GB2472391A

GB2472391A - Method and apparatus for determining the location of an interface region

Info

Publication number: GB2472391A
Application number: GB0913504A
Authority: GB
Inventors: Graeme George Mcrobb; Daniel Andrew Watley; Neale Carter
Original assignee: Sensornet Ltd
Current assignee: Sensornet Ltd
Priority date: 2009-08-03
Filing date: 2009-08-03
Publication date: 2011-02-09
Also published as: GB0913504D0

Abstract

A method and apparatus for determining the location of an interface region between at least two components of a medium within a subterranean environment comprises isolating at least one zone within a subterranean environment, heating a medium within the at least one isolated zone, measuring a rate of change of temperature at different locations within the medium, and identifying an interface region between at least two locations with different measured rates of change of temperature. The method may comprise measuring temperature at different location by one or more thermal imaging apparatus, such as a thermal imaging camera, or by at least one distributed temperature sensor arrangement. An apparatus 30 for locating interfaces 20, 22 may be located within a wellbore 10 and comprises tubular support member 32 which includes a plurality of swellable packers 34. The packers, once activated to create a seal define a number of isolated annular zones 40. Measurements may be taken within these isolated zones to determine the location of interfaces 20, 22.

Description

MEASUREMENT METHOD AND APPARATUS

FIELD OF THE INVENTION

The present invention relates to a measurement method and apparatus for use in determining the location of an interface region between two components of a medium, and in particular, but not exclusively, to a downhole measurement method and apparatus for use in determining the location of an interface between oil and water components of a reservoir or formation.

BACKGROUND TO THE INVENTION

In the oil and gas exploration and production industry, wellbores are drilled into the earth to intercept subterranean hydrocarbon bearing formations or reservoirs to permit the hydrocarbons to be produced to surface. The conditions within the wellbore and formation can have a significant influence on many aspects associated with the well, such as well infrastructure, production rates and the like. Accordingly, it is extremely desirable to perform a number of measurements associated with the wellbore, and even the formation, to identify particular in situ conditions. Such measurements may include pressure, temperature, vibration, chemical composition, geological conditions or the like. These measurements may simply be used for monitoring purposes, improving reservoir management, and/or may be used to assist in identifying a requirement to take appropriate intervention or remedial action to ensure desired well conditions, such as production rates, can be achieved and S...

*::: : maintained. Furthermore, appropriate measurements may provide information relating to the effectiveness, or otherwise, of any remedial action taken.

A hydrocarbon bearing formation or reservoir normally contains both hydrocarbon liquids and gases, and will invariably also contain water. In fact, in many wells water is injected into the formation to assist with production of hydrocarbons, a technique which is often used in depleted wells (i.e., wells which have been producing for a period of time such that the formation pressure can no longer sustain un-assisted production of hydrocarbons to the surface). Although a degree of mixing of the hydrocarbons and water occurs in the formation, the formation components are usually stratified into relatively well defined layers, conventionally with an upper layer of gas, an intermediate layer of oil and a lower layer of formation water, which may include injection water, with respective interfaces therebetween.

Significant efforts are made to minimise the volume of formation water, or injection water, which is produced to the surface, as producing water restricts the hydrocarbon production efficiency of the well, and creates problems such as separating the water from the valuable hydrocarbons, handling and disposing of the produced water and the like. The problems of water production are well documented in the art.

It is therefore highly desirable to have an understanding of the location of the interfaces within a formation, particularly the oil/water interface. This may be of use in minimising water production, or in identifying the effectiveness, or otherwise, of a water injection operation. For example, having a precise understanding of the location of the oil/water interface may assist in establishing the most efficient path of a production welibore.

Furthermore, movement of the interfaces between the different layers in a **0 formation occurs over the course of time as the hydrocarbons are produced, or as * * * ** * water is injected, and it is often the case that a water interface will encroach into a production zone. In such circumstances it may be necessary to isolate this production zone. It would therefore be advantageous to identify an approaching interface. S **

Existing techniques of identifying interfaces within geological formations include performing geological surveys, typically seismic surveys. However, it is recognised in the art that the accuracy and sophistication of the data from existing seismic techniques may be insufficient to identify geological interfaces at the level of accuracy desired.

