each such section is provided with means for longitudinal aligning of the locations of the sensors on the pipe. By this means the sensors are all in the same side of the pipe string aiding their protection from damage and also minimising the length of cables, used to transmit measurement data from the sensors up the pipe string outside e.g. to the well head.

The sensor(s) transmits signals carrying the data to a data collecting means and hence data analysis system. The mode of transmission may be down elongate signal transmission means, such as a wire or optical fibre lines or via radio or other waves. Such lines may pass in at least one passage in the pipe wall or in the external wall surface, as in a circumferential slot. The data collecting means is usually at the surface. Preferably a signal transmission line passes from each sensor to a junction box for the sensor-carrying-completion pipe, and the junction boxes from different completion pipes are joined together e.g. by armoured cable. The cable preferably carries a return line for signals from more than one sensor of a particular type especially from all the sensors of that type; less preferred the cable may have one line for signals from each sensor The cable also contains at least one line for powering one or more sensors, and the power line passes from each junction box to each sensor. The junction box is usually mounted externally of the sensor-carrying-completion pipe, e.g. strapped on the outside but preferably in an axial groove in the pipe wall e.g. an external groove in at least one portion of the pipe wall, which may or may not be the same as any such portion in which the sensor may be located; the groove may extend substantially the full length of the sensor-carrying completion pipe with the junction box and the two cables received in it.

In use the pipe provided with the sensor is attached to a section of reservoir completion pipe, e.g. via their threaded portions In the case of more than one sensor pipe in the reservoir, the sensor pipes may be separated by 1 or more sections of reservoir completion pipe e.g. may be between each alternate liner section and hence may be at about 10m or more intervals. For vertical wells about 10m intervals are particularly useful, whereas for deviated wells with angles from the vertical of at least 45°, intervals between sections of sensor pipe of 100-500m may be used The reservoir completion pipe may already be perforated as in slotted liner pipe optionally wire wrapped, but is usually perforatable.

The devices of the invention may be installed and used as follows The well is drilled into the reservoir underground and then in the completion step, completion pipe is passed downhole. In to the sequence of pipes is attached the pipe provided with the sensor, at a location in the pipe string commensurate with its location in the desired place in the reservoir Cable e g armoured cable to transmit data from the sensor along appropriate lines e g wire or fibre optic lines is then attached to the sensor and fed downhole with one or more later sections of completion pipe attached to the sensor carrying pipe, further sensor pipe is added as required and the sensors joined up with cable The rest of the completion and then production string is then attached and run downhole, and then well head completed In the case of resistivity measurements, the sensor pipe is insulated from neighbouring pipe and electrical connections arc made to the sensor pipe and neighbouring pipe The reservoir completion pipe is then perforated and oil/gas production started. During production continuous or continual measurements from the sensors can be taken From the results, parameters such as water content can be determined, and in response to the data, the recovery process can be altered if required to optimise production e g avoid water coning

The devices of the invention may be used to provide information of flow in the well, as well as flows near the well and between neighbouring wells e g via resistivity measurements, and can replace use of many separate periodic reservoir surveillance logging operations, particularly under the sea (e.g. in subsea completed wells) where such operations are difficult and expensive. The devices may also be used at different levels in the reservoir, whereas present devices give measurement at only one depth, above the reservoir and in the last cemented casing section of the well. Resistivity of the fluid cannot be determined in the latter case, whereas this can be easily performed with the devices of the invention.

Thus the devices of the invention with a resistivity sensor can be used to measure resistivity in the near well bore region (up to lm from the bore), and would be an improvement on pulsed neutron and carbon oxygen existing equipment in low salinity and low porosity environments. With a second well nearby also carrying a resistivity sensor on the pipe, well resistivity tomography could be used to monitor the movement of flood fronts across the reservoir. Surface electrodes in combination with the resistivity devices of the invention can be used to map the resistivity and thus saturation changes across a reservoir. In resistivity uses, the completion pipe is effectively transformed into an array of resistivity electrodes by the insertion between 2 or more standard sections of the completion pipe (each about 10 metres long) of insulated sections or joints, usually short joints, of completion pipe of the invention (which also carry an resistivity electrode and can also carry other sensors) thus effectively insulating each joint of the completion pipe from its neighbours. Each section or joint of pipe (both the sensor carrying insulated joints and the conventional 10m section) is individually connected to the surface [as exemplifying the data collection point] and each constitutes one electrode of an array of resistivity electrodes, for use in combination with one or more other resistivity electrodes, which may be on the surface of the formation [e.g. spaced from the well head] or on an electrical connection from a neighbouring completion pipe, which may be above or below the sensor. The neighbouring pipe in question may be one joined directly to the pipe carrying the sensor or acting as the resistivity electrode, or may be spaced therefrom by one or more sections of completion pipe and/or pipes carrying sensors. Alternatively the other resistivity electrode may be another resistivity electrode in the same pipe string, with electrical connection to the surface. Finally the other resistivity electrode or electrodes may be on a neighbouring well, and may be a completion pipe or a pipe carrying a resistivity electrode again supplied with connection to the surface. Voltages can be applied across any combination of the resistivity electrodes in pairs, trios (e.g. the combination of sensor, completion pipe and sensor, or the combination of completion pipe, sensor and completion pipe) or multiples in order to determine the resistivity of the formation either locally to the well with respect to depth or between two or more wells In cases where the resistivity of the formation at a particular depth local to the well is sought, the completion pipes above and below the resistivity electrode at that depth can be charged separately as guard electrodes to a voltage similar to that to which the measure electrode is charged, this has the effect of focusing the movement of the current [and hence the resistivity measurement] at the depth required

