Patent Application
20100013663
This invention relates, in general, to communication systems for transmitting data between downhole equipment and surface equipment and, in particular, to a downhole telemetry system that transmits optical signals via an optically transmissive fluid media disposed in a wellbore.
Without limiting the scope of the present invention, its background is described with reference to sand control completions, as an example.
It is well known in the subterranean well drilling and completion art that relatively fine particulate materials may be produced during the production of hydrocarbons from a well that traverses an unconsolidated or loosely consolidated formation. Numerous problems may occur as a result of the production of such particulate. For example, the particulate causes abrasive wear to components within the well, such as tubing, flow control devices, safety devices and the like. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids using surface processing equipment.
One method for preventing the production of such particulate material is to gravel pack the well adjacent to the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a work string to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a relatively coarse particulate material, such as sand, gravel or proppants, which are typically sized and graded and which are typically referred to herein as gravel, is then pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through a wash pipe or both. In either case, the gravel is deposited around the sand control screen to form the gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the fine particulate materials carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of these particulate materials from the formation.
In other cases, it may be desirable to stimulate the formation by, for example, performing a formation fracturing and propping operation prior to or simultaneously with the gravel packing operation. This type of treatment process is commonly referred to as a frac pack. During this treatment process, hydraulic fractures are created in the hydrocarbon bearing formation, which increase the permeability of the formation adjacent the wellbore. According to conventional practice, a fracture fluid such as water, oil, oil/water emulsion, gelled water or gelled oil is pumped down the work string with sufficient volume and pressure to open multiple fractures in the production interval. The fracture fluid may carry a suitable propping agent, such as sand, gravel or proppants, which are typically referred to herein as proppants, into the fractures for the purpose of holding the fractures open following the fracturing operation. In addition, these proppants are deposited around the sand control screen to form the gravel pack as described above. As such, frac packs can successfully enhance fluid production from the formation while also preventing the production of particulate materials from the formation.
Typically, downhole parameters such as pressure and temperature are obtained and recorded during such treatment processes with one or more downhole sensors. The information obtained by the sensors is later downloaded into surface or remote computers once the treatment operation is complete and the sensors have been tripped out of the wellbore. It has been found, however, that the quality of the treatment operation is evaluated only after such downhole sensors are brought to the surface. As such, the information obtained by the sensors is not supplied in a manner timely enough to allow modifications to the treatment operation. Accordingly, a need has arisen for a communication system for transmitting data between downhole equipment and surface equipment that is operable to provide real-time information relating to parameters and conditions downhole such that modifications to a treatment operation may occur, if desired.
The present invention disclosed herein provides a communication system for transmitting data between downhole equipment and surface equipment. The system of the present invention is operable to provide real-time information relating to parameters and conditions downhole such that modifications to a treatment operation may occur, if desired.
In one aspect, the present invention is directed to a downhole telemetry system that is disposed within a wellbore. The downhole telemetry system includes a downhole transmitter operable to optically transmit a data stream and a downhole receiver operable to receive the optically transmitted data stream. An optically transmissive fluid is disposed in the wellbore and provides a medium for the optical transmission of the data stream between the downhole transmitter and the downhole receiver.
In one embodiment, a tubular string supports the downhole transmitter and the downhole receiver. In this embodiment, the optically transmissive fluid may be disposed in an annulus between the tubular string and the wellbore, in an interior of the tubular string or both. In some embodiments, the downhole transmitter may be positioned uphole of a downhole receiver, downhole of a downhole receiver or both to enable communication of surface commands downhole, downhole data uphole or both. In certain embodiments, the optical transmission of the data stream may be accomplished using a light beam such as a laser. The optically transmissive fluid may be a brine and may include suspended solids.
In another aspect, the present invention is directed to a method for transmitting data within a wellbore. The method includes disposing an optically transmissive fluid within the wellbore to provide a medium for optical transmission of data and optically transmitting a data stream through the optically transmissive fluid between a downhole transmitter and a downhole receiver.
The method may also include disposing suspending particles in the optically transmissive fluid, transmitting light through the optically transmissive fluid or transmitting laser through the optically transmissive fluid.
