WO2011010101A2 - Downhole apparatus and method - Google Patents

Downhole apparatus and method Download PDF

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Publication number
WO2011010101A2
WO2011010101A2 PCT/GB2010/001392 GB2010001392W WO2011010101A2 WO 2011010101 A2 WO2011010101 A2 WO 2011010101A2 GB 2010001392 W GB2010001392 W GB 2010001392W WO 2011010101 A2 WO2011010101 A2 WO 2011010101A2
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WO
WIPO (PCT)
Prior art keywords
interface
signal
subterranean
downhole
relative distance
Prior art date
Application number
PCT/GB2010/001392
Other languages
French (fr)
Other versions
WO2011010101A3 (en
Inventor
Rudd Wayne
Original Assignee
Rudd Wayne
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rudd Wayne filed Critical Rudd Wayne
Publication of WO2011010101A2 publication Critical patent/WO2011010101A2/en
Publication of WO2011010101A3 publication Critical patent/WO2011010101A3/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
    • G01V3/30—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with electromagnetic waves
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B44/00—Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/02—Determining slope or direction
    • E21B47/022—Determining slope or direction of the borehole, e.g. using geomagnetism
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/02—Determining slope or direction
    • E21B47/026—Determining slope or direction of penetrated ground layers
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/04—Measuring depth or liquid level
    • E21B47/047—Liquid level
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B7/00—Special methods or apparatus for drilling
    • E21B7/04—Directional drilling
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/40—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging
    • G01V1/44—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging using generators and receivers in the same well
    • G01V1/46—Data acquisition
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/40—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging
    • G01V1/44—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging using generators and receivers in the same well
    • G01V1/48—Processing data
    • G01V1/50—Analysing data
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V11/00—Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
    • G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/38—Processing data, e.g. for analysis, for interpretation, for correction

Definitions

  • the present invention relates to a downhole apparatus and method, and in particular to a downhole apparatus and method for determining the position of an interface within a subterranean formation.
  • geological investigations are performed to determine, as accurately as possible, the presence and location of subterranean hydrocarbon bearing formations or reservoirs.
  • the geological investigations may utilise seismic techniques, typically involving initiating explosions at surface level and analysing the reflections of these explosions from the earth to develop an estimation of the geological make-up of the region under investigation. Regions of interest may be further explored by drilling investigatory bores and taking geological samples for subsequent analysis, for example.
  • one or more well bores are drilled in the earth, often extending thousands of feet, to intercept the identified reservoirs and provide a path to produce the hydrocarbons to surface.
  • the wellbores are drilled using a drill string formed by a drill bit mounted on the end of a tubing string of drill pipes and collars.
  • the bore is completed by running in a production tubing string which extends between the surface and the reservoir.
  • the production tubing string is arranged to be in fluid communication with the reservoir at one or more desired locations.
  • the locations of fluid communication are typically called production zones.
  • a hydrocarbon bearing formation normally contains both hydrocarbon liquids and gases, and will invariably also contain water. 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 liquid hydrocarbons and a lower layer of formation water, with respective interfaces therebetween
  • the data produced from geological exploration surveys may be used to determine a desired path of the drill string, for example to avoid regions with large volumes of formation water
  • accuracy and sophistication of the data from existing seismic techniques may be insufficient to ensure that an optimum course of a drilled well bore is achieved
  • a downhole apparatus for identifying the position of an interface within a subterranean formation, said apparatus comprising a signal emitter configured to emit a signal; and
  • a signal receiver configured to receive the signal following reflection from a subterranean interface
  • a relative distance between the apparatus and the subterranean interface is determined from a characteristic of the reflected signal.
  • the downhole apparatus of the present invention may permit a downhole assessment of the relative location of a subterranean interface.
  • the apparatus may permit initial identification of the interface, monitoring of the interface or the like.
  • the apparatus may be configured for use in ensuring that a desired location of the apparatus, and any associated apparatus or equipment, relative to a subterranean interface is achieved and/or maintained.
  • the subterranean interface may be defined by a condition change within a subterranean environment.
  • the condition change may comprise a material change.
  • the condition change may comprise a bulk material change, such as a change from one geological type or structure to another, or a change or variance in a material which is held within a subterranean structure, such as a porous structure, or otherwise.
  • the interface may be defined between a region predominantly containing water and a region predominantly containing hydrocarbons.
  • the interface may be defined between a region predominantly containing one category of hydrocarbons, such as liquid hydrocarbons, 11 and a region predominantly containing a different category of hydrocarbons, such as gas, or the like.
  • the condition change may comprise a change in a material property, such as pressure, porosity, temperature, density, bulk modulus, chemistry, or the like.
  • the apparatus may further comprise a signal generator adapted to generate a signal to be emitted.
  • a relative distance between the apparatus and a subterranean interface may be determined from a single characteristic of the reflected signal. Alternatively, a plurality of characteristics of the reflected signal may be utilised.
  • a relative distance between the apparatus and a subterranean interface may be determined from a time of flight characteristic or measurement of the signal.
  • the time of flight characteristic may be defined by a time period between emission of the signal from the emitter and reception by the receiver.
  • the time of flight may be used directly as an output of the apparatus, wherein the relative distance is determined or outputted in terms of, or as a function of, the time of flight.
  • This arrangement may be advantageous in a comparative analysis with other distance measurements which are also based on time of flight measurements, In this way, a relative difference in, for example, two time of flight measurements may represent a proportional relative difference in distance. This arrangement may be utilised to eliminate or minimise errors due to inaccurate assumptions, measurements or the like of the propagation speed of a signal, particularly where signals are propagated through identical or similar materials.
  • the relative distance may be directly determined based on the time of flight measurement and the propagation speed of the signal.
  • the propagation speed of the signal may be estimated or directly measured or determined, for example.
  • the signal may comprise a wave based signal.
  • the signal may comprise a single frequency.
  • the signal may comprise a plurality of frequencies, which frequencies may be discrete. At least two of the plurality of frequencies may be emitted simultaneously. At least two of the plurality of frequencies may be emitted sequentially, with or without a temporal overlap.
  • a time of flight measurement may be determined by a phase offset of at least two frequencies within the signal received by the receiver.
  • a method of measuring time of flight using a phase off-set between two frequencies in a signal is disclosed in the present applicant's application no GB 0808189 5
  • the signal may comprise a pre-designed signal have predetermined properties, such as predetermined frequency, amplitude, phase or the like properties
  • the signal may be pre-designed in accordance with known or estimated subterranean conditions, such as dimensions, material types, material properties, chemical properties or the like, or any suitable combination thereof
  • the signal may comprise at least one frequency which is selected in accordance with a dimension, known or estimated, of the subterranean interface
  • the frequency may be selected such that the wavelength is greater than the expected thickness of an interface
  • the wavelength may be greater, in meters, than, for example, 0 25m, 0 5m, 1 m, 2m, 3m, 5m, 10m, 20m, 50m, 100m, etc, or any number therebetween
  • the signal may comprise a plurality or a range of frequencies to identify interfaces of differing thicknesses
  • the signal may comprise at least one frequency which is selected in accordance with a prior knowledge of the propagation speed of the signal in an associated subterranean environment
  • the signal may comprise at least one frequency selected in accordance with an approximation or estimation of the propagation speed of the signal in an associated subterranean environment
  • the signal may comprise at least one frequency selected in accordance with no prior knowledge or estimation of the propagation speed of the signal in an associated subterranean environment
  • the signal may comprise at least one frequency selected in accordance with resonant conditions of a subterranean environment
  • the apparatus may be adapted to emit a single signal Alternatively, the apparatus may be adapted to emit a plurality of signals The plurality of signals may be emitted simultaneously, temporally overlapping and/or consecutively The plurality of signals may be emitted in a single direction. Alternatively, the plurality of signals may be emitted in a plurality of directions.
  • the signal emitter may be adapted to emit one or a plurality of signals.
  • the apparatus may comprise a plurality of signal emitters, wherein each signal emitter is adapted to emit one or a plurality of signals.
  • the signal emitter may be adapted or configured for beamforming, for example using a phased-array antenna.
  • the apparatus may be configured to determine a shape of a subterranean interface. This may be achieved by directing one or more signals towards different subterranean regions.
  • the apparatus may be adapted to determine a relative distance between the apparatus and a plurality of interfaces. This arrangement may permit the apparatus to be appropriately positioned, translated, maintained or the like at a desired position between a plurality of interfaces.
  • the apparatus may be configured to emit a pair of signals.
  • the pair of signals may be emitted in any desired direction, such as the same or different directions. In one arrangement the pair of signals may be emitted in opposing directions.
  • the apparatus may be configured to emit a plurality of pairs of signals.
  • the apparatus may be configured to permit the relative distance between the apparatus and the interface to be determined in accordance with a difference in the time of flight of a pair of signals.
  • the apparatus may be configured to receive a reflected signal from a further apparatus.
  • the apparatus may be configured to emit a signal for reflection with an interface and for receipt by a further apparatus.
  • These arrangements may permit multiple apparatuses to be configured for communication to provide information about the time of emission/receipt of respective emitted signal. This may provide for an indication of the relative distance between the apparatuses and an interface.
  • the apparatus may be configured to emit identifiable signals, for example uniquely identifiable signals, such as signals of a particular frequency or modulation.
  • the apparatus may be configured to identify a reflected signal based upon its reflected frequency or modulation. Pairs of signals may be provided with the same or similar identifiers.
  • the signal may be emitted continuously, or from time to time, (periodically, aperiodically or the like), such as by second, by minute, hourly, daily, weekly, monthly, etc.