Devices of the invention with a pressure sensor can be used to provide in real time information on fluid pressure gradients of the formation, e g identification of pressure boundaries and zones at different reservoir pressure in deviated (e g substantially horizontal) wells and vertical wells in layered reservoirs with cemented casings In addition identification and monitoring of oil/water and gas/oil contacts from the gradient lines when the well was shut in, are possible as is identification of gas saturation in draining gas caps, by using the pressure gradient in conjunction with near well pressure analysis These pressure sensors could replace individually run cased hole neutron logs, saturation monitoring tools and borehole density (gradiomanometer) tools

Devices with ultrasonic sensors can measure fluid velocity and relative proportions of produced fluids to determine water production An array of several of such sensors on pipes along the reservoir length enables individual fluid velocities to be measured and fluid interface (and thus relative proportions of produced fluids) to be monitored in oil/water mixtures containing up to about 30% gas (by volume) These devices would replace separate running of phase velocity, oxygen activation and spinner logs inside the casing

Devices with temperature sensors can be used as gas entry indicators The present invention is illustrated in the following drawings in which Figs 1 and 3 represent cross sections of two sensor pipes of the invention and Fig 2 represents a cross section of cemented casing above a reservoir, with the sensor pipes of the invention and completion pipes in the reservoir

Referring now to Fig 1 pipe 1 is in the form of a stub joint usually 1 -7ft (0 3-2 13m) or 0 5-2m long It has threaded connection ends 2 and 3, being internally and externally threaded respectively, for engagement with corresponding threads on adjacent completion pipe A sensor package 4 in the form of a sheath or housing is located around the outside of the pipe 1 about its middle and is welded thereto On the outer surface of the package 4 is a circumferential slot 5 in which a resistivity sensor 6 is located. On the side of the package 4 distant from the sensor 6 are 2 external pressure sensors 7 located in outwardly facing radial grooves 8 in the package 4 Between sensors 7 and pipe 1 but facing inwardly is an internal temperature sensor 9 shown located in its slot 10 in pipe 1 but preferably located in the housing package 4 and usually in thermal communication with pipe 1 and/or the outside of package 4 On the opposing internal face of pipe 1 to sensor 9 is located an internal pressure sensor 11 present in a passage 12 extending outwardly through the pipe wall, but capped by package 4 Embedded in said opposing internal face of pipe 1 is an internal flow sensor 13, in particular an ultrasonic one aimed across the internal width of the pipe 1 and preferably at an angle to the transverse axis thereof either up or down stream Threaded connection ends 3 are coated with an electrically insulating layer 14 Cable 15 contains the electrical leads (not shown) leading from each of the sensors via the part of the package near the location of the resistivity sensor 6 to the data analysis system, usually at the wellhead or surface Cable 15 also contains corresponding leads from other pipes 1 In an alternative version of the pipe 1 (not shown) the sheath may have a cavity defined by the outer wall of the sheath 4 and the outer wall of the pipe 1 , the cavity containing the cable 15 and junctions with the electrical leads to/from the sensor

Referring now to Fig 2 the last section of casing 20 is cemented in place and has a production tubing 21 extending coaxially through it and separated from it by packers 22 Production tubing 21 has cabling 30 strapped on its outside Coaxially surrounding the tube 21 and extending downwardly beyond it is a reservoir completion pipe 23, which is supported via liner hanger 24 by casing 20 Reservoir completion pipe 23 is in electrical contact with cable 30 on production tubing 21 via wet connect/inductive couplings 25, which are in electrical contact with cable 15 extending down the outside of pipe 23 but insulated therefrom Reservoir completion pipe 23 is interrupted by several sensor pipes 1 spaced along its length, the pipes having packages 4 joined to the cable 15 In several places down the length of reservoir completion pipe 23 and preferably all on the same side of the pipe 23 distant from the cable 15 are perforations 26

In use reservoir completion pipe 23 is run down hole with perforatable sections, and spaced down its length are sensor pipes 1 Each sensor pipe 1 is attached by the insulating threads 3 and 4 to the section of pipe 23 below and above it (respectively) Each pipe 1 is carefully aligned so the cable 15 is in the same location as in lower pipes 1 Cable 15 is then strapped to the pipe 1 (not shown) and then to the section(s) of reservoir completion pipe 23, above it Then a further sensor pipe 1 is threaded onto pipe 23 and the leads from the sensors fed into the cable 15 Cable 15 is then strapped to that pipe 1 (not shown) and then to the section(s) of pipe 23 above it etc The cable 15 is stopped on the section of reservoir completion pipe 23 which will be located just below the cemented casing 20. Further sections of reservoir completion pipe 23 are then threaded on as a liner for inside casing 20 and for joining to casing 20 via liner hanger 24 and the sections run down hole Production tubing 21 is then run down hole, the lowest section carrying the coupling 25 The location of tubing 21 is adjusted so coupling 25 corresponds to the part of reservoir tube 23 carrying the uppermost part of cable 15 Packers 22 are run with the production tubing 21

