CA2885864C

CA2885864C - Communication using a spacer fluid

Info

Publication number: CA2885864C
Application number: CA2885864A
Authority: CA
Inventors: Dale E. Jamison
Original assignee: Halliburton Energy Services Inc
Current assignee: Halliburton Energy Services Inc
Priority date: 2012-10-31
Filing date: 2013-10-28
Publication date: 2018-10-30
Anticipated expiration: 2033-10-28
Also published as: AU2013338258A1; US20140118157A1; EP2888446A4; AR093251A1; EP2888446A1; AU2013338258B2; CA2885864A1; WO2014070648A1

Abstract

Disclosed are systems and methods for transmitting commands from a surface to downhole electronic equipment using pills of a spacer fluid. One method of communicating down a wellbore may include providing a flow of a first fluid along a flow path, introducing a series of one or more pills of a second fluid into the flow of the first fluid at a first point along the flow path, and detecting the series of one or more pills of the second fluid at a second point along the flow path, the second point being separated from the first point. In certain embodiments, a series of brine pills may be introduced into a flow of a drilling fluid.

Description

COMMUNICATION USING A SPACER FLUID
BACKGROUND
[0001] The present invention relates generally to downhole communication systems and methods and, more particularly, to systems and methods for transmitting commands from the surface to downhole electronic equipment using pills of a spacer fluid.

[0002] Modern hydrocarbon drilling and production operations requires the use of electronic equipment in the downhole environment. For example, a drill string or accompanying bottom-hole assembly may include active sensors that obtain information about the downhole environment such as the various characteristics and parameters of the earth formations traversed by the borehole, data relating to the size and configuration of the borehole itself, pressures and temperatures of ambient downhole fluids, and other vital downhole parameters. Furthermore, it may be advantageous to remotely activate a downhole tool, such as a reamer, only after the tool is in position and to be able to select one of a plurality of functions after the tool is activated.

[0003] Providing command signals to the downhole electronic equipment can be problematic for a number of reasons. Electrical signal wires running down the bore hole may become cut by abrasion or twisted and broken by the turning drill string. Also, the ambient downhole environment may interfere with reception of acoustic signals sent from the surface and, in addition, signal attenuation for a deep well may reduce the strength of an acoustic signal below a reception threshold of the equipment even in the absence of interference.

[0004] In certain drilling locations, the equipment required to provide command signals via conventional methods, such as acoustic pulses, may not be available while it is still desirable to send a signal to a piece of downhole electronic equipment. Moreover, in certain drilling locations, the ambient conditions may have an adverse effect on sensitive surface equipment and it may be advantageous to use more robust methods to send commands to downhole equipment.

SUMMARY OF THE INVENTION

[0005] The present invention relates generally to downhole communication systems and methods and, more particularly, to systems and methods for transmitting commands from the surface to downhole electronic equipment using pills of a spacer fluid.

[0006] In certain embodiments, a method of communicating is disclosed that may include the steps of providing a flow of a first fluid along a flow path, introducing a series of one or more pills of a second fluid into the flow of the first fluid at a first point along the flow path, and detecting the series of one or more pills of the second fluid at a second point along the flow path that is separated from the first point.

[0007] In certain embodiments, a communication system is disclosed that may include a fluid valve having a first input fluidly coupled to a source of a first fluid exhibiting a first value of a physical property, a second input fluidly coupled to a source of a second fluid exhibiting a second value of the physical property, and an output fluidly coupling the first and second inputs to a flow path. The communication system may also include a controller communicatively coupled to the fluid valve and configured to actuate the fluid valve so as to provide a flow of the first fluid to the flow path and introduce a series of one or more pills of the second fluid into the flow of the first fluid. The communication system may also include a sensor arranged within the flow path and configured to detect the physical property and differentiate between the first value and the second value, thereby detecting the series of one or more pills of the second fluid.

[0008] In certain embodiments, a method of communicating with a downhole tool is disclosed that may include the step of providing a flow of a drilling fluid from a surface valve through a drill string to the downhole tool, wherein the drilling fluid exhibits a first value of a physical property. The method may also include the step of introducing one or more pills of a spacer fluid into the flow of the drilling fluid via the surface valve, wherein the spacer fluid exhibits a second value of the physical property that is different from the first value. The method may also include the step of detecting the one of more pills of the spacer fluid at the downhole tool.

[0009] The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the preferred embodiments that follows.
BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[0011] FIG. 1 illustrates a land-based oil and gas rig including a downhole communication system that may be employed to provide signals to one or more downhole electronics, equipment, or tools, according to one or more embodiments.

[0012] FIG. 2 is a schematic diagram of an exemplary communication system configured to provide a signal down a drill string, according to one or more embodiments.

[0013] FIG. 3 is a block diagram of an exemplary communicative coupling of the valve controller and the downhole electronics, according to one or more embodiments.

[0014] FIGS. 4A-4E depict example messages comprising pills of a second fluid injected into a flow of a first fluid, according to one or more embodiments.

[0015] FIGS. 5A-5C depict movement of an example message from the valve to the downhole sensor, according to one or more embodiments.

[0016] FIGS. 6A and 6B illustrate the ideal configuration of a series of pills of a second fluid injected into a flow of a first fluid through a pipe, according to one or more embodiments.