  • One or more characteristics of the reflected signal may be used to determine a condition of the interface, surrounding region, or the like.
  • characteristics of the reflected signal may be used to determine material properties, such as type, temperature, pressure, porosity, chemical conditions, and the like.
  • the apparatus may be configured to provide an output in accordance with a determination of a relative distance between the apparatus and a subterranean interface.
  • the output may be provided in the form of a monitoring signal.
  • the monitoring signal may be communicated to a local or remote location, such as a downhole location, surface location or the like.
  • the monitoring signal may be configured for wired communication, wireless communication, optical communication, acoustic communication (e.g. mud pulse) or the like, or any suitable combination thereof.
  • the apparatus may be configured to provide an output in the form of a monitoring signal when a signal characteristic, such as time of flight is less or more than a predetermined threshold.
  • a monitoring signal may be provided when the apparatus evaluates that a signal characteristic is indicative that the apparatus is too close to, or too far from a subterranean interface.
  • a monitoring signal may be provided (e.g. continuously/periodically provided) as an indication a signal characteristic to allow an operator to establish if the apparatus is too close to, or too far from a subterranean interface.
  • the downhole apparatus may be utilised to permit or assist control of a downhole activity, assembly or the like which may be affected or influenced by the relative location of a subterranean interface, such as well bore drilling operations, production operations or the like. Providing an accurate determination of the relative location of a subterranean interface may thus improve the control, operation or efficiency of the downhole activity, assembly or the like.
  • An output relative distance determination from the apparatus may be used directly to control a downhole activity, assembly or the like.
  • an output from the apparatus may be used indirectly to control a downhole activity, assembly or the like.
  • the output may be communicated to an operator to subsequently control or otherwise intervene in or with the downhole activity, assembly or the like.
  • the apparatus may be adapted to be translated along a subterranean path.
  • the apparatus may be configured to identify and or monitor the relative distance between the apparatus and the interface while said apparatus is being translated.
  • the relative distance between the apparatus and an interface may be utilised to dictate the direction of the apparatus along the subterranean path. For example, it may be advantageous for the apparatus to be advanced along a path which is maintained a desired distance or range from a subterranean interface.
  • the apparatus may be adapted to be mounted on or form part of a drilling assembly for use in drilling a bore, such as a bore extending between surface level and a subterranean reservoir, such as a hydrocarbon bearing reservoir.
  • the apparatus may be configured to determine a relative distance between the apparatus and a subterranean interface while a bore is being drilled by an associated drilling assembly.
  • the relative distance of the interface determined by the apparatus may be utilised to control the direction of the drilling assembly. Control may be achieved directly, for example by direct communication between the apparatus and the drilling assembly, or indirectly, for example via surface equipment, an operator or the like.
  • utilising the downhole apparatus to control the direction of drilling in this manner may permit the drilling assembly to form a bore which is positioned an optimum or desired distance from a subterranean interface, such as an interface between a layer of water and a layer of hydrocarbons.
  • the apparatus of the present invention may permit a bore to be drilled which optimally extends through a hydrocarbon bearing region.
  • the apparatus may be configured to provide an output in the form of a monitoring signal for directional correction or modification of a drilling assembly when one reflected signal is received after a particular threshold of time from another signal.
  • the monitoring signal may indicate which direction a drilling assembly should adopt.
  • the rate of change of the difference between two reflected signals may provide for the rate of change of direction of a drilling assembly (i.e. the quicker that the time between the received reflected signals increases being indicative of the drilling assembly coming quickly closer to one particular interface).
  • the apparatus may be adapted to be located at a fixed downhole location. In this way the apparatus may be adapted to determine a relative distance between the fixed location and a subterranean interface. The apparatus may also be adapted to monitor any changes in the relative distance between the fixed location and a subterranean interface.
  • the apparatus may be adapted to be located within a production zone within a production well bore.
  • the apparatus may be adapted to identify and monitor the location of an interface, such as a water/hydrocarbon interface. This may permit intervention within a production zone in the event of encroachment of such an interface into said zone.
  • zonal isolation may be performed, such as using packers, valve arrangement, well-kill fluids or the like.
  • the signal may comprise an acoustic signal.
  • the signal may comprise an electromagnetic signal.
  • the method may be used to ensure that a desired location of the apparatus, and any associated apparatus or equipment, relative to a subterranean interface is achieved and/or maintained
  • the method may comprise the step of controlling a downhole activity, assembly or the like based on the identified relative location of a subterranean interface
  • the method may comprise the step of controlling a drilling assembly to form a bore which is positioned at a desired distance from a subterranean interface, such as an interface between a layer of water and a layer of hydrocarbons
  • the method may permit a bore to be drilled which optimally extends through a hydrocarbon bearing region
  • the method may comprise the step of monitoring the location of a subterranean interface relative to a fixed downhole location
  • the downhole location may comprise a production zone
  • the method may comprise the step of identifying encroachment of an interface, such as a hydrocarbon/water interface, into or near the fixed downhole location
  • the method according to the second aspect may comprise use of the downhole apparatus according to the first aspect, and as such features and indications of use of the downhole apparatus defined above may be assumed compatible with and part of the method according to this second aspect.
  • an directional drilling apparatus comprising:
  • steerable drilling assembly is controlled in accordance with an output from the downhole apparatus.
  • a method according to a fourth aspect of the invention relates to the use of the apparatus of the third aspect.
  • a apparatus for controlling production from a subterranean reservoir comprising:
  • a production conduit arranged to be in fluid communication with a subterranean reservoir at a production zone;
  • a downhole apparatus configured for identifying advancement of a subterranean interface towards the production zone;
  • an isolation arrangement adapted to be activated to isolate fluid communication between the production conduit and the subterranean formation when the subterranean interface reaches a predetermined distance from the production zone.
  • a method according to a sixth aspect of the present invention relates to the use of the apparatus according to the fifth aspect.
  • the invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. It will be appreciated that one or more embodiments/aspects may be useful in downhole environments.
  • the above summary is intended to be merely exemplary and non-limiting.
  • Figure 1 is a diagrammatic representation of a downhole apparatus in accordance with an embodiment of the present invention
  • Figure 2 is a diagrammatic representation of a downhole use of the apparatus of Figure 1 , in accordance with an embodiment of the present invention
  • Figure 3 shows a plot of emission/receipt of interface signals and reflected interface signals
  • Figure 4 is a diagrammatic representation of a downhole apparatus in accordance with a further embodiment of the present invention.
  • Figure 5 is a diagrammatic representation of a downhole use of the apparatus of Figure 4, in accordance with an embodiment of the present invention
  • Figure 6 is a diagrammatic representation of a downhole apparatus in accordance with a further embodiment of the present invention.
  • Figure 7 shows a plot of emission/receipt of interface signals and reflected interface signals from the apparatus of Figure 6;
  • Figure 8 is a diagrammatic representation of a downhole use of the apparatus of Figure 4, in accordance with an embodiment of the present invention.
  • Figure 9 is a diagrammatic representation of a downhole apparatus according to a further embodiment of the present invention.
  • Figure 10 is a diagrammatic representation of a downhole use of the apparatus of Figure 9, in accordance with an embodiment of the present invention.
  • Figure 1 1 shows a flowchart of a method identifying relative position of subterranean or formation interface(s).
  • FIG. 1 shows a downhole apparatus, generally identified by reference numeral 100, in accordance with an embodiment of the present invention.
  • the apparatus comprises a signal emitter 110 and a signal receiver 120 (e.g. transducers for emitting/receiving signals, such as acoustic signals).
  • the apparatus 100 further comprises a processor 130 and memory 140, configured in a known manner, and in communication with the emitter 110 and receiver 120 (e.g. using a field programmable gate array, application specific integrated circuit, programmable intelligent computer, etc.).
  • the apparatus 100 is configured to emit a signal 115 from the emitter 110.
  • the signal 115 is an acoustic signal.
  • the signal is used to determine a feature, such as the relative location, of a subterranean interface.
  • the signal will hereinafter be referred to as an interface signal 115.
  • the apparatus 100 is configured to listen for a reflected interface signal 125, reflected from an interface (e.g. and interface provided by layers of oil/water, oil/gas, gas/water, etc.) by using the receiver 120/processor 130.
  • the processor 130/memory 140 are configured to identify the time taken for an interface signal 115, emitted by the signal emitter 110, to be received by the signal receiver 120 as a reflected interface signal 125 (i.e. the time of flight of the interface signal 115/reflected interface signal 125).
  • the apparatus 100 is configured to emit interface signals 115 periodically, such as every second, minute, hour, day, etc., although in alternative embodiments that need not be the case.
  • FIG. 2a is a diagrammatic representation of an exemplary use of the apparatus 100.
  • the apparatus 100 is mounted within, on or relative to a production tubing string 145 located within a drilled subterranean well bore 150.
  • the well bore 150 is an open bore, but in other arrangements the bore may be cased, lined or the like
  • the well bore 150 and production string 145 extend into a subterranean formation or reservoir which contains a layer of hydrocarbons 160 and a layer of water 165
  • the hydrocarbon and water layers 160, 165 are separated by an interface 170
  • the interface 170 is illustrated in Figure 2a as a well defined line of material change However, this is for convenience and clarity of the present description, and it should be understood that the interface 170 may be defined by a gradual material change
  • the production tubing string 145 is configured to communicate with the layer of hydrocarbons 160, in this case via ports 185, such that hydrocarbons may enter the production tubing 145, as indicated by arrows 190, to be produced to the surface
  • the region of communication may be termed a production zone 195
  • the apparatus 100 emits the interface signal 115 and due to a material change at the interface 170, at least a portion of the interface signal is reflected back as the reflected signal 125 Reflection may be caused by a change in density or the like, which establishes an impedance change in the subterranean environment
  • the apparatus 100 is configured to evaluate the time taken for the interface signal 115 to be reflected and received ( ⁇ e , time of flight) This time of flight evaluation can then be provided in order to identify and monitor the relative distance of the apparatus 100 from the interface 170
  • the apparatus 100 provides the ability to monitor the level and location of the interface 170, such that approach of the interface 170 towards or encroachment into the production zone 195 may be readily identified.
