As the sophistication and complexity of petroleum well drilling has increased, so has the demand for comparable increases in the amount of data that can be received from, and transmitted to, downhole drilling equipment. The demand for real-time data acquisition from measurement while drilling (MWD) and logging while drilling (LWD) equipment, as well as real-time precision control of directional drilling, have created a corresponding need for high bandwidth downhole systems to transfer such data between the downhole equipment and surface control and data acquisition systems.
There are currently a wide variety of downhole telemetry systems that are suitable for use in drilling operations. These include both wireless and wired systems, as well as combinations of the two. Existing wireless systems include acoustic telemetry systems, mud pulse telemetry systems, and electromagnetic telemetry systems. In acoustic telemetry systems, sound oscillations are transmitted through the mud (hydroacoustic oscillations), through the drill string (acoustic-mechanical oscillations), or through the surrounding rock (seismic oscillations). Such acoustic telemetry systems generally require large amounts of energy and are limited to data rates at or below 120 bits per second (bps). Mud pulse telemetry systems use positive and negative pressure pulses within the drilling fluid to transmit data. These systems require strict controls of the injected fluid purity, are generally limited to data rates of no more than 12 bps, and are not suitable for use with foam or aerated drilling fluids.
Electromagnetic telemetry systems include the transmission of electromagnetic signals through the drill string, as well as electromagnetic radiation of a signal through the drilling fluid. Transmission of electromagnetic signals through the drill string is generally limited to no more than 120 bps, has an operational range that may be limited by the geological properties of the surrounding strata, and is not suitable for use offshore or in salty deposits. Data transmission using electromagnetic radiation through the drilling fluid (e.g., using radio frequency (RF) signals or optical signals) generally requires the use of some form of a repeater network along the length of the drill string to compensate for the signal attenuation caused by the scattering and reflection of the transmitted signal. Such systems are frequently characterized by a low signal-to-noise ratio (SNR) at the receiver, and generally provide data rates comparable to those of mud pulse telemetry systems.
Existing wired systems include systems that incorporate a data cable located inside the drill string, and systems that integrate a data cable within each drill pipe segment and transmit the data across each pipe joint. Current wired systems have demonstrated data rates of up to 57,000 bps, and at least one manufacturer has announced a future system which it claims will be capable of data rates up to 1,000,000 bps. Wired systems with data cables running inside the drill string, which include both copper and fiber optic cables, generally require additional equipment and a more complex process for adding drill pipe segments to the drill string during drilling operations. Systems that integrate the cable into each drill pipe segment require pipe segments that are more expensive to manufacture, but generally such pipe segments require little or no modifications to the equipment used to connect drill pipe segments to each other during drilling operations.
As already noted, pipe segments with integrated data cables must somehow transmit data across the joint that connects two pipe segments. This may be done using either wired or wireless communications. Drill pipe segments that use wired connections generally require contacting surfaces between electrical conductors that are relatively free of foreign materials, which can be difficult and time consuming on a drilling rig. Also, a number of systems using drill pipes with integrated cables require at least some degree of alignment between pipe segments in order to establish a proper connection between the electrical conductors of each pipe segment. This increases the complexity of the procedures for connecting drill pipes, thus increasing the amount of time required to add each pipe segment during drilling operations.
Drill pipe segments with integrated cables that transmit data across the pipe joint wirelessly include systems that use magnetic field sensors, inductive coupling, and capacitive coupling. Systems that use magnetic field sensors, such as Hall Effect sensors, are generally limited to operating frequencies at or below 100 kHz. Systems that use inductive coupling currently are generally limited to data rates of no more than 57,000 bps. Systems using capacitive coupling require tight seals and tolerances in order to prevent drilling fluid from leaking into the gap between the pipe segments and disrupting communications. Based on the forgoing, existing downhole telemetry systems currently appear to be limited to proven data rates that are below 1,000,000 bps.
A wireless transceiver for transmitting data across a drill pipe joint is described herein. At least some illustrative embodiments include a wireless communication apparatus that includes a housing configured to be positioned inside of, and proximate to an end of, a drill pipe used as part of a drill string. The housing includes an antenna configured such that at least one radio frequency (RF) signal propagation path is substantially parallel to the central axis of the housing, and an RF module coupled to the antenna and configured to couple to a communication cable (the RF module configured to provide at least part of a data re-transmission function between an RF signal present on the antenna and a data signal present on the communication cable). A radiotransparent material, which is transparent to RF signals within the operating frequency range of the RF module, is positioned along the circumference, and at or near an axial end, of the housing that is most proximate to the antenna. At least some axially propagated RF signals, which pass between the antenna and a region axially proximate to said axial end of the housing, pass through the radiotransparent material along the at least one RF signal propagation path.