It is known in the art to take measurements from within a production well which is, or is intended to, produce hydrocarbons. A variety of measurement or logging techniques are known in this regard. For example, in some cases well activity may be ceased to permit a workover or intervention operation to be performed to take the necessary measurements, for example by deploying logging equipment into the well on wireline, followed by appropriate analysis and then any appropriate remedial action. However, ceasing well activity, especially production, is not desired due to the associated loss/delay of production. It is therefore also known in the art to create an observation well within the vicinity of a production well, with the assumption that the conditions within the observation well and surrounding formation will be similar to that of the production well. This approach to measurement may reduce the complexities associated with measuring or logging within a production well which contains a significant amount of completion infrastructure and the like.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method for determining the location of an interface region between at least two components of a medium within a subterranean environment, comprising: heating the medium; measuring a rate of change of temperature at different locations within the S..,.

medium; and **�(

S

identifying an interface region between at least two locations with different : 25 measured rates of change of temperature.

Accordingly, the presence of different rates of change of temperature at at least two locations within the subterranean environment may permit a determination to be made of the existence, and location, of an interface region between said at least two locations.

The at least two locations with different measured rates of change of temperature may comprise at least two adjacent locations.

The present invention may be utilised to identify an interface region between two components of a medium which have different thermal properties. The present invention may be utilised to identify an interface region between two components having different heat capacities. That is, a component with a higher heat capacity will provide a smaller rate of change of temperature than a component with a lower heat capacity.

The method may be for use in determining the location of an interface region between at least two components of a medium which comprise a similar material, element, compound or the like. In this arrangement the components may comprise differing chemical properties, such as salinity or the like. For example, an aqueous solution having a higher salt concentration may exhibit different thermal properties from an aqueous solution having a lower salt concentration. This arrangement may permit an interface region to be identified between, for example, formation water and injection water, Identifying such an interface may be advantageous in permitting monitoring of the effect, location, migration or the like of water which has been injected into a formation, for example for matrix support, artificial lift of subterranean * *. formation or reservoir fluids to surface or the like. * * * ** S

The method may be for use in determining the location of an interface region between at least two components of a medium which comprise different materials. In one embodiment one component may comprise water, and another component may comprise a hydrocarbon, such as oil, Identifying an interface between water and oil S..

may be advantageous in permitting monitoring in the region of a production zone (i.e., a zone from which a formation fluid is drawn to be delivered to surface, for example). This may assist in the prevention, or limitation, of water being produced to surface. For example, the identification of an oil/water interface approaching a production zone may permit the production zone, or a portion thereof, to be isolated, for example by swellable packers or the like.

The method may be for use in determining the location of an interface region between at least two components of a medium which comprise different phases, such as solid, liquid and/or gas phases.

The method may comprise determining the location of an interface region between at least two components of a medium within a subterranean formation. The method may comprise determining the location of an interface region between at least two components of a medium within a weilbore which extends through a subterranean formation. In this arrangement it may be assumed that a location of an interface region within the wellbore is substantially equivalent to a corresponding interface region within the formation.

The weHbore may comprise a production welibore. The weilbore may comprise an observation welibore. The wellbore may comprise an injection wellbore, exploration weilbore or the like.

The welibore may be vertically orientated. The weilbore may be inclined.

The wellbore may be horizontally orientated.

The method may comprise the step of characterising a component of the medium. For example, a particular rate of change of temperature may be indicative of a particular component, or a particular property of a component. The method may * II comprise measuring the rate of change of temperature at at least one location within the medium, and then identifying or characterising a component, or a property of a component of the medium based on the measured rate of change of temperature.