  • This monitoring capability therefore permits appropriate action to be taken to isolate the production zone 195 from the production string 145, which in the present embodiment is illustrated by closing the ports 185 by one or more isolation members 196.
  • Alternative zonal isolation may be achieved using packers, such as mechanical, inflatable, swellable packers or the like, well kill fluids or the like.
  • the apparatus 100 may be configured to communicate, for example via a monitoring signal, to a surface location, for example a surface apparatus, operator or the like.
  • the apparatus may be configured to communicate directly with a downhole assembly, apparatus or the like, such as an isolation apparatus. This may permit complete downhole monitoring and control of the production zone 195.
  • the monitoring signal may be communicated via a wired or wireless communication methods.
  • Figure 3a shows the emission of the interface signal 115 from the signal emitter 110, and the reflected interface signal 125 received at the signal receiver 120 for the downhole environment conditions shown in Figure 2a.
  • the time, t1 is indicative of the relative distance between the apparatus 100 and the interface 170.
  • Figure 3b shows the emission of the interface signal 115 from the signal emitter 110 after the interface 170 has moved (as shown in Figure 2b) and the reflected interface signal 125 received at the signal receiver 120.
  • the time t2 is indicative of the relative distance between the apparatus 100 and the interface 170.
  • steps may be initiated to isolate the production string 145 from the production zone 195.
  • the apparatus 100 is configured to provide an interface signal 1 15 at periodic intervals (such as by second, minute, hourly, daily, weekly, monthly, etc.), the apparatus 100 may be configured to provide an interface signal 1 15 at aperiodic intervals.
  • the monitoring signal is provided as a function only of the time taken to emit/receive the interface signal 1 15/reflected interface signal 125 (i.e. t1 , t2), in alternative embodiments the monitoring signal may be a function of the material characteristic to which the apparatus 100 is in communication with in the downhole environment (i.e. speed of transmission of signal in the medium).
  • the material characteristics may be provided by an operator (e.g. used at the surface, or provided via the wireline to the apparatus 100, pre-programmed on the apparatus 100, etc.) or may be determined from a sensor at the apparatus 100 (e.g. a sensor for determining bulk modulus, density, elasticity, etc.).
  • the apparatus 100 may be able to provide a ranging/distance of the interface 175 from the apparatus 100 based on the speed of sound in the proximate material and the time of flight, t1 , t2.
  • the interface 17o may be provided by a gradual variation in material (i.e. gradual variation in density or the like) over a range (e.g. 0.5 meters, 1 meter, 2 meters, etc.).
  • the apparatus 100 may be configured to provide an interface signal 115 of a particular frequency (or to provide a bandwidth of frequencies, which may comprise discrete frequencies) so as to accommodate the variation.
  • a number of discrete frequencies may be emitted (e g 14 Hz, 28 Hz, 70 Hz, 700 Hz) which correspond to particular interface depths (50 m, 25 m, 10 m, 1 m) in order to identify the interface
  • the apparatus 100 may be configured to be releasably attached at a particular location (e g the apparatus 100 may be detachably mountable on completion casing, etc ),
  • a particular apparatus 100 may be configured to provide an interface signal 115, reflected via an interface 170, to a further apparatus 100 for receipt of the reflected interface signal 125, and thus indication of the relative distance between the apparatus 100 and the interface 170
  • the first apparatus may be in communication with the second apparatus to provide/receive information regarding the time of emission/receipt of interface s ⁇ gnal(s) 115/reflected interface s ⁇ gnal(s) 125
  • FIG 4 shows a further embodiment of a downhole apparatus, generally identified by reference numeral 200, according to the present invention
  • the apparatus 200 comprises a combined signal emitter/receiver 210 ( ⁇ e a transceiver
  • the apparatus 200 further comprises a processor 230 and memory 240, in a similar manner to above, in communication with the emitter/receiver 210
  • FIG. 5a shows an exemplary downhole use of the apparatus 200, wherein the apparatus 200 is mounted on a steerable drilling assembly 290.
  • the drilling assembly 290 is configured to drill a bore 250 which extends through a hydrocarbon- bearing formation which includes a layer of hydrocarbons 270 and a layer of water 280.
  • an interface 275 exists at the boundary region between the hydrocarbon layer 270 and the water layer 280.
  • the interface 275 is approximated by a curvilinear representation. Again, it will be appreciated that the interface 275 may extend to a depth (and/or may be defined by a boundary region provided by water/oil occupying the same porous formation).
  • the drilling assembly 290 advances the bore
  • the apparatus 200 is configured to determine the time of flight of an interface signal 215/reflected interface signal 225 (in a similar manner to that described in the embodiment above) so as to provide for monitoring of the relative distance between the apparatus 200 and hydrocarbon/water interface 275.
  • the apparatus 200 is configured to provide a monitoring signal to the drilling assembly 290, which is used by the drilling assembly 290 to adapt the direction (e.g. inclination, etc.) of the bore (i.e. depending on the time of flight of the interface signal 215/reflected interface signal 225).
  • a monitoring signal to the drilling assembly 290, which is used by the drilling assembly 290 to adapt the direction (e.g. inclination, etc.) of the bore (i.e. depending on the time of flight of the interface signal 215/reflected interface signal 225).
  • the rate of change of time of flight may provide for the rate of change of interface 275 with respect to the advancement of the drilling assembly 290.
  • the actual distance may be determined by providing/estimating/approximating the speed of sound in the hydrocarbon layer 260.
  • the apparatus 100 is configured to allow the drilling assembly 290 to maintain a particular (e.g. constant/roughly constant) distance between the apparatus 200/drilling assembly 290 and the interface 275.
  • the apparatus 200/drilling assembly 290 can be configured such that the time of flight, t2, in Figure 3b, should be modified such that it remains the same/similar to that the time of flight, t1 , in Figure 3a (i e the direction of the drilling assembly is modified based on whether a subsequent time of flight is less than or more than a previous time of flight evaluation)
  • the drilling assembly 290 is configured to self- correct using the monitoring signal/time of flight ( ⁇ e to modify the direction of the drilling assembly 290 without other input), in other embodiments, the monitoring signal/time of flight may be provided to a surface operator or equipment to allow for correction or control of the drilling assembly 290
  • Figure 6 shows a further embodiment of a downhole apparatus, generally identified by reference numeral 300, according to the present invention
  • the apparatus 300 comprises first and second emitters/receivers 310a, 310b ( ⁇ e two transceivers 310a, 310b), configured to emit/receive interface s ⁇ gnal(s) 315a, 315b/reflected interface s ⁇ gnal(s) 325a, 325b
  • the apparatus 300 further comprises a processor 330 and memory 340, in a similar manner to above
  • the first and the second emitter/receiver 310a, 310b are disposed either side of the apparatus 300 ( ⁇ e so as to provide for emission of an interface signal 315a, 315b in opposite directions) It will be appreciated that the emitter/receiver 310 may not be provided on either side, but may be configured to provide directional interface signals 315a, 315b, and thus have the same effect
  • the processor 330/memory 340 are configured to identify the time taken for the interface signal 315 to be received as a reflected interface signal 325 (time of flight) for each emitter/receiver 310a, 310b
  • the apparatus 300 is configured to provide for identification of the relative distance between the apparatus 300 and particular formation ⁇ nterface(s) based on difference in time from emitting and receiving respective interface signals 315a, 315b/reflected interface signals 325a, 325b from the respective first and second emitter/receiver 310a, 310b
  • Figures 7a and 7b show exemplary emissions of interface signals 315a, 315b from the first and second emitter/receiver 310a, 310b respectively, as well as the respective reflected interface signals 325a, 325b received.
  • the time, tD1 is indicative of the relative distance between the apparatus 300 and a first interface.
  • the time, tD2 is indicative of the relative distance between the apparatus 300 and a second interface.
  • the time, t3, is indicative of the relative difference between the distances.
  • Figures 8a and 8b show an exemplary use of the apparatus 300, provided in combination with a steerable drilling assembly 390.
  • the drilling assembly 290 is configured to drill a bore 350 which extends through a hydrocarbon-bearing formation which includes an intermediate layer of liquid hydrocarbons 370, a lower layer of water 380a and an upper layer of gaseous hydrocarbons 380b.
  • An interface 375a exists between the liquid hydrocarbon layer 370 and the water layer 380a, and an interface 275b exists between the liquid hydrocarbon layer 370 and the gas layer 380b.
  • Each interface 375a, 375a is approximated by a curvilinear representation. Again, it will be appreciated that each interface 375a, 375b may extend to a depth, and/or may be defined by a boundary region provided by water/oil/gas occupying the same porous formation.
  • the drilling assembly 390 advances a bore 350.