At least some other illustrative embodiments include a wireless communication system that includes one or more RF transceivers (each transceiver housed within a housing that is configured to be positioned inside, and proximate to an end, of a drill pipe within a drill string, and each transceiver configured to be coupled by a communication cable to a downhole device positioned within the same drill pipe), one or more antennas (each antenna coupled to a corresponding RF transceiver of the one or more RF transceivers, and each antenna housed within the same housing as the corresponding RF transceiver), and one or more radiotransparent spacers that are transparent to RF signals within the operating frequency range of the one or more RF transceivers (each spacer positioned along the circumference, and at or near an axial end, of a corresponding housing that is most proximate to the antenna within the said corresponding housing). A first RF signal is received by first antenna of the one or more antennas through a first radiotransparent spacer of the one or more radiotransparent spacers, which is coupled to a first RF transceiver of the one or more transceivers that extracts receive data from the first RF signal and retransmits the receive data for inclusion in a first data signal transmitted to the downhole device over the data communication cable.
Other illustrative embodiments include a drill pipe used as part of a drill string that includes at least one housing (positioned inside of, and proximate to, one of two ends of the drill pipe), a communication cable that couples a radio frequency (RF) module to a downhole device within the drill pipe (the RF module providing at least part of a retransmission function between a data signal present on the communication cable and an RF signal present on an antenna) and at least one radiotransparent spacers (transparent to RF signals within the operating frequency range of the RF module, and positioned along the circumference of, and at or near an axial end of, the at least one housing, said axial end being an end most proximate to the antenna). The at least one housing includes the antenna (configured such that at least one RF signal propagation path is substantially parallel to the central axis of the drill pipe), and the RF module (coupled to the antenna and to the downhole device). At least some axially propagated RF signals, which pass between the antenna and a region axially proximate to the axial end of the corresponding housings, pass through the radiotransparent spacer along the at least one RF signal propagation path.
Still other illustrative embodiments include a drill string that includes a plurality of drill pipes, each drill pipe mechanically coupled to at least one other drill pipe to form the drill string. Each drill pipe includes at least one housing of a plurality of housings (positioned inside of, and proximate to, one of two ends of the drill pipe), a downhole device positioned inside the drill pipe, a communication cable that couples a radio frequency (RF) transceiver of the at least one housing to the downhole device (the RF transceiver providing at least part of a retransmission function between a data signal present on the communication cable and an RF signal present on an antenna), and at least one radiotransparent spacer (transparent to RF signals within the operating frequency range of the RF transceiver, and positioned along the circumference of, and at or near an axial end of, the at least one housing, said axial end being an end most proximate to the antenna). The at least one housing includes the antenna (configured such that at least one RF signal propagation path is substantially parallel to the central axis of the drill pipe), and the RF transceiver (coupled to the antenna). A first end of a first drill pipe is mechanically coupled to a second end of a second drill pipe, a first housing of the at least one housing of the first drill pipe positioned within the first end, and the at least one housing of the second drill pipe positioned within the second end. At least some axially propagated RF signals that pass between the antennas of the first and second drill pipes also pass through the radiotransparent spacers of both the first and second drill pipes along the at least one RF signal propagation path.
Yet other illustrative embodiments include a method for wireless transmission of data across a joint mechanically connecting two drill pipes within a drill string, which includes receiving (by a radio frequency (RF) transmitter at or near a first end of a first drill pipe) data across a cable from a first device within the first drill pipe; the RF transmitter modulating an RF signal using the data received, and the RF transmitter transmitting the modulated RF signal using a first antenna (through a first radiotransparent material, and across the joint mechanically connecting the first drill pipe to a second drill pipe). The method further includes propagating the RF signal along an RF signal propagation path substantially parallel to the central access of at least one of the two drill pipes, receiving (by an RF receiver using a second antenna at or near a second end of a second drill pipe) the modulated RF signal through a second radiotransparent material (the first and second radiotransparent material both positioned in a space within the joint between the first antenna and the second antenna), the RF receiver extracting the data from the modulated RF signal, and the RF receiver transmitting the data across a cable to a second device within the second drill pipe.