: 25 The method may comprise the use of calibration data, such as look up tables or the like. I. I * I,

* The method may comprise determining a profile of the rate of change of temperature between a number of different locations within the medium. Such a profile may permit a location of an interface between at least two components of the medium to be identified. Such a profile may permit one or more properties of the interface region to be determined, estimated, derived or the like, such as a thickness of the interface region.

The method may comprise measuring temperature at different locations by a plurality of temperature sensors distributed within or adjacent to the medium. For example, individual temperature sensors may be distributed along a desired dimension relative to the medium, and record, sense or measure the temperature, and the variation thereof with respect to time.

The method may comprise measuring temperature at different locations by one or more thermal imaging apparatus, such as a thermal imaging camera.

The method may comprise measuring temperature at different locations by at least one distributed temperature sensor arrangement, such as an optical distributed sensor arrangement. Distributed temperature sensor arrangements are known in the art. Distributed temperature sensors usually use Raman scattering in optical fibres as the means to determine the temperature. Here, light from a laser source is sent down a fibre and the small amount of light that is scattered back towards the source is analysed. By using pulsed light and measuring the returning signal as a function of time, the backscattered light that was generated at all points along the fibre can be determined. This backscattered light contains components that are up-and down-**.* : shifted in frequency from the source light (Raman and Brillouin anti-Stokes and S...

Stokes light respectively) and light that is elastically scattered (Rayleigh light). The *S..

powers of the returning Raman and Brillouin signals are temperature dependent and so analysis of these components yields the temperature. Usually, the Raman Stokes and anti-Stokes signals are used to determine the temperature however sometimes *..: the Rayleigh light is used as a reference and sometimes the Brillouin components are used. The Rayleigh light, and sometimes the Raman Stokes light, is often used to measure the loss along an optical fibre.

The method may comprise selecting a resolution of a distributed temperature sensor arrangement in accordance with the particular use. In one embodiment a resolution of less than im may be selected, such that interface features may be resolved to the locality of lm. The resolution may be less than 50cm, and may be less than 30cm. A shorter spatial resolution may permit greater accuracy in the determination of an interface region.

The method may comprise measuring temperature at different locations indirectly. For example, the pressures, or partial pressures, within the medium may be measured or determined, and subsequently used to determine temperatures.

The method may comprise heating the medium with a heater, such as a resistive heater. The method may comprise heating the medium by radiation, such as by microwave radiation. The method may comprise heating the medium by mechanical agitation, such as by directing sonic or ultrasonic waves into the medium.

The method may comprise running a support member into a welibore. The support member may support at least one heater. The support member may support at least one temperature sensor. The support member may comprise a tubular, such as a tubing string. The tubular may comprise a drilling tubular, casing tubular, liner tubular, casing tubular, production tubular or the like. The support member may comprise wirelirie, coiled tubing or the like.

The method may comprise isolating at least one zone within a subterranean *.S.

: environment, and then determining the location of an interface region between at * * least two components of a medium within the at least one isolated zone.

Establishing an isolated zone within which to determine the location of an interface may permit increased control of the method. For example, the ability to determine a particular region may permit improved heating of said region, and/or improved * temperature measurement within said region.

The method may comprise isolating a region within a wellbore, such as an annular region.

The method may comprise isolating a region within a welibore using at least one seal arrangement. The seal arrangement may comprise a packer. The seal arrangement may comprise a swellable material configured to swell upon exposure to a swelling activator. The swellable material may be adapted to be activated by a chemical activator, thermodynamic activator, fluid dynamic activator, or the like, or any suitable combination thereof. For example, the swellable material may be adapted to be activated by a fluid, such as water, hydrocarbons, cement, drilling mud, or the like, or any suitable combination thereof. The swellable material may be selected to swell upon exposure to fluids or conditions present in a subterranean environment. The swellable medium may be adapted to be activated by heat, pressure, radioactivity or the like.

The use of at least one seal arrangement may permit a support member or the like to be sealed within a wellbore. This may eliminate, or at least minimise, the requirement to seal a support member within a bore using conventional methods, such as by using cement. Such conventional sealing methods would require the support body to be perforated to provide communication with a subterranean formation.