  • the apparatus 300 is configured to determine the difference, t3, in the time of flight between the first and second interface signal 315a, 315b/reflected interface signal
  • the apparatus 300 is configured to provide a monitoring signal to the drilling assembly 390, to allow the drilling assembly 390 to adapt the direction (e.g. inclination, etc.) of the bore 350 depending on the time t3 so as to maintain the drilling assembly 390 (and thus the bore) roughly equidistant between the first and second interfaces 375a, 375b (as shown by D1 , D2, in Figure 8b) and suitably within the layer of liquid hydrocarbons 370. That is to say that the apparatus 300/drilling assembly 390 are configured to try to reduce t3 to zero/roughly zero.
  • the rate of change of time, dt3/dt provides for the rate of change of interface
  • the actual distance may be determined by providing/estimating/approximating the speed of sound in the hydrocarbon bearing formation 370.
  • the drilling assembly 390 is configured to self- correct using the monitoring signal/difference in time of flight, t3, in other embodiments, the monitoring signal/difference in time of flight, t3, may be provided to a surface operator or equipment to allow for correction of the drilling assembly 390.
  • the apparatus 300 of Figure 6 may be provided by two apparatus 100, 200 of Figure 1 and/or 4. In some embodiments, more than two apparatus 100, 200, 300 may be provided in order to provide for identifying the relative distance to interface(s).
  • FIG. 9 shows a further embodiment of a downhole apparatus, generally indicated by reference numeral 400, according to the present invention.
  • the apparatus 400 comprises a plurality of emitters/receivers 410 (i.e. transceivers 410) configured to emit/receive interface signal(s) 415/reflected interface signal(s) 425 in a plurality of directions (not all shown for clarity).
  • the apparatus 400 further comprises a processor 430 and memory 440, in a similar manner to above, in communication with the emitters/receivers 410.
  • the emitter/receivers 410 are disposed peripherally around the apparatus 400 (i.e. so as to provide for emission of an interface signal in a plurality of differing directions).
  • the emitter/receivers 410 are disposed peripherally around the apparatus 400 such that a particular emitter/receiver 410 has a corresponding emitter/receiver 410 disposed in an opposite sense.
  • the apparatus 400 is configured such that each emitter/receiver 410 emits an identifiable interface signal 415 (i.e. by modulating the interface signal 310 to have a unique identifier, such as by amplitude modulation, phase-shift keying, etc of the emitted interface signal 415)
  • the apparatus 400/processor 430 is configured to identify a particular reflected interface signal 425 based on the unique identifier modulated in the reflected interface signal 425 That is to say that irrespective of the number of emitter/receivers 410, the apparatus 400 is able to determine the time of flight of particular interface signals 415/reflected interfaces signals 425 at a particular emitter/receiver 410 ( ⁇ e to prevent/avoid/reduce the chance of interference of signals)
  • Figure 10a shows the apparatus 400 provided with a drilling assembly 490 for drilling a bore 450 which extends through a hydrocarbon-bearing formation which includes an intermediate layer of liquid hydrocarbons 470, a lower layer of water 480a and an upper layer of gaseous hydrocarbons 480b, in a similar manner to that described above, in which respective interfaces 475a, 475b exist
  • each interface 475a 475a may extend to a depth, and/or may be defined by a boundary region provided by water/oil/gas occupying the same porous formation
  • Figure 10b shows a cross-section at P-P in Figure 10a
  • the interfaces 475a, 475b as not simply curvilinear in a two dimensional manner, but provide a curved/irregular planer interface
  • the drilling assembly 490 advances a bore 450
  • the apparatus 400 is configured to determine the difference in the time of flight between opposing emitters/receivers 410 so as to provide for monitoring/identifying the relative distance between the apparatus 300 and hydrocarbon/water/gas interface 375a, 375b
  • the apparatus is configured to determine the difference in time of flight between each pair of respective emitters/receivers 410 (e g measure signals K1 and K2 so as to provide for identification of the relative distance of em ⁇ tter/rece ⁇ ver-K1/K2 and respective interfaces 475a, 475b and signals L1 and L2 so as to provide for identification of the relative distance of em ⁇ tter/rece ⁇ ver-L1/L2 and respective interfaces 475a, 475b)
  • the apparatus 400 is configured to provide a monitoring signal to the drilling assembly 490, to allow the drilling assembly 490 to adapt the direction (e g inclination, etc ) of the bore 450 depending on each of the respective time of flight evaluations and therefore maintaining the drilling assembly 490 (and thus the bore) roughly equidistant between the first and second planer interfaces 475a, 475b
  • the drilling assembly 490 is configured to self-correct, in other embodiments, the monitoring signal/difference in time of flight may be provided to a surface operator or equipment to allow for correction of the drilling assembly 490
  • the emitters/receivers 410 may not be used as pairs, but may be used individually, or may be used in groups more than two, such as three, four, six, etc.
  • the emitters/receiver may be provided by one, or more directional emitters/receivers (e g beamforming)
  • each interface signal has been described as modulated, in other embodiments, each signal may be spaced by time (e g provided in a particular window), such as by using time division multiple access (TDMA)
  • each or some emitters/receiver 410 may be configured to emit at a particular time division ( ⁇ e an interface signal being emitted during a particular window)
  • FIG 11 shows a flowchart 500 of a method of identifying the relative position of formation ⁇ nterface(s)
  • These interface signals are received, indicted by step 520 as reflected interface s ⁇ gnal(s) at the apparatus
  • the reflected interface s ⁇ gnal(s) have been reflected from particular formation ⁇ nterface(s) in a downhole environment (e.g. between oil/water interface).
  • a step 530 is then performed for identification of the relative distance between the apparatus and particular formation interface(s) based on characteristics of reflected interface signal(s).
  • the characteristics may be based on the time of flight of a particular interface signal/reflected interface signal (or plurality of interface signals/reflected interface signals). The characteristics may be based on the difference between two (or more) time of flight evaluations of particular interface signal/reflected interface signal (or plurality of interface signals/reflected interface signals).
  • the method comprises providing for correction of the direction of a drill bit or drilling assembly or the like using the characteristics of reflected interface signal(s) based upon the relative distance between the apparatus and particular formation interface(s).
  • the method comprises providing for monitoring of a level of a formation interface in a downhole environment based upon the relative distance between the apparatus and particular formation interface(s) by using characteristics of reflected interface signal(s).
  • 150, 250, 350, 450 may extend in any number of directions, and are not limited to those described.

Abstract

There is described downhole apparatus (100) and methods for identifying the position of an interface (170) within a subterranean formation. In some examples, the apparatus is for use at a fixed downhole location, such as a production zone (195), and is configured to determine the encroachment of an interface (e.g. water) into the production zone. In other examples, the apparatus is for use with a drill assembly (290) and is configured to determine the distance of a drill assembly from a subterranean interface during drilling. In some examples, the apparatus uses signals comprising a plurality of frequencies, which may be selected based on the particular subterranean interfaces being measured.

Description

DOWNHOLE APPARATUS AND METHOD
FIELD OF THE INVENTION
The present invention relates to a downhole apparatus and method, and in particular to a downhole apparatus and method for determining the position of an interface within a subterranean formation.
BACKGROUND TO THE INVENTION
In the oil and gas exploration and production industry, geological investigations are performed to determine, as accurately as possible, the presence and location of subterranean hydrocarbon bearing formations or reservoirs. The geological investigations may utilise seismic techniques, typically involving initiating explosions at surface level and analysing the reflections of these explosions from the earth to develop an estimation of the geological make-up of the region under investigation. Regions of interest may be further explored by drilling investigatory bores and taking geological samples for subsequent analysis, for example.
Following a successful geological exploration, one or more well bores are drilled in the earth, often extending thousands of feet, to intercept the identified reservoirs and provide a path to produce the hydrocarbons to surface. Conventionally, the wellbores are drilled using a drill string formed by a drill bit mounted on the end of a tubing string of drill pipes and collars.
Once the well bore is drilled to the required depth, the bore is completed by running in a production tubing string which extends between the surface and the reservoir. The production tubing string is arranged to be in fluid communication with the reservoir at one or more desired locations. The locations of fluid communication are typically called production zones.
A hydrocarbon bearing formation normally contains both hydrocarbon liquids and gases, and will invariably also contain water. 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 liquid hydrocarbons and a lower layer of formation water, with respective interfaces therebetween
Significant efforts are made to minimise the volume of formation 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 establish production zones in regions where the possibility of water production is minimised This requires the well bores to extend through and follow or track the layers of hydrocarbons as accurately as possible
The data produced from geological exploration surveys may be used to determine a desired path of the drill string, for example to avoid regions with large volumes of formation water However, it is understood in the art that the accuracy and sophistication of the data from existing seismic techniques may be insufficient to ensure that an optimum course of a drilled well bore is achieved
Furthermore, movement of the interfaces between the different layers in a formation occurs over the course of time as the hydrocarbons are produced, 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 SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a downhole apparatus for identifying the position of an interface within a subterranean formation, said apparatus comprising a signal emitter configured to emit a signal; and
a signal receiver configured to receive the signal following reflection from a subterranean interface,
wherein a relative distance between the apparatus and the subterranean interface is determined from a characteristic of the reflected signal.
Accordingly, the downhole apparatus of the present invention may permit a downhole assessment of the relative location of a subterranean interface. The apparatus may permit initial identification of the interface, monitoring of the interface or the like.
The apparatus may be configured for use in ensuring that a desired location of the apparatus, and any associated apparatus or equipment, relative to a subterranean interface is achieved and/or maintained.