In a further aspect, the present invention is directed to a downhole telemetry system disposed within a wellbore. The downhole telemetry system includes a downhole transmitter operable to optically transmit a data stream, a downhole repeater operable to receive the optically transmitted data stream from the downhole transmitter and to optically retransmit the data stream and a downhole receiver operable to receive the optically retransmitted data stream. An optically transmissive fluid is disposed in the wellbore and provides a medium for the optical transmission of the data stream between the downhole transmitter and the downhole repeater and for the optical retransmission of the data stream between the downhole repeater and the downhole receiver.
In one embodiment, a tubular string supports the downhole transmitter, the downhole repeater and the downhole receiver. In this embodiment, the optically transmissive fluid may be disposed in an annulus between the tubular string and the wellbore, an interior of the tubular string or both. In certain embodiments, a plurality of downhole repeaters may be disposed within the wellbore between the original downhole transmitter and the final downhole receiver. In this embodiment, each of the downhole repeaters is operable to receive the optically transmitted data stream and to optically retransmit the data stream such that the data stream may be sent over a long distance.
In yet another aspect, the present invention is directed to a downhole telemetry system disposed within a wellbore. The downhole telemetry system includes a first downhole transmitter operable to transmit a data stream via a first transmission mode, a first downhole receiver operable to receive the data stream transmitted via the first transmission mode, a second downhole transmitter communicably associated with the first downhole receiver and operable to retransmit the data stream via a second transmission mode and a second downhole receiver operable to receive the data stream retransmitted via the second transmission mode. In this system, one of the first and the second transmission modes is optical transmission and an optically transmissive fluid that is disposed in the wellbore provides a medium for the optical transmission of the data stream.
In one embodiment, the other of the first and the second transmission modes is selected from acoustic transmission, electromagnetic transmission, electrical transmission and sonar transmission.
In an additional aspect, the present invention is directed to a method for transmitting data within a wellbore. The method includes transmitting a data stream via a first transmission mode, receiving the data stream transmitted via the first transmission mode, retransmitting the data stream via a second transmission mode and receiving the data stream retransmitted via the second transmission mode, wherein one of the first and the second transmission modes is optical transmission and wherein an optically transmissive fluid disposed in the wellbore provides a medium for the optical transmission of the data stream.
For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.
Referring initially to
A typical completion process using gravel packing apparatus 40 having integrated sensors 42 will now be described. First, the production interval 68 adjacent to formation 14 is isolated. Packer 46 seals the upper end of production interval 68 and packer 38 seals the lower end of production interval 68. Crossover assembly 44 is located adjacent to gravel packing apparatus 40, traversing packer 46 with portions of crossover assembly 44 on either side of packer 46. When the gravel packing operation commences, the objective is to uniformly and completely fill the production interval 68 with gravel. To help achieve this result, a wash pipe is disposed within gravel packing apparatus 40. The wash pipe extends into crossover assembly 44 such that return fluid passing through gravel packing apparatus 40 may travel through the wash pipe and into annulus 66 for return to the surface.
The fluid slurry containing gravel is pumped down work string 30 into crossover assembly 44. The fluid slurry containing gravel exits crossover assembly 44 through a series of crossover ports and is discharged into annular interval 68, such that the gravel drops out of the slurry and builds up from formation 14, filling the perforations and annular interval 68 around gravel packing apparatus 40 forming the gravel pack. Some of the carrier fluid in the slurry may leak off through the perforations into formation 14 while the remainder of the carrier fluid passes through gravel packing apparatus 40, that is sized to prevent gravel from flowing therethrough. The fluid flowing back through gravel packing apparatus 40, as explained above, flows back to the surface. This process progresses along the entire length of gravel packing apparatus 40 such that annular interval 68 becomes completely packed with the gravel. Once annular interval 68 is completely packed with gravel, the gravel pack operation may cease.