[0017] FIGS. 7A and 7B illustrate a downstream configuration of the same series of pills of a second fluid injected into a flow of a first fluid through a pipe, according to one or more embodiments.
DETAILED DESCRIPTION

[0018] The present invention relates generally to downhole communication systems and methods and, more particularly, to systems and =

methods for transmitting commands from the surface to downhole electronic equipment using pills of a spacer fluid.

[0019] The disclosed embodiments facilitate digital communication with one or more downhole tools and/or mechanisms when conventional communication systems, such as electrical wires or fiber-optic cable, prove untenable. Such digital communication may be used to trigger activation or changes in operating methods or parameters of the one or more downhole tools and/or mechanisms. One or more of the disclosed embodiments allow signals to be sent along a flow path through which a first fluid is flowing using one or more pills of a second fluid injected into the flow of the first fluid. This allows information and commands to be sent downstream along the flow path in the absence of a separate communication system running parallel to the flow path.

[0020] One or more of the disclosed embodiments allow command signals to be sent from a drill rig on the surface to a downhole electronics system via one or more pills of a spacer fluid injected into the existing flow of drilling fluid, i.e., mud, that is already flowing down the-entire length of the drill string. This method is particularly advantageous at drill sites where conventional communication equipment, such as an acoustic pulser, are not available or where the ambient conditions have a detrimental effect on the operation of such equipment.

[0021] As used herein, the term "pill" or variations thereof refers to a coherent quantity of a second fluid that is introduced into a flow of a first fluid through a flow path, such as a pipe, a tube, or an annulus defined between a pipe and a wellbore, for example. The term "pill" may be considered equivalent to the term "spacer" and/or the phrase "fluid spacer." One example of a pill is an air bubble that is injected into a flow of water through a tube. In this example, the water would be considered the first fluid and the air would be considered the second fluid; the air bubble forming a pill of the second fluid within the flow of the first fluid. In some embodiments, a pill may fill the entire cross-section of the flow path through which it is conveyed or otherwise flowing.

[0022] A pill may be characterized as a homogenous geographical region of material that defines one or more borders, divisions, or end surfaces between adjacent fluids or substances. While the borders, divisions, or end surfaces of the pill may not necessarily exhibit planar surfaces oriented perpendicular to the flow of the first fluid, a pill may nonetheless be considered to have a definable length between a leading end surface and a trailing end surface. As will be appreciated, the length of the pill may change as the pill travels along the flow path due to intermixing and/or distortion of the first and second fluids at the opposing surface and trailing end surfaces due to, for example, viscous friction caused by the surrounding rigid structure of the flow path. Pills may be formulated to have specific density and/or rheological properties to help maintain pill integrity and minimized mixing as the pill travels along the flow path. This is a well-known technique for spacer/pill design.

[0023] As used herein, the phrase "spacer fluid" or variations thereof refer to any second fluid that is injected into a flow of a first fluid, thereby providing a definable gap in the first fluid. The spacer fluid may also be used to physically separate one special-purpose fluid from another in a flow of fluid, or otherwise provide a function that is not provided by the first fluid. An example special-purpose fluid related to the oil and gas industry is a drilling fluid or mud that may be conveyed into a wellbore to power and cool a drill bit and subsequently carry material removed by the drill bit back to the surface.
Certain special-purpose fluids may be prone to contamination, so that a pill of a spacer fluid may be introduced into a flow of a first fluid immediately prior to the special-purpose fluid so as to separate the special-purpose fluid from the first fluid. Exemplary spacer fluids include, but are not limited to water, brines, viscosified brines, viscosified water, weighted and viscosified oil-based or water-based drilling fluids, weighted and viscosified brines, oils, combinations thereof, and the like. In some embodiments, chemicals may be added to enhance the performance of the spacer fluid for a particular operation. In at least one embodiment, a pill may be formed of a spacer fluid having certain physical properties such as, but not limited to, surface tension, density, opacity, capacitance, conductivity, magnetism, a particular solids content, salinity, a particular oil/water ratio, a particular refractive index, a chemical concentration, a spectral fingerprint, combinations thereof, or the like.

[0024] As used herein, the phrase "magnetic field strength" or variations thereof refer to any measure of the strength of a magnetic field, including either of the "H" field and the "B" field, as measured by any technique, such as the Hall effect. This phrase includes "B" field characteristics "magnetic flux density" as measured in teslas and "magnetic flux" as measured in webers as well as measurements of the "H" field in amperes per meter and, in the broadest sense, includes any magnetic physical attribute that can be measured such that two samples having different values of a magnetic physical attribute can be differentiated.

[0025] As used herein, the term "pulse" or variations thereof refer to a portion of a signal that is in a first state when the signal may have only either a first state or a second state, i.e., a "digital" signal. The two states may be defined as "high" and "low" or "1" and "0" or other arbitrary designations of two states. As commonly viewed on an oscilloscope, a pulse will have a transition from the low state to the high state that is the start of the pulse, a duration or length wherein the value of the signal is generally high, and a transition from the high state to the low state that is the end of the pulse. Within this disclosure, a pill of a second fluid injected into a flow of a first fluid may be considered to be a pulse of the second fluid, as the first fluid may be considered to be a first state of the flow as the flow passes a fixed point and the second fluid may be considered to be a second state of the flow.