The subterranean interface may be defined by a condition change within a subterranean environment. The condition change may comprise a material change. The condition change may comprise a bulk material change, such as a change from one geological type or structure to another, or a change or variance in a material which is held within a subterranean structure, such as a porous structure, or otherwise. The interface may be defined between a region predominantly containing water and a region predominantly containing hydrocarbons. The interface may be defined between a region predominantly containing one category of hydrocarbons, such as liquid hydrocarbons,11 and a region predominantly containing a different category of hydrocarbons, such as gas, or the like.
The condition change may comprise a change in a material property, such as pressure, porosity, temperature, density, bulk modulus, chemistry, or the like.
The apparatus may further comprise a signal generator adapted to generate a signal to be emitted. A relative distance between the apparatus and a subterranean interface may be determined from a single characteristic of the reflected signal. Alternatively, a plurality of characteristics of the reflected signal may be utilised.
A relative distance between the apparatus and a subterranean interface may be determined from a time of flight characteristic or measurement of the signal. The time of flight characteristic may be defined by a time period between emission of the signal from the emitter and reception by the receiver. The time of flight may be used directly as an output of the apparatus, wherein the relative distance is determined or outputted in terms of, or as a function of, the time of flight. This arrangement may be advantageous in a comparative analysis with other distance measurements which are also based on time of flight measurements, In this way, a relative difference in, for example, two time of flight measurements may represent a proportional relative difference in distance. This arrangement may be utilised to eliminate or minimise errors due to inaccurate assumptions, measurements or the like of the propagation speed of a signal, particularly where signals are propagated through identical or similar materials.
Alternatively, or additionally, the relative distance may be directly determined based on the time of flight measurement and the propagation speed of the signal. The propagation speed of the signal may be estimated or directly measured or determined, for example.
The signal may comprise a wave based signal. The signal may comprise a single frequency. Alternatively, the signal may comprise a plurality of frequencies, which frequencies may be discrete. At least two of the plurality of frequencies may be emitted simultaneously. At least two of the plurality of frequencies may be emitted sequentially, with or without a temporal overlap.
A time of flight measurement may be determined by a phase offset of at least two frequencies within the signal received by the receiver. A method of measuring time of flight using a phase off-set between two frequencies in a signal is disclosed in the present applicant's application no GB 0808189 5
The signal may comprise a pre-designed signal have predetermined properties, such as predetermined frequency, amplitude, phase or the like properties The signal may be pre-designed in accordance with known or estimated subterranean conditions, such as dimensions, material types, material properties, chemical properties or the like, or any suitable combination thereof
In one embodiment the signal may comprise at least one frequency which is selected in accordance with a dimension, known or estimated, of the subterranean interface The frequency may be selected such that the wavelength is greater than the expected thickness of an interface The wavelength may be greater, in meters, than, for example, 0 25m, 0 5m, 1 m, 2m, 3m, 5m, 10m, 20m, 50m, 100m, etc, or any number therebetween The signal may comprise a plurality or a range of frequencies to identify interfaces of differing thicknesses
The signal may comprise at least one frequency which is selected in accordance with a prior knowledge of the propagation speed of the signal in an associated subterranean environment The signal may comprise at least one frequency selected in accordance with an approximation or estimation of the propagation speed of the signal in an associated subterranean environment The signal may comprise at least one frequency selected in accordance with no prior knowledge or estimation of the propagation speed of the signal in an associated subterranean environment
The signal may comprise at least one frequency selected in accordance with resonant conditions of a subterranean environment
The apparatus may be adapted to emit a single signal Alternatively, the apparatus may be adapted to emit a plurality of signals The plurality of signals may be emitted simultaneously, temporally overlapping and/or consecutively The plurality of signals may be emitted in a single direction. Alternatively, the plurality of signals may be emitted in a plurality of directions.
The signal emitter may be adapted to emit one or a plurality of signals. The apparatus may comprise a plurality of signal emitters, wherein each signal emitter is adapted to emit one or a plurality of signals. The signal emitter may be adapted or configured for beamforming, for example using a phased-array antenna.
The apparatus may be configured to determine a shape of a subterranean interface. This may be achieved by directing one or more signals towards different subterranean regions.
The apparatus may be adapted to determine a relative distance between the apparatus and a plurality of interfaces. This arrangement may permit the apparatus to be appropriately positioned, translated, maintained or the like at a desired position between a plurality of interfaces.
The apparatus may be configured to emit a pair of signals. The pair of signals may be emitted in any desired direction, such as the same or different directions. In one arrangement the pair of signals may be emitted in opposing directions. The apparatus may be configured to emit a plurality of pairs of signals.
The apparatus may be configured to permit the relative distance between the apparatus and the interface to be determined in accordance with a difference in the time of flight of a pair of signals.
The apparatus may be configured to receive a reflected signal from a further apparatus. The apparatus may be configured to emit a signal for reflection with an interface and for receipt by a further apparatus. These arrangements may permit multiple apparatuses to be configured for communication to provide information about the time of emission/receipt of respective emitted signal. This may provide for an indication of the relative distance between the apparatuses and an interface.
The apparatus may be configured to emit identifiable signals, for example uniquely identifiable signals, such as signals of a particular frequency or modulation. The apparatus may be configured to identify a reflected signal based upon its reflected frequency or modulation. Pairs of signals may be provided with the same or similar identifiers.
The signal may be emitted continuously, or from time to time, (periodically, aperiodically or the like), such as by second, by minute, hourly, daily, weekly, monthly, etc.
One or more characteristics of the reflected signal may be used to determine a condition of the interface, surrounding region, or the like. For example, characteristics of the reflected signal may be used to determine material properties, such as type, temperature, pressure, porosity, chemical conditions, and the like.
The apparatus may be configured to provide an output in accordance with a determination of a relative distance between the apparatus and a subterranean interface. The output may be provided in the form of a monitoring signal. The monitoring signal may be communicated to a local or remote location, such as a downhole location, surface location or the like. The monitoring signal may be configured for wired communication, wireless communication, optical communication, acoustic communication (e.g. mud pulse) or the like, or any suitable combination thereof.
The apparatus may be configured to provide an output in the form of a monitoring signal when a signal characteristic, such as time of flight is less or more than a predetermined threshold. For example, a monitoring signal may be provided when the apparatus evaluates that a signal characteristic is indicative that the apparatus is too close to, or too far from a subterranean interface. A monitoring signal may be provided (e.g. continuously/periodically provided) as an indication a signal characteristic to allow an operator to establish if the apparatus is too close to, or too far from a subterranean interface.
The downhole apparatus may be utilised to permit or assist control of a downhole activity, assembly or the like which may be affected or influenced by the relative location of a subterranean interface, such as well bore drilling operations, production operations or the like. Providing an accurate determination of the relative location of a subterranean interface may thus improve the control, operation or efficiency of the downhole activity, assembly or the like.
An output relative distance determination from the apparatus may be used directly to control a downhole activity, assembly or the like. Alternatively, or additionally, an output from the apparatus may be used indirectly to control a downhole activity, assembly or the like. For example, the output may be communicated to an operator to subsequently control or otherwise intervene in or with the downhole activity, assembly or the like.
The apparatus may be adapted to be translated along a subterranean path. In this arrangement the apparatus may be configured to identify and or monitor the relative distance between the apparatus and the interface while said apparatus is being translated. The relative distance between the apparatus and an interface may be utilised to dictate the direction of the apparatus along the subterranean path. For example, it may be advantageous for the apparatus to be advanced along a path which is maintained a desired distance or range from a subterranean interface.
The apparatus may be adapted to be mounted on or form part of a drilling assembly for use in drilling a bore, such as a bore extending between surface level and a subterranean reservoir, such as a hydrocarbon bearing reservoir. In this arrangement the apparatus may be configured to determine a relative distance between the apparatus and a subterranean interface while a bore is being drilled by an associated drilling assembly. The relative distance of the interface determined by the apparatus may be utilised to control the direction of the drilling assembly. Control may be achieved directly, for example by direct communication between the apparatus and the drilling assembly, or indirectly, for example via surface equipment, an operator or the like. Utilising the downhole apparatus to control the direction of drilling in this manner may permit the drilling assembly to form a bore which is positioned an optimum or desired distance from a subterranean interface, such as an interface between a layer of water and a layer of hydrocarbons. The apparatus of the present invention may permit a bore to be drilled which optimally extends through a hydrocarbon bearing region.
The apparatus may be configured to provide an output in the form of a monitoring signal for directional correction or modification of a drilling assembly when one reflected signal is received after a particular threshold of time from another signal. The monitoring signal may indicate which direction a drilling assembly should adopt.
The rate of change of the difference between two reflected signals may provide for the rate of change of direction of a drilling assembly (i.e. the quicker that the time between the received reflected signals increases being indicative of the drilling assembly coming quickly closer to one particular interface).
The apparatus may be adapted to be located at a fixed downhole location. In this way the apparatus may be adapted to determine a relative distance between the fixed location and a subterranean interface. The apparatus may also be adapted to monitor any changes in the relative distance between the fixed location and a subterranean interface.
In one embodiment the apparatus may be adapted to be located within a production zone within a production well bore. In this arrangement the apparatus may be adapted to identify and monitor the location of an interface, such as a water/hydrocarbon interface. This may permit intervention within a production zone in the event of encroachment of such an interface into said zone. For example, zonal isolation may be performed, such as using packers, valve arrangement, well-kill fluids or the like.