According to a second aspect of the present invention there is provided an apparatus for use in determining the location of an interface region between at least two components of a medium within a subterranean environment, said apparatus comprising: I... * *

a heater configured to heat the medium; and **** * : a temperature sensor arrangement configured to measure a rate of change of temperature at different locations within the medium.

The apparatus may comprise a support member. The support member may * be configured to support one or both of the heater and temperature sensor arrangement. The support member may comprise a tubular or tubing string or the like.

The support member may be configured to be located within a wellbore which extends through a subterranean formation.

The apparatus may comprise one or more sealing arrangements configured to isolate one or more regions within a subterranean environment. The seal arrangement may comprise a swellable material.

The heater may comprise a resistive heater, radiation source, sound source or the like.

The temperature sensor arrangement may comprise a distributed temperature sensor arrangement.

The apparatus according to the second aspect may be suitable for use in performing the method according to the first aspect. Accordingly, features defined above in relation to the first aspect may apply to the second aspect.

According to a third aspect of the present invention there is provided a method for determining a property change of a medium in a region, comprising: heating a medium contained within a region; measuring a rate of change of temperature within the medium; and identifying a variation in the rate of change of temperature to indicate a change in a property of the medium.

The property change may comprise the replacement of one medium with another medium within the region.

.. : The property change may comprise a change or distribution of separate *I*.

components within a medium.

: The variation in the rate of change of temperature may be with respect to time, such that the property change occurs over a temporal period. For example, one type of material may displace another from the target region over a temporal period. This arrangement may be advantageous in determining the encroachment of water into a subterranean production zone, for example.

The variation in the rate of change of temperature may be with respect to a dimension of the region. This may permit identification of an interface between two different components of a medium within the region.

The region may comprise a region of a subterranean formation. The region may comprise a region of a weilbore, such as a wellbore which extends through a subterranean formation. The region may comprise an isolated region. The isolated region may be isolated using one or more sealing arrangements, such as packers.

The sealing arrangement may comprise a swellable material.

The region may comprise an annular region, such as a welibore annulus, for example defined between a tubing string and a wall of a wellbore.

Aspects of the present invention may also relate to an apparatus suitable for performing the method according to the third aspect.

According to a fourth aspect of the present invention there is provided a method for determining the location of an interlace region between two components of a medium, comprising: heating the medium; measuring a rate of change of temperature at different locations within the medium; and identifying an interface region between at least two locations with different measured rates of change of temperature. S...

: The method may be for determining the location of an interface region S...

S... between two components of a medium within a subterranean environment, such as a S...

: subterranean formation, welibore or the like. The method may be for determining the location of an interface region between two components of a medium within a conduit or the like. This arrangement may have application in flow monitoring, such as *..: multiphase monitoring, within a pipeline.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of an apparatus for use in determining an interface region in a subterranean environment, in accordance with an embodiment of the present invention; Figure 2 is a diagrammatic representation of an apparatus for use in determining an interface region in a subterranean environment, in accordance with an alternative embodiment of the present invention; and Figures 3A and 3B represent an apparatus and method for determining the encroachment of water into a production zone according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figure 1 in which there is shown a drilled observation wellbore 10 which extends through a hydrocarbon bearing subterranean formation 12. The observation wellbore 10 is provided in the vicinity of a production welibore (not shown) which extends through the same formation 12. In this case the observation wellbore 10 is established to permit various observations, measurements and the like to be performed, with the assumption that conditions within the observation wellbore 12 will largely reflect conditions within the production wellbore.

*..* : This permits suitable measurements to be taken without the complexities of taking S...

these directly from within the production bore.

In the embodiment shown the formation 12 includes a region of oil 14, a region of formation water 16, and a region of injection water 18. An interface region is defined between the oil and formation water regions 14, 16, and an interface region 22 is defined between the formation water and injection water regions 16, 18.