[0026] As used herein, the term "coherence" or variations thereof refer to the physical integrity of a pill made up of a second liquid within a flow of a first fluid as the pill travels through a flow path. Even if a pill starts in a flow path with an ideal configuration, e.g., a cylinder of the second fluid having planar end surfaces, the end surfaces will deform and diffuse as the pill travels along the tube. Coherence is a qualitative measure of how well the fluid of the pill stays together, wherein a pill is generally considered to still be coherent if the unmixed portion of the second fluid is a large fraction of the original length of the pill. Another way of viewing coherence is whether the position of a pill can be determined with an accuracy that is a small fraction of the distance traveled, for example if the position of a pill can be determined to an accuracy of a few hundred feet after having traveled down a 20,000 foot well.

[0027] As used herein, the phrase "electromagnetic radiation" refers to radio waves, microwave radiation, infrared and near-infrared radiation, visible light, ultraviolet light, X-ray radiation and gamma ray radiation.

[0028] As used herein, the term "optical computing device" refers to an optical device that is configured to receive an input of electromagnetic radiation from a substance or sample of the substance, and produce an output of electromagnetic radiation from a processing element arranged within the optical computing device. The processing element may be, for example, an integrated computational element (ICE), also known as a multivariate optical element, used in the optical computing device. The electromagnetic radiation that optically interacts with the processing element is changed so as to be readable by a detector, such that an output of the detector can be correlated to at least one characteristic of the substance being measured or monitored. The output of electromagnetic radiation from the processing element can be reflected electromagnetic radiation, transmitted electromagnetic radiation, and/or dispersed electromagnetic radiation.

[0029] Whether reflected or transmitted electromagnetic radiation is analyzed by the detector may be dictated by the structural parameters of the optical computing device as well as other considerations known to those skilled in the art. In addition, emission and/or scattering of the substance, for example via fluorescence, luminescence, Raman scattering, and/or Raleigh scattering, can also be monitored by the optical computing devices. In some embodiments, suitable structural components for the exemplary optical computing devices are described in commonly owned U.S.
Pat. Nos. 6,198,531; 6,529,276; 7,123,844; 7,834,999; 7,911,605; 7,920,258;
8,049,881; and 8,208,147, and U.S. Pat. App. Serial Nos. 12/094,465 and 13/456,467.
As will be appreciated, variations of the structural components of the optical computing devices described in the above-referenced patents and patent applications may be suitable, without departing from the scope of the disclosure, and therefore, should not be considered limiting to the various embodiments disclosed herein.

[0030] As used herein, the phrase "optically interact" or variations thereof refers to the reflection, transmission, scattering, diffraction, or absorption of electromagnetic radiation either on, through, or from one or more processing elements (i.e., integrated computational elements). Accordingly, optically interacted light refers to electromagnetic radiation that has been reflected, transmitted, scattered, diffracted, or absorbed by, emitted, or re-radiated, for example, using the integrated computational elements, but may also apply to interaction with a fluid or a substance in the fluid.

[0031] As used herein, the term "tool" or variations thereof refer to any downhole mechanism, sensor, or equipment. A tool may perform, but is not limited to, an active operation on a portion of a borehole, provide a service to other downhole equipment, such as a power generator, or measure and report on physical properties and attributes of the borehole or surrounding subterranean formation.

[0032] FIG. 1 illustrates a land-based oil and gas rig 100 including a downhole tool 140, according to one or more embodiments. It should be noted that, even though FIG. 1 depicts a land-based oil and gas rig 100, it will be appreciated by those skilled in the art that the components of the rig 100, and various embodiments of the components disclosed herein, are equally well suited for use in other types of rigs, such as offshore platforms, or rigs used in any other geographical location.

[0033] As illustrated in FIG. 1, a drilling platform 102 supports a derrick 104 having a traveling block 106 for raising and lowering a drill string 108.
A
kelly 110 supports the drill string 108 as it is lowered through a rotary table 112.
The kelly 110 may be, for example, a four or six-sided pipe configured to transfer rotary motion to a turntable 130 and the drill string 108. A drill bit 114 is driven either by a downhole motor and/or via rotation of the drill string from the drilling platform 102 and may include one or more drill collars 127 and 128 arranged at or near the drill bit 114. As the bit 114 rotates, it creates a borehole 116 that passes through various subterranean formations 118. A
pump 120 circulates a drilling fluid (i.e., mud) 126 through a feed pipe 122 to the kelly 110, which conveys the drilling fluid 126 downhole through an interior conduit in the drill string 108 and through one or more orifices in the drill bit 114. The drilling fluid 126 is then circulated back to the surface via the annulus defined between the drill string 108 and the borehole 116 where it is eventually deposited in a retention pit 124. The drilling fluid 126 transports cuttings and debris derived from the borehole 116 into the retention pit 124 and aids in maintaining the integrity of the borehole 116.

[0034] The downhole tool 140 may be coupled to or otherwise form an integral part of the drill string 108.
The downhole tool 140 may be representative of any downhole tool or mechanism known to those skilled in the art and may include, but is not limited to, a bit, a reamer, a reservoir sampling tool, a downhole power generator, a tool to aid in cement placement/position, a wellbore perforation tool, a fluid bypass tool, a Measurement-While-Drilling (MWD) sensor, a Logging-While-Drilling (LWD) sensor, a Magnetic Resonance Imaging (MRI) tool, a Nuclear Magnetic Resonance (NMR) tool, an electromagnetic (EM) telemetry tool, positive or negative mud pulsers, a Pressure-While-Drilling (PWD) sensor, a resistivity sensor, combinations thereof, and the like. These tools and services enable various downhole operations to be performed, including the capture and/or recording of various critical measurements along with transmitting such data to the surface, while drilling the borehole 116. These operations and measurements make it possible to evaluate the subterranean formation 118, maximize drilling performance, and help ensure precise wellbore placement, thereby helping to reduce time and costs. A tool 140 may have one or more functions that can be activated or initiated while the tool 140 is disposed downhole. For example, a reamer may be lowered to a particular depth in a retracted configuration, thereby making the reamer easier to handle as the reamer is being lowered into position, and then the reamer can be activated by a command as disclosed herein to extend the reaming blades and commence reaming. Other tool 140, for example a MRI
tool, may be lowered in an inactive condition and then activated by a command as disclosed herein to begin making measurements and transmitting information to the surface.