The signal may comprise an acoustic signal. The signal may comprise an electromagnetic signal. According to a second aspect of the present invention there is provided a method of identifying the position of an interface within a subterranean formation, said method comprising the steps of
emitting a signal from a downhole apparatus,
receiving the signal at the downhole apparatus following reflection from a subterranean interface, and
determining a relative distance between the apparatus and the subterranean interface from a characteristic of the reflected signal
The method may be used to ensure that a desired location of the apparatus, and any associated apparatus or equipment, relative to a subterranean interface is achieved and/or maintained
A relative distance between the apparatus and a subterranean interface may be determined from a time of flight characteristic or measurement of the signal
The method may comprise the step of controlling a downhole activity, assembly or the like based on the identified relative location of a subterranean interface
The method may comprise the step of controlling a drilling assembly to form a bore which is positioned at a desired distance from a subterranean interface, such as an interface between a layer of water and a layer of hydrocarbons The method may permit a bore to be drilled which optimally extends through a hydrocarbon bearing region
The method may comprise the step of monitoring the location of a subterranean interface relative to a fixed downhole location The downhole location may comprise a production zone The method may comprise the step of identifying encroachment of an interface, such as a hydrocarbon/water interface, into or near the fixed downhole location
The method according to the second aspect may comprise use of the downhole apparatus according to the first aspect, and as such features and indications of use of the downhole apparatus defined above may be assumed compatible with and part of the method according to this second aspect.
According to a third aspect of the present invention there is provided an directional drilling apparatus, said apparatus comprising:
a steerable drilling assembly;
a downhole apparatus according to the first aspect,
wherein the steerable drilling assembly is controlled in accordance with an output from the downhole apparatus.
A method according to a fourth aspect of the invention relates to the use of the apparatus of the third aspect.
According to a fifth aspect of the present invention there is provided a apparatus for controlling production from a subterranean reservoir, said apparatus comprising:
a production conduit arranged to be in fluid communication with a subterranean reservoir at a production zone;
a downhole apparatus according to the first aspect and configured for identifying advancement of a subterranean interface towards the production zone; and
an isolation arrangement adapted to be activated to isolate fluid communication between the production conduit and the subterranean formation when the subterranean interface reaches a predetermined distance from the production zone.
A method according to a sixth aspect of the present invention relates to the use of the apparatus according to the fifth aspect.
The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. It will be appreciated that one or more embodiments/aspects may be useful in downhole environments. The above summary is intended to be merely exemplary and non-limiting.
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 a downhole apparatus in accordance with an embodiment of the present invention;
Figure 2 is a diagrammatic representation of a downhole use of the apparatus of Figure 1 , in accordance with an embodiment of the present invention;
Figure 3 shows a plot of emission/receipt of interface signals and reflected interface signals;
Figure 4 is a diagrammatic representation of a downhole apparatus in accordance with a further embodiment of the present invention;
Figure 5 is a diagrammatic representation of a downhole use of the apparatus of Figure 4, in accordance with an embodiment of the present invention;
Figure 6 is a diagrammatic representation of a downhole apparatus in accordance with a further embodiment of the present invention;
Figure 7 shows a plot of emission/receipt of interface signals and reflected interface signals from the apparatus of Figure 6;
Figure 8 is a diagrammatic representation of a downhole use of the apparatus of Figure 4, in accordance with an embodiment of the present invention;
Figure 9 is a diagrammatic representation of a downhole apparatus according to a further embodiment of the present invention;
Figure 10 is a diagrammatic representation of a downhole use of the apparatus of Figure 9, in accordance with an embodiment of the present invention; and
Figure 1 1 shows a flowchart of a method identifying relative position of subterranean or formation interface(s). DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows a downhole apparatus, generally identified by reference numeral 100, in accordance with an embodiment of the present invention. The apparatus comprises a signal emitter 110 and a signal receiver 120 (e.g. transducers for emitting/receiving signals, such as acoustic signals). The apparatus 100 further comprises a processor 130 and memory 140, configured in a known manner, and in communication with the emitter 110 and receiver 120 (e.g. using a field programmable gate array, application specific integrated circuit, programmable intelligent computer, etc.).
The apparatus 100 is configured to emit a signal 115 from the emitter 110. In the embodiment shown the signal 115 is an acoustic signal. As will be described below, the signal is used to determine a feature, such as the relative location, of a subterranean interface. Thus, for convenience of the present description, the signal will hereinafter be referred to as an interface signal 115. The apparatus 100 is configured to listen for a reflected interface signal 125, reflected from an interface (e.g. and interface provided by layers of oil/water, oil/gas, gas/water, etc.) by using the receiver 120/processor 130.
The processor 130/memory 140 are configured to identify the time taken for an interface signal 115, emitted by the signal emitter 110, to be received by the signal receiver 120 as a reflected interface signal 125 (i.e. the time of flight of the interface signal 115/reflected interface signal 125). In the present embodiment the apparatus 100 is configured to emit interface signals 115 periodically, such as every second, minute, hour, day, etc., although in alternative embodiments that need not be the case.
Figure 2a is a diagrammatic representation of an exemplary use of the apparatus 100. The apparatus 100 is mounted within, on or relative to a production tubing string 145 located within a drilled subterranean well bore 150. In the arrangement shown the well bore 150 is an open bore, but in other arrangements the bore may be cased, lined or the like The well bore 150 and production string 145 extend into a subterranean formation or reservoir which contains a layer of hydrocarbons 160 and a layer of water 165 The hydrocarbon and water layers 160, 165 are separated by an interface 170 The interface 170 is illustrated in Figure 2a as a well defined line of material change However, this is for convenience and clarity of the present description, and it should be understood that the interface 170 may be defined by a gradual material change
In a production operation, the production tubing string 145 is configured to communicate with the layer of hydrocarbons 160, in this case via ports 185, such that hydrocarbons may enter the production tubing 145, as indicated by arrows 190, to be produced to the surface The region of communication may be termed a production zone 195
The apparatus 100 emits the interface signal 115 and due to a material change at the interface 170, at least a portion of the interface signal is reflected back as the reflected signal 125 Reflection may be caused by a change in density or the like, which establishes an impedance change in the subterranean environment
The apparatus 100 is configured to evaluate the time taken for the interface signal 115 to be reflected and received (ι e , time of flight) This time of flight evaluation can then be provided in order to identify and monitor the relative distance of the apparatus 100 from the interface 170
With continued production, perhaps over the course of a number of months or years, the volume of hydrocarbons 160 contained within the formation will diminish, and a shift in the interface 170 will occur Such a shift in the location of the interface 170 is shown in Figure 2b, wherein the interface 170 has encroached into the production zone 195 This condition is undesirable in that water 165 will begin to be produced to the surface The disadvantages of producing water are well documented in the art The apparatus 100 provides the ability to monitor the level and location of the interface 170, such that approach of the interface 170 towards or encroachment into the production zone 195 may be readily identified. This monitoring capability therefore permits appropriate action to be taken to isolate the production zone 195 from the production string 145, which in the present embodiment is illustrated by closing the ports 185 by one or more isolation members 196. Alternative zonal isolation may be achieved using packers, such as mechanical, inflatable, swellable packers or the like, well kill fluids or the like.
The apparatus 100 may be configured to communicate, for example via a monitoring signal, to a surface location, for example a surface apparatus, operator or the like. Alternatively, the apparatus may be configured to communicate directly with a downhole assembly, apparatus or the like, such as an isolation apparatus. This may permit complete downhole monitoring and control of the production zone 195.
The monitoring signal may be communicated via a wired or wireless communication methods.
Figure 3a shows the emission of the interface signal 115 from the signal emitter 110, and the reflected interface signal 125 received at the signal receiver 120 for the downhole environment conditions shown in Figure 2a. The time, t1, is indicative of the relative distance between the apparatus 100 and the interface 170. Figure 3b shows the emission of the interface signal 115 from the signal emitter 110 after the interface 170 has moved (as shown in Figure 2b) and the reflected interface signal 125 received at the signal receiver 120. The time t2 is indicative of the relative distance between the apparatus 100 and the interface 170.
Therefore, when the time t2 is, for example, less than a predetermined threshold, steps may be initiated to isolate the production string 145 from the production zone 195.
Although the apparatus 100 is configured to provide an interface signal 1 15 at periodic intervals (such as by second, minute, hourly, daily, weekly, monthly, etc.), the apparatus 100 may be configured to provide an interface signal 1 15 at aperiodic intervals. Similarly, while in this embodiment, the monitoring signal is provided as a function only of the time taken to emit/receive the interface signal 1 15/reflected interface signal 125 (i.e. t1 , t2), in alternative embodiments the monitoring signal may be a function of the material characteristic to which the apparatus 100 is in communication with in the downhole environment (i.e. speed of transmission of signal in the medium).
In such embodiments, the material characteristics may be provided by an operator (e.g. used at the surface, or provided via the wireline to the apparatus 100, pre-programmed on the apparatus 100, etc.) or may be determined from a sensor at the apparatus 100 (e.g. a sensor for determining bulk modulus, density, elasticity, etc.). In such embodiments, the apparatus 100 may be able to provide a ranging/distance of the interface 175 from the apparatus 100 based on the speed of sound in the proximate material and the time of flight, t1 , t2.
As noted above, the interface 17o may be provided by a gradual variation in material (i.e. gradual variation in density or the like) over a range (e.g. 0.5 meters, 1 meter, 2 meters, etc.). In such arrangements, the apparatus 100 may be configured to provide an interface signal 115 of a particular frequency (or to provide a bandwidth of frequencies, which may comprise discrete frequencies) so as to accommodate the variation.