Throughout the gravel placement process, sensors 42 that are operably associated with gravel packing apparatus 40 and wired communication link 60 are used to monitor the entire gravel packing operation and provide substantially real time data relating to the gravel placement. Sensors 42 are position in a variety of circumferential, axial and radial locations relative to gravel packing apparatus 40. For example, as seen in
As illustrated in
Referring again to
Optical communication component 48 operates as a transducer to convert the digitally encoded electrical signal into a digitally encoded optical data stream in the form of light radiation such as a laser. In a preferred embodiment, optical communication component 48 emits coherent light radiation in a narrow, low-divergence monochromatic beam with a well-defined wavelength. Optical communication component 48 includes a transmitter that transmits the optical data stream to optical communication component 50 that includes a receiver. The optical data stream is sent in annulus 66 which contains an optically transmissive fluid medium 64. Suitable optically transmissive fluids include clear fluids such as water as well as fluids containing various suspended particles such as brines that may includes salts such as sodium chloride, sodium formate, calcium chloride, calcium bromide, zinc chloride, zinc bromide, potassium chloride, potassium bromide, potassium formate, caesium formate and the like. Optically transmissive fluid medium 64 may alternatively or additionally include other suspended particles including engineered particles of glass or polymers preferably having flat surfaces or other desirable refraction surfaces.
In a highly optically transmissive medium, the digitally encoded optical data stream will tend to travel in the straight path maintaining its narrow beam format. As most wellbores do not provide a straight path, the optically transmissive fluid medium of the present invention uses the suspended particles to scatter the light beam, thus allowing the information carried in the digitally encoded optical data stream to travel between the optical communication components of the present invention. Specifically, scattering allows the digitally encoded optical data stream to deviate from a straight trajectory due to the localized non-uniformities created by the suspended particles in optically transmissive fluid medium 64. As the suspended particles in optically transmissive fluid medium 64 cause a large number of scattering events of the digitally encoded optical data stream, the path of the digitally encoded optical data stream diffuses to fill the entire annulus 66 with light radiation.
In the illustrated embodiment, optical communication component 50 is positioned between optical communication component 48 and optical communication component 52 to provide amplification and repeater functionality. Specifically, optical communication component 50 is positioned relative to optical communication component 48 such that the light radiation intensity is sufficient at optical communication component 50 to read the data digitally encoded within the optical data stream. Preferably, optical communication component 50 optically or electrically processes the data stream and retransmits the data stream as another digitally encoded optical data stream to optical communication component 52.
Even though
In the illustrated embodiment, optical communication component 52 includes a transducer that converts the digitally encoded optical data stream to an electrical signal such that the data stream may be passed through blowout preventers 24. Specifically, as blowout preventers 24 create a discontinuity in the optically transmissive fluid medium 64, another communication mode is used. In this embodiment, a wired communication link disposed within pipe segment 62 provides a communication medium for communication between optical communication component 52 and optical communication component 54 across blowout preventers 24. Specifically, as best seen in
Continuing on the communication path depicted in
As large amounts of information can be transmitted optically in substantially real time using the present invention, the information may be used to make changes in the treatment process that enhance the quality of the treatment process. As one example, it may desirable to open certain sliding sleeves or valves associated with the wash pipe disposed within gravel packing apparatus 40 such that the return path for fluids is altered. In this case, such a command can be sent to the appropriate sensor 42 that can actuate such a sliding sleeve or valve. The command can be sent using the telemetry system described above as a downlink. Specifically, a digitally encoded electrical command may be sent to optical communication component 58 that converts the digitally encoded electrical command into a digitally encoded optical command which is sent via optically transmissive fluid medium 64 to optical communication component 56 which in turn retransmits the digitally encoded optical command for receipt by optical communication component 54. The command is then send from optical communication component 54 to optical communication component 52 via the wired communication link disposed within pipe segment 62. The optical retransmission continues from optical communication component 52 to optical communication component 50 and finally to optical communication component 48 which converts the digitally encoded optical command to a digitally encoded electrical command that is sent to the appropriate sensor 42 via wired communication link 60. Actuator 88 of sensor 42 then causes the actuation of the desired sliding sleeve or valve. In using the telemetry system of the present invention as a downlink, it may be desirable to use a beam of coherent light radiation in a narrow, low-divergence monochromatic beam with a different well-defined wavelength than that used for data communication in the uphole direction. Likewise, multiple beams of coherent light radiation in a narrow, low-divergence monochromatic beam with different well-defined wavelengths can be used simultaneously to provide multiple channels of communication in either the uphole direction, the downhole direction or both.