The interface regions 20, 22 are illustrated by a single line. However, it will be recognised by a person of skill in the art that the interface region may be of a significant thickness, and may comprise an emulsion, mixture or the like of the individual components located in the separated regions 14, 16, 18.

As will be discussed in further detail below, the present embodiment illustrated in Figure 1 is for use in determining the location of the interface regions 20, 22. This may provide extremely valuable information. For example, understanding or having knowledge of the location of the oil/formation water interface 20 may permit an operator to minimise, avoid, or take action against the production of the formation water to surface through the production weilbore. Additionally, being able to determine the formation water/injection water interface 22 may provide knowledge of the migration, influence or the like of water which has been injected into the formation 12, for example to assist in the production of oil to surface.

An apparatus, generally identified by reference numeral 30 for use in determining the location of the interfaces 20, 22 is located within the wellbore 10.

The apparatus 30 comprises a tubular support member 32 which includes a plurality of swellable packers 34 distributed along the length thereof. The packers 34 are configured to swell upon exposure to an activating medium, such as water or hydrocarbons, to create a seal within the annulus 36 formed between the tubular member 32 and a wall 38 of the wellbore 10. The packers 34, once activated to create a seal, define a number of isolated annular zones 40. It is within these isolated zones 40 that measurements may be taken to determine the location of the S..

: interfaces 20, 22. In this respect, and as illustrated in Figure 1, the formation * S..

* interfaces 20, 22 result in corresponding interface levels 20a, 22a within the wellbore *5S* : annulus 36. Thus, determining the location of the annulus interfaces 20a, 22a permits the corresponding formation interfaces 20, 22 to be determined.

The use of packers 34 to seal the tubular support member 32 within the wellbore 10 may eliminate the requirement to use a conventional sealing approach of cementing the tubular member 32 within the wellbore 10, which would then require perforation to establish communication with the formation 12.

The apparatus 30 further comprises a number of resistive heaters 42 located within the respective zones 40, wherein the heaters 42 are configured to heat the medium contained within each zone 40. In the embodiment shown the heaters 42 are formed by coils wrapped around the surface of the tubular 32. The heaters may be provided on pup joints secured to the tubular 32.

The apparatus 30 further comprises a fibre optic distributed temperature sensor (DTS) 44 which runs along the length of the tubular 32, through each packer 34 and isolated zone 40. The DTS 44 is configured to measure the temperature of the medium along a desired length of the annulus 36. The DTS 44 may be configured to have a spatial resolution of around lm such that the sensor is capable of resolving temperatures to the locality of around 1 m spacing. However, a different spatial resolution may be selected, for example if a greater degree of accuracy is required. The DTS is therefore capable of measuring or determining the temperature at a number of locations within the annufus 36.

In use, the heaters 42 are activated to heat the medium which has flowed, seeped or leached into the annulus 36 from the formation 12, and the rate of change of temperature (i.e., the temperature change with respect to time) of the medium is determined at a number of locations within the annulus, by use of the DTS 44.

Where the rate of change of temperature is determined at two locations to be substantially the same or similar, it may be assumed that the properties of the *..* : medium at these locations are substantially the same. This may be the case in zone S...

40a where only oil is present, or in zone 40c where only formation water is present. S...

However, where the rate of change of temperature is determined at two locations to be different, it may be established that the properties of the medium at these locations are different. For example, in zone 40b, in which the annulus . .: medium contains both oil and formation water, the rate of change of temperature will be different at a location above the interface 20a (i.e., oil), than at a location below the interface 20a (i.e., formation water). This is due to the difference in the thermal properties (e.g., heat capacity) of oil and formation water. That is, oil has a lower heat capacity than water, and thus its temperature will increase faster than water.

If a difference in the rate of change in temperature is identified between two locations, then it can be assumed that an interface region exists between these two locations.

According'y, differences in the rates of change of temperature at locations within zone 40b will permit the location of interface 20a to be determined, and similarly differences in the rates of change of temperature at locations within zone 40d will permit the location of interface 22a to be determined. In this respect, it should be noted that in most cases the chemistry of formation water and injection water differs (for example salinity may differ), which results in the formation water and injection water having different thermal properties, permitting interface 22a to be determined by use of the method and apparatus described herein.