That is to say that the frequency of the interface signal 115 may be selected (i.e. depending upon the speed of sound in the subterranean environment) such that the wavelength of the interface signal 115 is longer than that of an expected interface 170. For example, if the speed of sound in a particular hydrocarbon-bearing formation were to be 700 m/s, it would be possible to evaluate a range of frequencies that would provide suitable wavelengths of 50 meters and less so as to accommodate a gradual variation in density of 50 meters or less (i.e. frequency = speed/wavelength). In such conditions, a number of discrete frequencies may be emitted (e g 14 Hz, 28 Hz, 70 Hz, 700 Hz) which correspond to particular interface depths (50 m, 25 m, 10 m, 1 m) in order to identify the interface
While in the above example, only one apparatus 100 was described, it will readily be appreciated than any number of apparatus 100 may be provided, which may extend along and/or around the production string 145 and/or well bore 150 Similarly, although the apparatus 100 has been described as being fixed, in other embodiments, that need not be the case, and in some embodiments, the apparatus 100 may be configured to be releasably attached at a particular location (e g the apparatus 100 may be detachably mountable on completion casing, etc ), In some embodiments, a particular apparatus 100 may be configured to provide an interface signal 115, reflected via an interface 170, to a further apparatus 100 for receipt of the reflected interface signal 125, and thus indication of the relative distance between the apparatus 100 and the interface 170 In such arrangements, the first apparatus may be in communication with the second apparatus to provide/receive information regarding the time of emission/receipt of interface sιgnal(s) 115/reflected interface sιgnal(s) 125
Figure 4 shows a further embodiment of a downhole apparatus, generally identified by reference numeral 200, according to the present invention The apparatus 200 comprises a combined signal emitter/receiver 210 (ι e a transceiver
210) The apparatus 200 further comprises a processor 230 and memory 240, in a similar manner to above, in communication with the emitter/receiver 210
Again, the apparatus 200 is configured to emit acoustically an interface signal 215 and to listen for a reflected interface signal 225, reflected from an interface Again, the processor 230/memory 240 are configured to identify the time taken for the interface signal 215 to be received as a reflected interface signal 225 (time of flight) Figure 5a shows an exemplary downhole use of the apparatus 200, wherein the apparatus 200 is mounted on a steerable drilling assembly 290. The drilling assembly 290 is configured to drill a bore 250 which extends through a hydrocarbon- bearing formation which includes a layer of hydrocarbons 270 and a layer of water 280.
As is shown in Figure 5a, an interface 275 exists at the boundary region between the hydrocarbon layer 270 and the water layer 280. The interface 275 is approximated by a curvilinear representation. Again, it will be appreciated that the interface 275 may extend to a depth (and/or may be defined by a boundary region provided by water/oil occupying the same porous formation).
In use (see Figures 5b and 5c), the drilling assembly 290 advances the bore
250. At a similar time, the apparatus 200 is configured to determine the time of flight of an interface signal 215/reflected interface signal 225 (in a similar manner to that described in the embodiment above) so as to provide for monitoring of the relative distance between the apparatus 200 and hydrocarbon/water interface 275.
The apparatus 200 is configured to provide a monitoring signal to the drilling assembly 290, which is used by the drilling assembly 290 to adapt the direction (e.g. inclination, etc.) of the bore (i.e. depending on the time of flight of the interface signal 215/reflected interface signal 225).
The rate of change of time of flight may provide for the rate of change of interface 275 with respect to the advancement of the drilling assembly 290. In a similar manner to above, the actual distance may be determined by providing/estimating/approximating the speed of sound in the hydrocarbon layer 260.
As shown in Figures 5b and 5c, the apparatus 100 is configured to allow the drilling assembly 290 to maintain a particular (e.g. constant/roughly constant) distance between the apparatus 200/drilling assembly 290 and the interface 275.
Referring again to Figure 3, it will be appreciated that the apparatus 200/drilling assembly 290 can be configured such that the time of flight, t2, in Figure 3b, should be modified such that it remains the same/similar to that the time of flight, t1 , in Figure 3a (i e the direction of the drilling assembly is modified based on whether a subsequent time of flight is less than or more than a previous time of flight evaluation)
Although in this embodiment the drilling assembly 290 is configured to self- correct using the monitoring signal/time of flight (ι e to modify the direction of the drilling assembly 290 without other input), in other embodiments, the monitoring signal/time of flight may be provided to a surface operator or equipment to allow for correction or control of the drilling assembly 290
Figure 6 shows a further embodiment of a downhole apparatus, generally identified by reference numeral 300, according to the present invention The apparatus 300 comprises first and second emitters/receivers 310a, 310b (ι e two transceivers 310a, 310b), configured to emit/receive interface sιgnal(s) 315a, 315b/reflected interface sιgnal(s) 325a, 325b The apparatus 300 further comprises a processor 330 and memory 340, in a similar manner to above
The first and the second emitter/receiver 310a, 310b are disposed either side of the apparatus 300 (ι e so as to provide for emission of an interface signal 315a, 315b in opposite directions) It will be appreciated that the emitter/receiver 310 may not be provided on either side, but may be configured to provide directional interface signals 315a, 315b, and thus have the same effect
The processor 330/memory 340 are configured to identify the time taken for the interface signal 315 to be received as a reflected interface signal 325 (time of flight) for each emitter/receiver 310a, 310b
In this embodiment, the apparatus 300 is configured to provide for identification of the relative distance between the apparatus 300 and particular formation ιnterface(s) based on difference in time from emitting and receiving respective interface signals 315a, 315b/reflected interface signals 325a, 325b from the respective first and second emitter/receiver 310a, 310b Figures 7a and 7b show exemplary emissions of interface signals 315a, 315b from the first and second emitter/receiver 310a, 310b respectively, as well as the respective reflected interface signals 325a, 325b received. The time, tD1, is indicative of the relative distance between the apparatus 300 and a first interface. The time, tD2, is indicative of the relative distance between the apparatus 300 and a second interface. The time, t3, is indicative of the relative difference between the distances.
Figures 8a and 8b show an exemplary use of the apparatus 300, provided in combination with a steerable drilling assembly 390. The drilling assembly 290 is configured to drill a bore 350 which extends through a hydrocarbon-bearing formation which includes an intermediate layer of liquid hydrocarbons 370, a lower layer of water 380a and an upper layer of gaseous hydrocarbons 380b.
An interface 375a exists between the liquid hydrocarbon layer 370 and the water layer 380a, and an interface 275b exists between the liquid hydrocarbon layer 370 and the gas layer 380b. Each interface 375a, 375a is approximated by a curvilinear representation. Again, it will be appreciated that each interface 375a, 375b may extend to a depth, and/or may be defined by a boundary region provided by water/oil/gas occupying the same porous formation.
In use, the drilling assembly 390 advances a bore 350. However, the apparatus 300 is configured to determine the difference, t3, in the time of flight between the first and second interface signal 315a, 315b/reflected interface signal
325a, 325b so as to provide for monitoring/identifying the relative distance between the apparatus 300 and hydrocarbon/water/gas interface 375a, 375b.
The apparatus 300 is configured to provide a monitoring signal to the drilling assembly 390, to allow the drilling assembly 390 to adapt the direction (e.g. inclination, etc.) of the bore 350 depending on the time t3 so as to maintain the drilling assembly 390 (and thus the bore) roughly equidistant between the first and second interfaces 375a, 375b (as shown by D1 , D2, in Figure 8b) and suitably within the layer of liquid hydrocarbons 370. That is to say that the apparatus 300/drilling assembly 390 are configured to try to reduce t3 to zero/roughly zero.
The rate of change of time, dt3/dt, provides for the rate of change of interface
375a, 375b with respect to the advancement of the drilling assembly 390. In a similar manner to - above, the actual distance may be determined by providing/estimating/approximating the speed of sound in the hydrocarbon bearing formation 370.
Although in this embodiment, the drilling assembly 390 is configured to self- correct using the monitoring signal/difference in time of flight, t3, in other embodiments, the monitoring signal/difference in time of flight, t3, may be provided to a surface operator or equipment to allow for correction of the drilling assembly 390.
It will also be appreciated that in some embodiments, the apparatus 300 of Figure 6 may be provided by two apparatus 100, 200 of Figure 1 and/or 4. In some embodiments, more than two apparatus 100, 200, 300 may be provided in order to provide for identifying the relative distance to interface(s).
Figure 9 shows a further embodiment of a downhole apparatus, generally indicated by reference numeral 400, according to the present invention. The apparatus 400 comprises a plurality of emitters/receivers 410 (i.e. transceivers 410) configured to emit/receive interface signal(s) 415/reflected interface signal(s) 425 in a plurality of directions (not all shown for clarity). The apparatus 400 further comprises a processor 430 and memory 440, in a similar manner to above, in communication with the emitters/receivers 410. The emitter/receivers 410 are disposed peripherally around the apparatus 400 (i.e. so as to provide for emission of an interface signal in a plurality of differing directions). The emitter/receivers 410 are disposed peripherally around the apparatus 400 such that a particular emitter/receiver 410 has a corresponding emitter/receiver 410 disposed in an opposite sense.