The telemetry system of the present invention may also be used to enhance a frac pack operation. In certain frac pack completions, it is desirable to perform a mini frac prior to performing the full fracture stimulation and gravel packing treatment. Typically, the mini frac is performed using a relative small volume of frac fluid to test the formation response to the proposed treatment regime. In such a treatment scenario, the frac fluid is pumped down work string 30, through crossover assembly 44 into annular interval 68, through the perforations and into formation 14 without taking return fluids. During this process, sensors 42 are used to monitor various aspects of the mini frac, such as temperature and pressure at various locations and particularly temperature during the bleed-off period. As the mini frac is relatively short in duration, the data obtained during the mini frac is preferably stored by sensors 42 until the mini frac is complete. At this point, it may be desirable to circulate an optically transmissive fluid into the well through which the digitally encoded optical data stream generated by the optical communication components may be transmitted. Following the communication path described above, the data obtained by sensors 42 may be sent to the surface via optical communication components 48, 50, 52, 54, 56, 58 and the wired communication link associated with pipe segment 62. This substantially real time information can then be used to alter or refine the planned frac pack treatment operation.
Even though
As described above with reference to the wired communication link disposed within pipe segment 62, the optical communication components of the present invention can be integrated into a telemetry system the utilizes one or more other data transmission modes. As best seen in
Referring next to
Upon electrical excitation, these transducers generate vibrations, i.e. acoustic waves, the work string 30 which provide a means of telemetering information. Specifically, after sensors 42 collect data, this data is encoded into an electrical waveform which drives the electromechanical transducer of acoustic communication component 104 which generates acoustic waves in work string 30 which travel up work string 30 and are received by acoustic communication component 106 this serves as an intermediate repeater. Acoustic communication component 106 retransmits the data by again generating acoustic waves in work string 30 which travel up work string 30 and are received by acoustic communication component 108. The received acoustic signals are converted back to electrical signals by each of the receiving transducer and decoded to recover the data obtained by sensors 42.
Acoustic communication component 108 feeds a digitally encoded electrical signal to the wired communication link disposed within pipe segment 62 which forwards the data carried in the electrical signal to optical communication component 54 for transmission to the surface via optical communication components 56, 58 and optically transmissive fluid medium 64 as described above. In this manner, an acoustic telemetry system can be used for data transmission downhole with the aid of the optical transmission mode of the present invention to overcome the problems associates with acoustic transmissions in the noisy environment provided in subsea conduit 18.
Referring next to
The electromagnetic transmitter may be a direct connect type transmitter that utilizes an output voltage applied between two electrical terminals that are electrically isolated from one another to generate electromagnetic waves 112 that are radiated into the earth carrying the information obtained by sensors 42. Alternatively, the transmitter may include a magnetically permeable annular core, a plurality of primary electrical conductor windings and a plurality of secondary electrical conductor windings which are wrapped around the annular core. Collectively, the annular core, the primary windings and the secondary windings serve to approximate an electrical transformer which generates electromagnetic waves 112.
Electromagnetic waves 112 travel through the earth and are received by subsea repeater 114 located on sea floor 16. Subsea repeater 114 may detect either the electrical field (E-field) component of electromagnetic waves 112, the magnetic field (H-field) component of electromagnetic waves 112 or both. As electromagnetic waves 112 reach subsea repeater 114, a current is induced in subsea repeater 114 that carries the information originally obtained by sensors 42. The current is fed to an electronics package within subsea repeater 114 for processing.
After the electrical signal has been processed, it is forwarded to an sonar modem 116 that will transform the electrical signal into sound waves 118. The information may be encoded into sound waves 118 by sonar modem 116 using, for example, frequency shift keying (FSK) or multiple frequency shift keying (MFSK). Sound waves 118 are transmitted through the sea carrying the information originally obtained by sensors 42. Sound waves 118 are then picked up by sonar modem 120 and forwarded to the surface via electric wire 122. As with each of the above described telemetry systems, the telemetry system described with reference to
While this invention has been described with a reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.