[0035] Referring now to FIG. 2, with continued reference to FIG. 1, illustrated is a schematic diagram of an exemplary communication system 200 configured to convey a signal to the downhole tool 140, according to one or more embodiments. The communication system 200 may include a valve 230 that controls the flow of fluids from at least two sources. Specifically, the valve 230 may be configured to control the flow of a first fluid 126 being drawn from the retention pit 124 using one or more pumps 120. In some embodiments, the first fluid is drilling fluid (i.e., mud) and may be provided to the valve 230 at a first inlet 231 defined on the valve. The valve 230 may also be configured to control the flow of a second fluid 250 being drawn from a containment vessel or tank 205 using one or more pumps 220. The second fluid 250 may be provided to the valve 230 at a second inlet 232. In one or more embodiments, the valve 230 may be configured to fluidly couple either the first inlet 231 or the second inlet 232 to an outlet 233 defined on the valve 230 and providing fluid communication to the drill string 108. Accordingly, the valve 230 may be configured to selectively connect either a flow of the first fluid 126 or a flow of the second fluid 250 to the drill string 108.

[0036] The communication system 200 may also include a controller 235 that, in one or more embodiments, includes a programmable processor and memory having a computer-readable medium (not shown). The controller 235 may be communicatively coupled to the valve 230 and configured to operate the valve 230 so as to fluidly connect either the first inlet 231 or the second inlet 232 to the outlet 233, thereby providing either a flow of the first fluid 126 or a flow of the second fluid 250, respectively, to the drill string 108. By properly switching back and forth between a flow of the first fluid 126 or a flow of the second fluid 250, as discussed in greater detail below, the controller 235 can cause the valve 230 to introduce a series of one or more pills of the second fluid 250 into the flow of the first fluid 126.

[0037] Creating a pill of the second fluid 250 in a flow of the first fluid 126 within the drill string 108 can be accomplished by, for example, starting from a configuration where the valve 230 is accepting only the first fluid 126, switching the valve 230 to accepting only the second fluid 250 for a certain, predetermined amount of time, then switching the valve 230 back to accepting only the first fluid 126. The resulting length of the pill of the second fluid within the drill string 108 may be dependent upon several factors including, but not limited to, one or more of the pressures of the first and second fluids 126,250 at their respective inlets 231,232, the size of the respective inlet pipes 121,221 for each inlet 231,232, the cross-sectional flow area of the drill string 108, the length of the drill string 108, the viscosity of the first and second fluids 126,250, the type of pumps 120,220 used, combinations thereof, and the like. Taking into account these several factors, a desired length of a pill within the drill string 108 can be calculated and correspond to a specific time duration for the valve 230 to accept only the second fluid 250 via the second inlet 232. In one or more embodiments, this information can be stored in the controller 235 or calculated as needed by the controller 235.

[0038] As shown in FIG. 2, a series of pills 252 of the second fluid 250 has been introduced into the drill string 108. In particular, the series 252 depicted in FIG. 2 includes two pills of the second fluid 252 with a pill of the first fluid 126 being disposed between the two pills of the second fluid 250. In exemplary operation, the series 252 of pills of the second fluid 250 may be configured to convey information to the downhole tool 140, as discussed in greater detail below with respect to FIGS. 5A-5C.

[0039] The communication system 200 may also include a sensor 240 located, in this example, within the drill string 108 near the drill bit 114.
As will be appreciated, however, the sensor 240 may be located in other locations in the downhole environment, such as at any point along the drill string 108. The sensor 240 may be configured to measure at least one physical property exhibited by both the first and second fluids 126,250. In some embodiments, the second fluid 250 may exhibit a value of the physical property that is different from that exhibited by the first fluid 126, and the sensor 240 may be configured to differentiate between the first fluid 126 and the second fluid 250 based on measuring the corresponding values of the common physical property exhibited by each fluid 126,250. As will be appreciated by those skilled in the art, any physical property that may be different between the first and second fluids 126,250, and that is detectable by the downhole sensor 240, may be used, without departing from the scope of the disclosure. Example physical properties include, but are not limited to, temperature of the fluid, viscosity, electrical conductivity, capacitance, thermal conductivity, magnetic field strength, density, optical transmissibility, spectral fingerprint, an emitted amount of electromagnetic radiation, combinations thereof, or the like.

[0040] By measuring the transition time or duration between the different values of a physical property corresponding to the first and second fluids 126, 250, the sensor 240 may be able to determine a length of each pill of the second fluid 250 as it passes or otherwise interacts with the sensor 240.
In one or more embodiments, the respective durations can be compared to each other without requiring a conversion of the transition time to a measurable length and the relative durations can then be used in place of lengths of the pills in a defined series of pills.