The apparatus 400 is configured such that each emitter/receiver 410 emits an identifiable interface signal 415 (i.e. by modulating the interface signal 310 to have a unique identifier, such as by amplitude modulation, phase-shift keying, etc of the emitted interface signal 415) The apparatus 400/processor 430 is configured to identify a particular reflected interface signal 425 based on the unique identifier modulated in the reflected interface signal 425 That is to say that irrespective of the number of emitter/receivers 410, the apparatus 400 is able to determine the time of flight of particular interface signals 415/reflected interfaces signals 425 at a particular emitter/receiver 410 (ι e to prevent/avoid/reduce the chance of interference of signals)
Figure 10a shows the apparatus 400 provided with a drilling assembly 490 for drilling a bore 450 which extends through a hydrocarbon-bearing formation which includes an intermediate layer of liquid hydrocarbons 470, a lower layer of water 480a and an upper layer of gaseous hydrocarbons 480b, in a similar manner to that described above, in which respective interfaces 475a, 475b exist
Again, each interface 475a 475a may extend to a depth, and/or may be defined by a boundary region provided by water/oil/gas occupying the same porous formation Figure 10b shows a cross-section at P-P in Figure 10a As is shown, the interfaces 475a, 475b as not simply curvilinear in a two dimensional manner, but provide a curved/irregular planer interface
In use, the drilling assembly 490 advances a bore 450 The apparatus 400 is configured to determine the difference in the time of flight between opposing emitters/receivers 410 so as to provide for monitoring/identifying the relative distance between the apparatus 300 and hydrocarbon/water/gas interface 375a, 375b
For example (as shown in Figure 10b), the apparatus is configured to determine the difference in time of flight between each pair of respective emitters/receivers 410 (e g measure signals K1 and K2 so as to provide for identification of the relative distance of emιtter/receιver-K1/K2 and respective interfaces 475a, 475b and signals L1 and L2 so as to provide for identification of the relative distance of emιtter/receιver-L1/L2 and respective interfaces 475a, 475b) The apparatus 400 is configured to provide a monitoring signal to the drilling assembly 490, to allow the drilling assembly 490 to adapt the direction (e g inclination, etc ) of the bore 450 depending on each of the respective time of flight evaluations and therefore maintaining the drilling assembly 490 (and thus the bore) roughly equidistant between the first and second planer interfaces 475a, 475b
Again, although in this embodiment, the drilling assembly 490 is configured to self-correct, in other embodiments, the monitoring signal/difference in time of flight may be provided to a surface operator or equipment to allow for correction of the drilling assembly 490
In some embodiments, the emitters/receivers 410 may not be used as pairs, but may be used individually, or may be used in groups more than two, such as three, four, six, etc In addition, although as described as a plurality of emitters/receivers 410, in some embodiments, the emitters/receiver may be provided by one, or more directional emitters/receivers (e g beamforming) Similarly, while each interface signal has been described as modulated, in other embodiments, each signal may be spaced by time (e g provided in a particular window), such as by using time division multiple access (TDMA)
It will be appreciated that in alternative embodiments, the provision of unique identifiers may not be used The directionality of some or each of the interface signals (e g by using a phased-array antenna) may allow for reduction in the chance of interference between the signals Alternatively, each or some emitters/receiver 410 may be configured to emit at a particular time division (ι e an interface signal being emitted during a particular window)
Figure 11 shows a flowchart 500 of a method of identifying the relative position of formation ιnterface(s) There is provided a step 510 of emitting particular interface sιgnal(s) from an apparatus These interface signals are received, indicted by step 520 as reflected interface sιgnal(s) at the apparatus The reflected interface sιgnal(s) have been reflected from particular formation ιnterface(s) in a downhole environment (e.g. between oil/water interface). A step 530 is then performed for identification of the relative distance between the apparatus and particular formation interface(s) based on characteristics of reflected interface signal(s). The characteristics may be based on the time of flight of a particular interface signal/reflected interface signal (or plurality of interface signals/reflected interface signals). The characteristics may be based on the difference between two (or more) time of flight evaluations of particular interface signal/reflected interface signal (or plurality of interface signals/reflected interface signals).
At step 540, the method comprises providing for correction of the direction of a drill bit or drilling assembly or the like using the characteristics of reflected interface signal(s) based upon the relative distance between the apparatus and particular formation interface(s). At step 550 the method comprises providing for monitoring of a level of a formation interface in a downhole environment based upon the relative distance between the apparatus and particular formation interface(s) by using characteristics of reflected interface signal(s).
It will be appreciated that while in the above embodiment, acoustic emissions are described, it will readily be appreciated that electromagnetic emissions may be used (e.g. extremely low frequency (ELF) electromagnetic emissions). In addition, although particular embodiments have been described using substantially horizontal/vertical orientation with respect to a surface, in other embodiments, bores
150, 250, 350, 450 may extend in any number of directions, and are not limited to those described.
In addition, and in view of the foregoing description, it will be evident to a person skilled in the art that various modifications to either embodiment may be made within the scope of the invention. Similarly, the apparatus 100, 200, 300, 400 and/or methods disclosed may have other functions/steps, in addition to those described. While it has been shown and described particular embodiments of the invention, it will be understood that various omissions, substitutions and/or changes in the form and details of the apparatus, etc., and methods described may be made by those skilled in the art without departing from the spirit of the invention.
For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognised that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. Furthermore, in the claims any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.

Claims

1. A downhole apparatus for identifying the position of an interface within a subterranean formation, said apparatus comprising:
a signal emitter configured to emit a signal; and
a signal receiver configured to receive the signal following reflection from a subterranean interface;
wherein a relative distance between the apparatus and the subterranean interface is determined from a characteristic of the reflected signal.
2. The apparatus according to claim 1 , wherein the apparatus is configured for use in ensuring that a desired location of the apparatus relative to a subterranean interface is achieved and/or maintained.
3. The apparatus according to claim 1 or 2, in which the subterranean interface is defined by a condition change within a subterranean environment, the condition change comprising a change in one or more of: pressure, porosity, temperature, density, bulk modulus, chemistry.
4. The apparatus according to any preceding claim in which a relative distance between the apparatus and a subterranean interface is determined from a time of flight characteristic or measurement of the signal. 5. The apparatus according to any preceding claim wherein the signal comprises a plurality of frequencies. 6 The apparatus according to claim 5, wherein at least one frequency is selected in accordance with a dimension, known or estimated, of the subterranean interface 7 The apparatus according to claim 6, wherein the selected frequency is selected such that the wavelength is greater than a known or estimated thickness of the subterranean interface
8 The apparatus according to any of the claims 5 to 7, in which the signal comprises a plurality or a range of frequencies to identify interfaces of differing thicknesses
9 The apparatus according to any preceding claim, wherein the apparatus is adapted to emit a plurality of signals in a plurality of directions
10 The apparatus according to claim 9, wherein the apparatus is configured to determine a shape of a subterranean interface
11 The apparatus according to claim 9 or 10, wherein the apparatus is adapted to determine a relative distance between the apparatus and a plurality of subterranean interfaces
12 The apparatus according to claim 11 , wherein the apparatus is configured to be appropriately positioned, translated, or maintained at a desired position between a plurality of determined subterranean interfaces
13 The apparatus according to claim 12, wherein the apparatus is configured to permit the relative distance between the apparatus and a determined subterranean interface to be determined in accordance with a difference in the time of flight of a pair of signals.
14. The apparatus according to any preceding claim, wherein the apparatus is configured to emit uniquely identifiable signals.
15. The apparatus according to any preceding claim configured to provide an output in the form of a monitoring signal. 16. The apparatus according to claim 15, wherein the apparatus is configured to provide a monitoring signal when a signal characteristic, such as time of flight, is less or more than a predetermined threshold.
17. The apparatus according to any preceding claim wherein the apparatus is adapted to be mounted on or form part of a drilling assembly for use in drilling a bore.
18. The apparatus according to claim 17, wherein the apparatus is configured to determine a relative distance between the apparatus and a subterranean interface while a bore is being drilled by an associated drilling assembly.
19. The apparatus according to any of the claims 1 to 16, wherein the apparatus is adapted to be located at a fixed downhole location, such that the apparatus is adapted to monitor any changes in the relative distance between the fixed location and a subterranean interface
20. The apparatus according to claim 19, wherein the apparatus is to be located within a production zone within a production well bore.
21. The apparatus according to claim 20, wherein the apparatus is adapted to identify and monitor the location of an interface to permit intervention within a production zone in the event of encroachment of such an interface into said zone. 22. The apparatus according to any preceding claim, wherein the signal comprises an acoustic signal.
23. A method of identifying the position of an interface within a subterranean formation, said method comprising the steps of:
emitting a signal from a downhole apparatus;
receiving the signal at the downhole apparatus following reflection from a subterranean interface; and
determining a relative distance between the apparatus and the subterranean interface from a characteristic of the reflected signal.
24. The method according to claim 23, further comprising controlling a downhole activity or assembly based on the identified relative location of a subterranean interface. 25. The method according to claim 24, comprising controlling a drilling assembly to form a bore which is positioned at a desired distance from a subterranean interface.
26. The method according to claim 23 comprising monitoring the location of a subterranean interface relative to a fixed downhole location, wherein the downhole location comprises a production zone.
27. A directional drilling apparatus, said apparatus comprising: a steerable drilling assembly;
a downhole apparatus according to any of the claims 1 to 16;
wherein the steerable drilling assembly is controlled in accordance with an output from the downhole apparatus.
28. Apparatus for controlling production from a subterranean reservoir, said apparatus comprising:
a production conduit arranged to be in fluid communication with a subterranean reservoir at a production zone;
a downhole apparatus according to any of the claims 1 to 16 and configured for identifying advancement of a subterranean interface towards the production zone; and
an isolation arrangement adapted to be activated to isolate fluid communication between the production conduit and the subterranean formation when the subterranean interface reaches a predetermined distance from the production zone.
29. Apparatus substantially as described with reference to the figures and/or the description.
30. Methods substantially as described with reference to the figures and/or the description.
PCT/GB2010/001392 2009-07-24 2010-07-22 Downhole apparatus and method WO2011010101A2 (en)

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