For a detailed description of at least some illustrative embodiments, reference will now be made to the accompanying drawings in which:
Drill string 111 is raised and lowered through rotary table 122, which is driven by Motor 124 to rotate drill string 111 and drill bit 116 (connected at the end of drill string 111 together with bottom hole assembly (BHA) 114). Rotary table 122 provides at least some of the rotary motion necessary for drilling. In other illustrative embodiments, swivel 129 is replaced by a top drive (not shown), which rotates drill string 111 instead of rotary table 122. Additional rotation of drill bit 116 and/or of the cutting heads of the drill bit may also be provided by a downhole motor (not shown) within or close to drill bit 116. Drilling fluid or “mud” is pumped by mud pump 136 through supply pipe 135, stand pipe 134, Kelly pipe 132 and goose necks 130 through swivel 129 and Kelly 128 into drill string 111 at high pressure and volume. The mud exits out through drill bit 116 at the bottom of wellbore 118, travelling back up wellbore 118 in the space between the wellbore wall and drill string 111, and carrying the cuttings produced by drilling away from the bottom of wellbore 118. The mud flows through blowout preventer (BOP) 120 and into mud pit 140, which is adjacent to derrick 102 on the surface. The mud is filtered through shale shakers 142, and reused by mud pump 136 through intake pipe 138.
As already noted, drill string 111 incorporates a communication system constructed in accordance with at least some illustrative embodiments. Such a communication system, an example of which is shown in
Data cables 244 can include either copper wire to transmit electrical signals, or optical fiber to transmit optical signals. Data cables 244 allow information to be exchanged between the devices (e.g., TPUs) within the drill pipes 240. In the example of
Continuing to refer to
Once the data reaches the TPU at the top of drill string 111 (e.g., TPU 246d of
In other illustrative embodiments, downhole device 115 includes drill bit direction control logic for controlling the direction of drill bit 116. Control data flows in the opposite direction from computer system 300, through communications relay transceiver 280 to TPU 246d, across data cable 244d to TPU 242d, and wirelessly to TPU 246c and across cable 244c. The data is eventually transmitted across cable 244b to TPU 242b, wirelessly to TPU 246a, and across data cable 244a to the direction control logic of downhole device 115, thus providing control data for directional control of drill bit 116.
TPU 400 further includes processing logic 464, which in at least some illustrative embodiments includes central processing unit (CPU) 402, volatile storage 404 (e.g., random access memory or RAM), non-volatile storage 406 (e.g., electrically erasable programmable read-only memory or EEPROM), transceiver interface 408 and cable interface (Cable I/F) 410, all of which couple to each other via a common bus 212. CPU 402 executes programs stored in non-volatile storage 406, using volatile storage 404 for storage and retrieval of variables used by the executed programs. These programs implement at least some of the functionality of TPU 400, including decoding and extracting data encoded on a data signal present on data cable 244 (coupled to cable interface 410) and forwarding the data to RF transceiver 462 via transceiver interface 408, as well as forwarding and encoding data received from RF transceiver 462 onto a data signal present on data cable 244. In this manner, processing logic 464, in at least some illustrative embodiments also implements at least part of a data retransmission function between an RF signal present on antenna 466 and a data signal present on data cable 244.
TPU 400 also includes power source 468, which couples to batteries 470. Batteries 470 provide power to both processing logic 464 and RF transceiver 462, while power source 468 converts kinetic energy (e.g., oscillations of the drill string or the flow of drilling fluid) into electrical energy, or thermal energy (e.g., the thermal difference or gradient between different regions inside and outside the drill string) into electrical energy, which is used to charge batteries 470. Other techniques for producing electrical energy, such as by chemical or electrochemical cells, will become apparent to those of ordinary skill in the art, and all such techniques are within the scope of the present disclosure. In other illustrative embodiments (not shown), electrical energy can be provided from the surface and transferred to the TPUs using wireless energy transfer technologies such as WiTricity and wireless resonant energy link (WREL), just to name a few examples.
The radiotransparent material used in both the spacers and housings results in little or no attenuation of radio frequency signals transmitted and received by the TPUs as the signals pass through the spacer and housing, as compared to the attenuation of the RF signal that results as it passes through the metal body of the drill pipe and through the drilling fluid flowing within the drill pipe. In the example of
Each spacer, together with its corresponding housing, operates to protect and isolate its corresponding TPU from the environment within the drill pipe, and provides a path for RF signals to be exchanged between the TPUs with little or no attenuation of said RF signals. Although the gap between the ends of the two wireless communication assemblies 450a and 450b (i.e., between the spacers and housings of each of the two drill pipes, shown exaggerated in the figures for clarity), and/or the gap between each spacer and the housing, may allow drilling fluid into the path of the RF signal, the level of attenuation of the RF signal that results can be maintained within acceptable limits for a given transmission power at least by limiting the size of the gaps. In at least some illustrative embodiments, such as shown in the example of
In at least some illustrative embodiments, power source 468 is a kinetic microgenerator that converts drill string motion and oscillations into electrical energy. In other illustrative embodiments, power source 468 is a kinetic microgenerator that converts movement of the drilling fluid into electrical energy. In yet other illustrative embodiments, power source 468 is a thermal microgenerator that converts thermal energy (i.e., thermal gradients or differences within and around the drill string) into electrical energy. Many other systems for providing electrical energy for recharging the batteries and providing power to wireless communication assembly 450 will become apparent to those of ordinary skill in the art, and all such systems are within the scope of the present disclosure.