[0041] In at least one exemplary embodiment, the physical property to be detected by the sensor 240 may be electrical conductivity of the first and second fluids 126, 250. Electrical conductivity measurements are often made during hydrocarbon extraction processes in order to characterize rock formations during drilling or otherwise to detect particular downhole fluids or substances.
For instance, conductivity measurements are often performed on the drilling fluid (i.e., mud) that is conveyed into and returned from the borehole 116. In this exemplary embodiment, the first fluid 126 may be drilling fluid that may exhibit a first electrical conductivity, and the second fluid 250 may be a fluid chosen or designed to have a different electrical conductivity than this first fluid 126. For instance, the second fluid 250 may be brine or a brine solution exhibits a higher conductivity than the drilling fluid (i.e., the first fluid 126). The detector may be configured to detect the increased conductivity of the second fluid 250, and thereby conclude that a pill of the second fluid is present.

[0042] In some embodiments, the physical properties of each fluid 126, 250 may be entirely different, and the sensor 240 may be configured to detect the physical property of only the second fluid 250, thereby determining when the one or more pills of the second fluid 250 are present.

[0043] It will be apparent to those of skill in the art that the use of the disclosed communication methods and system are not limited to subterranean drilling operations and communication with downhole equipment. For example, similar methods and systems may be adapted to any system wherein a first fluid is being transported through a flow path, such as a tube or pipeline, and a second fluid may be introduced into the flow in the form of pills in order to digitally communicate with one or more downstream tools and/or mechanisms.
In some embodiments, for instance, an above-ground oil transfer pipeline may use this method to transfer information or commands from a first point along the pipeline to a second point that is downstream from the first point. The pills of the second fluid injected into the flow of the first fluid may include detectable material, such as a fine magnetic powder, or another substance that a suitable sensor may be configured to detect and recognize that a pill of the second fluid is present.

[0044] Referring to FIG. 3, with continued reference to FIG. 2, illustrated is a block diagram of an exemplary communicative coupling of the valve controller 235 and the downhole tool 140, according to one or more embodiments. Intermediate elements of the communication path, for example the valve 230, have been omitted in FIG. 3 to clarify the illustration.
Digital messages are sent by the controller 235 in the form of a defined series of pills 252 of a second fluid 250 disposed within a flow of a first fluid 126 that is traveling along a flow path (e.g., the drill string 108) to the recipient downhole tool 140. The definition of each message includes the number of pills and the relative length of each pill in the series, wherein each pill may have the same or a different length. The controller 235 may include a first library of messages, each message comprising a different series of one or more pills. The controller a 235 may be configured to accept a selection of one of the messages from the library and transmit the message by actuating the valve 230 (FIG. 3), as generally described above, thereby injecting the proper series of pills 252 that correspond to the selected message into the flow of the first fluid 126.

[0045] As discussed above, the downhole tool 140 may include a sensor 240 (FIG. 2) and an accompanying processor and memory (not visible in FIG.
3). The memory may be configured to store a second library of data corresponding to the first library of the controller 235. Upon detecting the pills 252 of the second fluid 250, the sensor 240 may be configured to convey information (e.g., length, number, etc.) relating to the sensed pills 252 to the processor which compares the conveyed information with the data stored in the second library, thereby determining which message is being received. The message may, in one or more embodiments, include a command signal intended to be received by the downhole tool 140. The downhole tool 140 may be configured to execute the command upon receipt, thereby allowing operators on the surface to initiate specific actions by the downhole tool 140.

[0046] In one or more embodiments, there may be a second communication path 270 that places the downhole tool 140 in communication with the controller 235 or other surface electronic module (not shown in FIG.
3).
The second communication path 270 may be a wired or wireless communication link allowing the downhole tool 140 to inform the controller 235 of the receipt of the message or a particular downhole command.

[0047] FIGS. 4A-4E depict example messages comprising series 252 of pills of the second fluid 250 as injected into a flow of the first fluid 126, according to one or more embodiments. In each of FIG. 4A-4E, the first fluid 126 is conveyed through a flow path, such as the drill string 108, from left to right. In these examples, each series 252 includes an "attention" portion 254 followed by a "content" portion 256, with a separation distance 258 between the trailing edge of the last pill of the attention portion 254 and the leading edge of the first pill of the content portion 256. In one or more embodiments, the separation distance 258 comprises at least one of a minimum length and a maximum length. In one or more embodiments, every message is defined to include a common attention portion 254. In other embodiments, however, the attention portion 254 may be omitted from the messaging sequence.

48 PCT/US2013/067040 [0048] In FIG. 4A, the series 252 includes a content portion 256A that is defined to be the command "TURN ON," and would be recognized by the downhole tool 140 as a trigger to initiate or commence its corresponding function. It can seen that this example content portion 256A is configured as a first long pill of the second fluid 250 followed by two short pills. Between each pill of the second fluid 250 is a spacer pill of the first fluid 126 that serves as a spacer between adjacent pills of the second fluid 250. In one or more embodiments, the length of the spacer pills of the first fluid 126 may have at least one of a minimum length and a maximum length. In embodiments where all messages are defined to have content portions with three pills of the second fluid 250, the content portion 256A and the series 252 are both complete at the trailing edge of the third pill of the content portion 256A.

[0049] FIG. 4B illustrates a similar message with an attention portion 254 and a content portion 256B with a different series of pills than the content portion 256A of FIG. 4A. This example content portion 256B is configured to start with two short pills of the second fluid 250 followed by a long pill and this series is defined, for this example, to be a command "SET TO 25%" for a tool 140 such as a valve, wherein 25% may represent an amount that the valve is open, or a rotary tool, wherein 25% may represent the speed of rotation as a percentage of full speed of the rotary tool.