During assembly of the entire pipe string, the electrical circuits for the sensors are tested to ensure continuity and operation from cabling 30, coupling 25, cable 15 and the sensors in the packages 4

The reservoir completion pipe 23 is then perforated with a perforating gun (not shown) and then production started Continuously or continually the output from the sensors is monitored to provide information on the conditions in different parts of the reservoir, and appropriate action if any taken

Resistivity electrode sensor 6 usually has a wire connecting it electrically to the surface and a voltage is applied between it and a corresponding wire connected to the neighbouring completion pipe (not shown) from which pipe 1 is insulated bv coating 14 The voltage and current obtained provides a measure of the resistivity of the formation around the pipe 1 between sensor 6 and the neighbouring pipe (not shown)

Referring now to Fig 3, pipe 1 is as in Fig 1 with connection ends 2 and 3, having insulated layers 14 as in Fig 1 Instead of package 4, the pipe 1 has a central outwardly extending wall portion 31 of greater thickness than the wall thickness nearer the ends 2 and 3 In this portion 31 is a circumferential slot with resistivity sensor 6 Two external pressure sensors 7 are in portion 3 1 in radial slots 8 which are spaced by slot 5 Between slot 5 and slot 8 is a chamber 30 containing temperature sensor 9 Slots 8 and chamber 30 are in communication with grooves 32 and 33 respectively which extend circumferentially round wall portion 31 and contain wires or fibres (not shown) leading from sensoi s 7 and respectively to a junction box 34. An internal pressure sensor 11 is in passage 12 extending outwardly from the inside of pipe 1, but closed by wall portion 31. In the internal face of pipe 1 is an internal flow sensor 1 as in Fig.1. Junction box 34 is received in a longitudinal valley in wall portion 31 and houses the end of the wires/fibres from the sensors, the ends joining to leads (not shown) in Cable 15 which extends from the junction boxes of other sensor pipes 1 above and below pipe 1 of Fig.3 leading to the data analysis system. Each slot or groove may be individually capped (e.g. as shown with threaded lid 35 on slot 8) or a thin sheath cap may surround all the slots or grooves, e.g. by generally surrounding the thicker wall portion 31.

The pipe of Fig.3 is used in the same way as the pipe of Fig.1.

Claims

Claims.

1 A reservoir completion pipe characterised in that said pipe is provided with at least one external sensor

2 A pipe as claimed in claim 1 wherein said pipe is also provided with at least one internal sensor 3 A pipe as claimed in any of the preceding claims wherein said pipe is provided with 2-6 sensors

4 A pipe as claimed in any of the preceding claims which comprises at least two different sensors

5 A pipe as claimed in any one of the preceding claims wherein the external or internal sensor is a pressure sensor, a temperature sensor, a low energy density sensor, a flowmeter or a resistivity electrode

6 A pipe as claimed in any one of the preceding claims wherein the external sensor is a resistivity electrode

7 A pipe as claimed in claim 6 wherein the resistivity electrode is of the multi- electrode type

8 A pipe as claimed in claim 6 or 7 together with at least one of a pressure and temperature sensor

9 A pipe as claimed in any of the preceding claims wherein the external sensor is in a framework which is itself externally mounted on the pipe or in a housing mounted externally on the pipe

10 A pipe as claimed in claim 9 wherein the housing is in the form of a sheath

1 1 A pipe as claimed in any one of the preceding claims wherein at least one sensor is in a slot in the external wall of the pipe

12 A pipe as claimed in any of the preceding claims wherein the pipe has at least one threaded end 13 A reservoir completion pipe as claimed in claim 12 wherein the threaded end carries an electrically insulating coating

14. A pipe as claimed in any of the preceding claims which also comprises an electric cable leading from the or each sensor to transmit data from said sensor to a distant data analysis system

15 A pipe string comprising a completion tube characterised in that at least one section of said completion tube is attached to a reservoir completion pipe as claimed in any of the preceding claims

16 A method of determining a parameter in a reservoir which comprises passing down a hole into said reservoir a sensor and measuring said parameter characterised by passing a reservoir completion pipe as claimed in any of claims 1-

14 and measuring said parameter

17 A method according to claim 16 wherein the parameter is the resistivity of the reservoir 18 A method of producing oil or gas from a subterranean reservoir via a tube which comprises passing a plurality of sections of production and reservoir completion pipe down said well into said reservoir and withdrawing oil and/or gas therefrom characterised in that oil and/or gas is withdrawn through said pipe of which at least one section is as claimed in any of claims 1 - 14 or through a pipe string as claimed in claim 15 while the sensor measures one or more reservoir parameters