As can be seen in the illustrative embodiment of
Continuing to refer to
As previously noted, transmitted RF signals suffer significant attenuation when passing through the metal drill pipe and through the drilling fluid within the drill pipe. This is due to the fact that when an RF signal passes through a material, the higher its conductivity (or the lower its resistivity), the higher the amount of energy that is transferred to the material, resulting in a corresponding decrease or attenuation in the magnitude of the RF signals that reach the RF receiver. Thus, the attenuation of the RF signal that reaches a receiver can be minimized by reducing the amount of RF energy that is propagated through materials with high conductivity. Such a reduction can be achieved or offset by: 1) reducing the distance that the signal traverses between the transmitter and the receiver; 2) using antennas at the transmitter, receiver, or both that provide additional gain to the transmitted and/or received signals; and 3) using antenna configurations and geometries that result in radiation patterns that focus as much of the propagated RF signal as possible through materials positioned between the transmitter and receiver that are transparent (i.e., have a very low conductivity, or are non-conducting and have a low dielectric dissipation factor) within the frequency range of the propagated RF signals. For example, some high temperature fiberglass plastics (i.e., fiber-reinforced polymers or glass-reinforced plastic), with working temperatures of 572° F.-932° F. and dielectric dissipation factors of 0.003-0.020, are suitable for use with at least some of the illustrative embodiments, as are some silicon rubbers with comparable dielectric properties.
The use of wireless data transmission at the pipe joints and wired data transmission within a drill pipe, as previously described and shown in
By focusing the beam along a path between the two antennas that is filled primarily or entirely with a radiotransparent material, the RF signal transmitted along the signal propagation path between the two TPU antennas is received with little or no attenuation by the receiving TPU. Also, by curving the antenna into a loop as shown in
Additionally, by improving the magnitude of the RF signal present at the receiving TPU, less power is needed (compared to at least some other existing downhole communication systems) both to transmit the RF signal and to amplify and process the received RF signal, for a given desired signal to noise ratio at the receiving TPU. This lower power consumption rate allows the TPU to operate for a longer period of time without having to shut down and allow the power source to recharge the batteries. In systems that do not incorporate a power source, the TPU can operate for a longer period of time without having to trip the drill string in order to charge or replace the TPU batteries (or replace a pipe segment with dead TPU batteries). Also, by improving the power efficiency of the system, higher data rates may be achieved (within the bandwidth limits of the system) for a given level of power consumption relative to existing systems (based on the premise that the higher operating frequencies needed for higher data transmission rates incur higher TPU power consumption).
The above discussion is meant to illustrate the principles of at least some embodiments. Other variations and modifications will become apparent to those of ordinary skill in the art once the above disclosure is fully appreciated. For example, although the embodiments described include RF transceivers that perform the modulating and demodulating of the transmitted and received RF signals respectively, other embodiments can include RF modules that only up-convert and/or down-convert the RF signals, wherein the processing logic performs the modulation and/or demodulation of the RF signals (e.g., in software). Further, although a simple single bus architecture for the processing module is shown and described, other more complex architectures with multiple busses (e.g., a front side memory bus, peripheral component interface (PCI) bus, a PCI express (PCIe) bus, etc), additional interfacing components (e.g., north and south bridges, or memory controller hubs (MCH) and integrated control hubs (ICH)), and additional processors (e.g., floating point processors, ARM processors, etc.) may all be suitable for implementing the systems and methods described and claimed herein. Also, although the illustrative embodiments of the present disclosure are described within the context of petroleum well drilling, those of ordinary skill will also recognize that the methods and systems described and claimed herein may be applied within other contexts, such as water well drilling and geothermal well drilling, just to name some examples. Additionally, the claimed methods and systems are not limited to drill pipes, but may also be incorporated into any of a variety of drilling tools (e.g., drill collars, bottom hole assemblies and drilling jars), as well as drilling and completion risers, just to name a few examples. It is intended that the following claims be interpreted to include all such variations and modifications.