[0050] FIGS. 4C-4E illustrate additional message portions 256C, 256D, and 256E that provide additional example commands of "SET TO 50%," "SET TO
75%," and "SET TO 100%," respectively, wherein the percentages may represent different settings for the example tools 140 of a valve and a rotary tool discussed above. While the example commands shown in FIGS. 4A-4E are each defined with a three-pill content portion 256, where the pills within each content portion are either a "short" length or a "long" length, it will be apparent to those of skill in the art that the number of pills and their respective lengths may vary, without departing from the scope of the disclosure. Accordingly, numerous digital commands may be sent by varying the numbers and lengths of the respective pills, thereby communicating with the downhole tool 104 to undertake equally numerous tasks.

[0051] Referring now to FIGS. 5A-5C, with continued reference to FIG.
2, depicted is an example message as it is conveyed from the valve 230 to the downhole sensor 140, according to one or more embodiments. The first and second fluids 126, 250 may have different measured values of at least one physical property. As described above, the valve 230 facilitates fluid flow of each of the first and second fluids 126, 250 down through the drill string 108 and past a downhole tool 140 arranged therein. The sensor 240, positioned at a second point along the drill string 108, may be configured to detect the difference in the at least one physical property between the first and second fluids 126, 250, thereby determining which fluid is passing the second point at any given instant in time. In this example, the valve 230 allows flow exclusively from either the first or the second fluids 126, 250 and does not include a configuration that shuts off the flow from both fluids 126, 250 at the same time.
The diameter of the drill string 108 and the relative lengths of the pills are not shown to scale in FIGS. 5A-5C and intended only to illustrate the concepts. In one or more embodiments, the lengths of the pills of series 252 may be larger than the diameter of the drill string 108. In one or more embodiments, for example, the lengths of the pills in series 252 may be several times the diameter of the drill string 108 or longer.

[0052] FIG. 5A illustrates the state of the fluids 126, 250 within the drill string 108 at a first time Ti just after the valve 230 has completed injecting the last pill of the second fluid 250 for a series 252 of pills that corresponds to a particular message (e.g., the message illustrated in FIG. 4A). The series 252 includes an attention portion 254 with three short pills of the second fluid followed by a content portion 256 that includes a first long pill followed by two short pills.

[0053] FIG. 5B illustrates the configuration of this same drill string 108 at a second time T2, at which time the trailing edge of the last pill 255C of the attention portion 254 is passing the sensor 240 located at the second point along the flow path of the drill string 108 and the sensor 240 has passed information to the downhole tool 140 that three short pills have been detected. At this point, the tool 240 is aware that a command is about to arrive and may, in certain embodiments, run certain sets of instructions or otherwise reconfigure itself in preparation for receiving the command.

[0054] FIG. 5C illustrates the configuration of this same drill string 108 at a third time 13, at which time the trailing edge of the last pill 257C of the content portion 256 of the series 252 is passing the sensor 240 located at the second point along the flow path of the drill string 108 and the sensor 240 has passed information to the downhole tool 140 that one long and two short pills have been detected. The downhole tool 140 compares this series 252 of pills to the message definitions stored internally within the downhole tool 140 and determines which message corresponds to the detected series of pills of the second fluid, thereby receiving the message that was sent using the valve 230.

[0055] FIGS. 6A and 6B illustrate the an exemplary configuration of a series 254 of pills of a second fluid 250 injected into a flow of a first fluid 126 through a pipe 600, according to one or more embodiments. It can be seen in FIG. 6A that the pills of the second fluid 250 have sharply defined end surfaces 260 or boundaries. Plotting the value of a particular physical property, for example electrical conductivity, along the length of the pipe 600, wherein the first fluid 126 has a "LO" value and the second fluid 250 has a "HI" value, produces a waveform or curve 610, as shown in FIG. 6B. It can be seen that the curve 610 sharply transitions between the HI and LO values and may be considered to be a square wave. Each portion of the curve 610 between a LO-to-HI transition and a subsequent HI-to-LO transition, an example of which is indicated by the dashed-line oval labeled 612 in FIG. 6B, may be considered to be a "pulse" of the second fluid 250 in the flow of the first fluid 126. Thus, the pills of the second fluid 250 in the series 252 may be considered to be equivalent to pulses 612 in a conventional signal. Each pulse 612 has an associated length 614 that is clearly defined in the curve 610.

[0056] FIGS. 7A and 7B illustrate a downstream configuration of the same series 252 of pills of a second fluid 250 injected into a flow of a first fluid 126 through a pipe 600, according to one or more embodiments. As the series 252 flows through the pipe 600, turbulence within the fluids 126 and 250, as well as viscous friction with the walls and flow disturbances created by intermediate piping elements such as coupling and valves (not shown in FIG.
7A) may tend to cause mixing of the fluids 126 and 250 at the boundaries 260.
After some period of time, the boundary 260 of FIG. 6A may no longer be distinguishable but, instead, a transition zone 262 may be generated. A
measured value of the particular physical property may gradually and continuously vary across this transition zone 262 and, when the value is plotted as before along the length of the pipe 600, produces the curve 620 shown in FIG. 7B. It can be seen that the value of the curve 620 varies gradually and it may not be a simple matter to define a transition point between a HI state and a LO state and, subsequently, difficult to determine a length of a pulse 614.