Figure 2 shows an apparatus, generally identified by reference numeral 50, in accordance with an alternative embodiment of the present invention. The apparatus is similar to apparatus 30, and is intended to function in a similar manner. That is, the apparatus 50 is for use in a wellbore 10 to determine the location of an interface between a region of oil 14 and a region of formation water 16, and the location of an interface 22 between the formation water region 16 and a region of injection water.

: In a similar manner to that described above, the apparatus 50 comprises a S..' tubular support 32 and a number of axially spaced swellable packers 34 which define S...

.. isolated zones 40 therebetween However, in the present embodiment the apparatus comprises a heater cable 52 which contains regions of high resistance 54 :.:5 arranged to be positioned within respective isolated zones 40 to heat a medium S. S . .: contained therein.

The apparatus 50 further comprises a plurality of discrete temperature sensors 56 distributed along the length of the tubular support 32 and configured to measure the temperature of a medium at discrete locations along the annulus 36.

The operation of the apparatus 50 is similar to that of apparatus 30 described above, and as such no further description will be provided.

In both Figures 1 and 2 the apparatuses 30, 50 are shown in use within a vertical wellbore 10, However, the apparatuses 30, 50 have application in wells of varying orientation, such as in horizontal wells. In this respect reference is now made to Figures 3A and 3B in which a further exemplary use of the apparatus 30 is illustrated (apparatus 50 may also be used in the same manner, but for the purposes of brevity, apparatus 30 has been selected for the present exemplary case).

In this case the apparatus 30 is shown located within a horizontal bore 60 which extends through a subterranean formation 12 having a region of oil 14 and a region of formation water 16, with an interface 20 defined therebetween. In the embodiment shown the wellbore 60 is a production welibore which is used to produce oil from region 14 to surface.

As shown in Figure 3A, the oil/water interface 20 is located below the level of the wellbore 60 such that only oil from region 14 may flow into the wellbore 60 to be produced to the surface. However, over the course of time the interface 20 will encroach towards the production wellbore 20 until eventually water will reach the .. : level of the wellbore 60, as shown in Figure 3B. As previously noted, it is highly *...

desirable to minimise the volume of formation water which is produced to the surface, *.S.

. : as producing water restricts the hydrocarbon production efficiency of the well, and creates problems such as separating the water from the valuable hydrocarbons, handling and disposing of the produced water and the like.

In the embodiment shown, the apparatus 10 provides an indication to an operator that the interface region 20 has encroached into the level of the wellbore 60, as will be discussed in detail below.

The heaters 42 are activated to heat a medium contained within the annulus 62, and the DTS 44 will measure or monitor the change in temperature of the medium, to thus establish the rate of change of temperature of the medium. This process may be repeated cyclically, for example every hour, minute or the like.

When the interface 20 is located below the wellbore 60, as shown in Figure 3A, the medium within the annulus 62 will primarily comprise oil, and as such the result of each measurement should be substantially consistent. However, as the interface 20 encroaches into the wellbore 60, as shown in Figure 3B, the composition of the medium within the annulus 62 will change to include water, and as such a variation in the rate of change of temperature will be identified. Upon detection of this variation it may be assumed that the interface region has encroached into the wellbore 60, and as such appropriate remedial action may be taken, such as isolation of the effected production zone, for example by activating packers, such as swellable packers.

It should be understood that the embodiments described above are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, the packers utilised to provide individual isolated zones may be eliminated. Additionally, any suitable form of heater or heating method may be utilised. For example, a radiation based heating method may be utilised, such as microwave radiation heating. Additionally, any suitable method or form of temperature measurement may be used, and may include thermal I...

: imaging or the like. Additionally, a measurement of temperature may be provided * *** indirectly, for example by measuring pressure, volume or the like. *.** * *. ** * * ** * * * 0* * S. *

S * *.