[0057] The integrity, or coherence, of the pills of the second fluid 250 and the first fluid 126 decreases as the length of the transition zone 22 increases. In certain embodiments, the series 252 may be considered to be coherent if it is still possible to detect the individual pills of the second fluid 250 and thereby receive the message of the series 252. As the distance traveled by the series 252 in the pipe 600 increases, the length of the transition zone may increase until there is no longer a portion of the original pill of the second fluid 250 that is pure second fluid 250, whereupon the determination of a HI
state by detecting the value of the physical parameter of the pure second fluid 250 is no longer possible. In certain embodiments, however, it is possible to extend the distance over which a series 252 retains coherence by use of alternate criteria for detecting a pill of the second fluid 250.

[0058] In certain embodiments, the boundaries of a pulse 614 may be defined by the directional crossing of a threshold value that is different than the values associated with the pure fluids 126 and 250. In certain embodiments, a HI threshold may be established that, in this example, is less than the HI
value of curve 610 and, similarly, a LO threshold may be established that is greater than the LO value of curve 610. In certain embodiments, a length 615 may be determined as the distance between a LO-to-HI transition of curve 620 across the HI threshold and a subsequent HI-to-LO transition across the same HI
threshold. In certain embodiments, a length 616 may be determined as the distance between a LO-to-HI transition of curve 620 across the LO threshold and a subsequent HI-to-LO transition across the same LO threshold. In certain embodiments, a length 617 may be determined as the distance between a LO-to-HI transition of curve 620 across the HI threshold and a subsequent HI-to-LO
transition across the LO threshold. In certain embodiments, other thresholds may be established and different criteria applied for determining a boundary between a pill of the second fluid 250 and the first fluid 126.

[0059] Embodiments disclosed herein include A, B, and C:

[0060] Embodiment A: A method of communicating, comprising:
providing a flow of a first fluid along a flow path; introducing a series of one or more pills of a second fluid into the flow of the first fluid at a first point along the flow path; and detecting the series of one or more pills of the second fluid at a second point along the flow path, the second point being separated from the first point.

[0061]
Embodiment A may have one or more of the following additional elements in any combination:

[0062] Element Al:
the method wherein the first fluid comprises a drilling fluid.

[0063]
Element A2: the method wherein: the first fluid exhibits a first value of a physical property; and the second fluid exhibits a second value of the physical property that is different from the first value.

[0064] Element A3:
the method wherein the second fluid comprises a brine.

[0065]
Element A4: the method wherein the physical property is one or more of the following: electrical conductivity; density; magnetic field density;
or a spectral fingerprint.

[0066] Element A5:
the method wherein: each pill of the series of one or more pills comprises a respective length; a first pill of the series of one or more pills comprises a first length; and a second pill of the series of one or more pills comprises a second length not equal to the first length.

[0067]
Element A6: the method wherein: each pill of the series of one or more pills comprises a respective length; a first pill of the series of one or more pills comprises a first length; and a second pill of the series of one or more pills comprises a second length not equal to the first length further comprising:
defining a message with the series of one or more pills of the second fluid, wherein the series comprises a predetermined number of pills, each having a predetermined respective length; sending the message by introducing the series of one or more pills of the second fluid into the flow of the first fluid at the first point; detecting the series of one or more pills of the second fluid with a sensor that is arranged within the flow path at the second point; and receiving the message by determining the message associated with the detected series of pills.

[0068]
Element A7: the method wherein the sensor is communicably coupled to a downhole tool, the method further comprising executing a function of the downhole tool that is associated with the received message.

[0069]
Element A8: the method wherein each message comprises an attention portion and a content portion.

[0070] Embodiment B: A
communication system comprising: a fluid valve having a first input fluidly coupled to a source of a first fluid exhibiting a first value of a physical property, a second input fluidly coupled to a source of a second fluid exhibiting a second value of the physical property, and an output fluidly coupling the first and second inputs to a flow path; a controller communicatively coupled to the fluid valve and configured to actuate the fluid valve so as to provide a flow of the first fluid to the flow path and introduce a series of one or more pills of the second fluid into the flow of the first fluid; and a sensor arranged within the flow path and configured to detect the physical property and differentiate between the first value and the second value, thereby detecting the series of one or more pills of the second fluid.

[0071]
Embodiment B may have one or more of the following additional elements in any combination:

[0072]
Element B1: the communication system wherein: the controller comprises a library of messages, where each message comprises a distinct series of one or more pills of the second fluid by exhibiting a predetermined number and corresponding length of each of the one or more pills of the second fluid; the controller being configured to accept a selection of a message from the library and actuate the fluid valve to create the series of one or more pills of the second fluid that correspond to the message selected, thereby conveying the message within the flow path; and the sensor being further configured to provide information on the predetermined number and corresponding length of each of the one or more pills in each distinct series.

[0073]
Element B2: the communication system wherein the first fluid comprises a drilling fluid and the second fluid comprises a spacer fluid.

[0074]
Element B3: the communication system wherein the library of messages is a first library, and the sensor comprises a second library of messages and is configured to determine which message corresponds to the detected series of one or more pills of the second fluid, thereby receiving the selected message.

[0075] Embodiment C: A
method of communicating with a downhole tool, the method comprising: providing a flow of a drilling fluid from a surface valve through a drill string to the downhole tool, the drilling fluid exhibiting a first value of a physical property; introducing one or more pills of a spacer fluid into the flow of the drilling fluid via the surface valve, the spacer fluid exhibiting a second value of the physical property that is different from the first value; and detecting the one of more pills of the spacer fluid at the downhole tool; and, optionally, wherein the physical property comprises a physical property selected from the group consisting of electrical conductivity, density, magnetic field strength, and spectral fingerprint.

[0076] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein.
Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.
While compositions and methods are described in terms of "comprising," "containing,"

or "including" various components or steps, the compositions and methods can also "consist essentially of" or "consist of" the various components and steps.
All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles "a" or "an," as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

Claims

The invention claimed is:

1. A method of communicating, comprising:
providing a flow of a first fluid along a flow path;
introducing multiple pills of a second fluid into the flow of the first fluid at a first point along the flow path to encode a message in the flow, wherein the first fluid exhibits a first value of a physical property and the second fluid exhibits a second value of the physical property that is different from the first value;
axially adjacent pills of the second fluid are separated by a pill of the first fluid;
wherein transition zones are generated at one or more interfaces between pills of the first fluid and pills of the second fluid, the first and second fluids being at least partially mixed within the transition zones; and the message is defined by one or more of: a number, length and spacing of the pills of the second fluid; and detecting the pills of the second fluid at a second point along the flow path, the second point being separated from the first point and located within a wellbore in a subterranean environment;
determining the message at the second point; and executing a function of a downhole tool according to a command included in the message received at the second point.

2. The method of claim 1, wherein the first fluid comprises a drilling fluid.

3. The method of claim 1 or 2, wherein the physical property is electrical conductivity.

4. The method of claim 1, 2 or 3, wherein the second fluid comprises a brine.

5. The method of any one of claims 1 to 4, wherein the physical property is density.

6. The method of any one of claims 1 to 4, wherein the physical property is magnetic field density.

7. The method of any one of claims 1 to 4, wherein the physical property is spectral fingerprint.

8. The method of any one of claims 1 to 7, wherein at least some of the pills of the second fluid have different lengths in the flow path.

9. The method of any one of claims 1 to 8, wherein the message comprises an attention portion and a content portion.

10. The method of any one of claims 1 to 9, wherein introducing the multiple pills of the second fluid into the flow of the first fluid comprises controlling one or more fluid valves to switch between providing a flow of the first fluid from a first fluid source along the flow path and providing a flow of the second fluid from a second fluid source along the flow path.

11. The method of any one of claims 1 to 10, wherein the first and second fluids are miscible.

12. The method of any one of claims 1 to 11, wherein the second fluid comprises a brine.

13. The method of any one of claims 1 to 12, wherein the length of the pills is determined by determining a distance between transition points at which a value of the physical property crosses a predetermined threshold level having a particular value within a range defined by a first value associated with the first fluid and a second value associated with the second fluid.

14. A communication system comprising:
a fluid valve having a first input fluidly coupled to a source of a first fluid exhibiting a first value of a physical property, a second input fluidly coupled to a source of a second fluid exhibiting a second value of the physical property, and an output fluidly coupling the first and second inputs to a flow path;
a first controller communicatively coupled to the fluid valve and configured to actuate the fluid valve so as to provide a flow of the first fluid to the flow path and introduce multiple pills of the second fluid into the flow of the first fluid, thereby encoding a message in the flow, the message being defined by one or more of: a number, length and spacing of the pills of the second fluid, wherein transition zones are generated at one or more interfaces between pills of the first fluid and the pills of the second fluid, the first and second fluids being at least partially mixed within the transition zones; and a sensor arranged within the flow path in a wellbore in a subterranean environment and configured to detect the physical property and differentiate between the first value and the second value, thereby detecting the pills of the second fluid and the message;
a second controller located in the wellbore and communicatively coupled to the sensor and to a downhole tool also located in the wellbore, wherein the second controller is configured to receive the message detected by the sensor, determine the message, and execute a function of the downhole tool according to a command included in the message.

15. The communication system of claim 14, wherein:
the first controller comprises a library of messages, where each message comprises a distinct series of pills of the second fluid by exhibiting a predetermined number and corresponding length of each of the pills of the second fluid;
the first controller being configured to accept a selection of a message from the library and actuate the fluid valve to create the series of pills of the second fluid that correspond to the message selected, thereby conveying the message within the flow path; and the sensor being further configured to provide information on the predetermined number and corresponding length of each of the pills in each distinct series.

16. The communication system of claim 14, wherein the first fluid comprises a drilling fluid and the second fluid comprises a spacer fluid.

17. The communication system of claim 15 or 16, wherein the library of messages is a first library, and the second controller comprises a second library of messages and is configured to determine which message corresponds to the detected pills of the second fluid, thereby receiving the selected message.

18. The communication system of any one of claims 14 to 17, wherein the first and second fluids are miscible.

19. The communication system of any one of claims 14 to 18, further comprising separating axially adjacent pills of the second fluid with a pill of the first fluid.

20. The communication system of any one of claims 14 to 19, wherein the length of the pills is determined by determining a distance between transition points at which a value of the physical property crosses a predetermined threshold level having a particular value within a range defined by a first value associated with the first fluid and a second value associated with the second fluid.

21. The communication system of any one of claims 14 to 20, wherein at least some of the pills of the second fluid have different lengths in the flowpath.

22. The communication system of any one of claims 14 to 21, wherein the second fluid comprises a brine.

23. The communication system of any one of claims 14 to 22, wherein the message comprises an attention portion and a content portion.