Abstract:
In one aspect of the present invention, a method for tool string communication comprises the steps of providing a downhole tool string with at least two downhole LWD/MWD instruments in electrical communication with a downhole telemetry system. The instruments are capable of generating at least one data packet assigned a priority. The tool string is deployed in a wellbore and then the priority of the data packet is changed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in-part of U.S. patent application Ser. No. 12/109,211 filed on Apr. 24, 2008, which is now U.S. Pat. No. 8,061,443 issued on Nov. 22, 2011, and entitled Downhole Sample Rate System. This application is herein incorporated by reference for all that it discloses. 
    
    
     BACKGROUND 
     Knowledge of downhole parameters and conditions help drillers make decisions that may increase drilling efficiency and save money. Downhole data acquisition systems may be used by drillers to determine those parameters, such as spatial position, formation type, and the economic potential of a resource. Often, bottom hole assemblies (BHA) will contain sensors that can measure various rock and drilling properties employing acoustic, nuclear, electromagnetic, and other sensing and data acquisition capabilities. At different points in a drilling operation, data from certain sensors may be of a higher interest then data from other sensors. 
     U.S. Pat. No. 5,959,547 to Tubel et al., which is herein incorporated by reference for all that it contains, discloses a plurality of downhole control systems interconnected by a network including a server for monitoring and controlling network communications. Each downhole control system is associated with a zone in one or more wells. The downhole control systems communicate directly with each other transferring information and commands as necessary. The downhole server monitors network communications to resolve data collisions and provides supervisory functions. 
     U.S. Pat. No. 6,909,667 to Shah et al., which is herein incorporated by reference for all that it contains, discloses several methods for selecting and transmitting information from downhole source using more than one channel of communication wherein data streams transmitted over each communications channel are each independently interpretable without reference to data provided over the other of the communications channels. Preferred embodiments incorporate the use of a combination of at least two of mud-based telemetry, tubular-based telemetry, and electromagnetic telemetry to achieve improved results and take advantage of opportunities presented by the differences between the different channels of communication. 
     U.S. Pat. No. 7,142,129 to Hall et al., which is herein incorporated by reference for all that it contains, discloses, a method and system for use in synchronizing at least two clocks in a downhole network. The method comprises determining a total signal latency between a controlling processing element and at least one downhole processing element in a downhole network and sending a synchronizing time over the downhole network to the at least one downhole processing element adjusted for the signal latency. Electronic time stamps may be used to measure latency between processing elements. The system for electrically synchronizing at least two clocks connected to a downhole network comprises a controlling processing element connected to a synchronizing clock in communication over a downhole network with at least one downhole processing element comprising at least one downhole clock. Preferably, the downhole network is integrated into a downhole tool string. 
     BRIEF SUMMARY 
     In one aspect of the present invention, a method for tool string communication comprises providing a downhole tool string with at least two downhole Logging While Drilling (LWD)/Monitoring While Drilling (MWD) instruments in electrical communication with a downhole telemetry system. The instruments are capable of generating at least one data packet assigned a priority and tool string is deployed in a well bore. The priority of the data packet is then changed. 
     The priority may be changed at the point of creation by activating or deactivating the instruments. The priority may also be changed by adjusting a preamble before the data in a communication packet. The priority may be changed by adjusting the channel in which the data is sent. The priority may be changed by adjusting the order in which data is sent. Multiple data packets may have the same priority. Data packets may each have a unique priority. Data packets may have either a high priority or a low priority. 
     The priority may be changed remotely or onsite by either a computer or a human user. The priority may also be changed by a downhole instrument, such as a downhole processing unit. Data packets of a lower priority may be filtered out by a downhole processing unit. Data packets of a lower priority may be stored within the tool downhole for later transmission or sent up in unused or latent transmission time and stored uphole for later use. Data packets of a lower priority may be erased downhole. The priority may be automatically changed when the instruments sense that a downhole condition deviates from a pre-determined threshold window. Priority may also include the need to take more measurements per unit time or per unit distance from a first tool in preference to taking measurements from a second or a third tool. The priority may be changed in real-time or near real-time. The priority may be changed in response to a change in downhole geology, particular downhole drilling condition; some downhole or uphole activity or condition, response to results from some processed or interpreted data or change in desired outcome or goal. 
     For the purposes of this disclosure, the terms LWD and MWD refers to “logging-while-drilling” and “measurements-while-drilling” respectively. These terms refer to measuring the physical properties of formation and/or well bore, conditions of the well bore and/or drilling tools or combinations thereof, while advancing the drill string in the well bore, shortly there after, or while the drill string is still deployed in the well bore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional diagram of an embodiment of a downhole tool string. 
         FIG. 2  is a cross-sectional diagram of an embodiment of tool string component. 
         FIG. 3  is a block diagram of sensors in communication with an up-hole computer. 
         FIG. 4  is another block diagram of sensors in communication with an up-hole computer. 
         FIG. 5   a  is a cross-sectional diagram of a downhole telemetry system. 
         FIG. 5   b  is a block diagram of a downhole telemetry system. 
         FIG. 6  is a cross-sectional diagram of a mud pulse system. 
         FIG. 7   a  is a block diagram depicting a priority communication sequence. 
         FIG. 7   b  is another block diagram depicting a priority communication sequence. 
         FIG. 7c  is another block diagram depicting a priority communication sequence. 
         FIG. 7d  is another block diagram depicting a priority communication sequence. 
         FIG. 8   a  is a plot depicting a communication priority system. 
         FIG. 8   b  is a depiction of a data packet. 
         FIG. 9  is another block diagram of sensors in communication with an up-hole computer. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , a downhole tool string  101  may be suspended by a derrick  102 . The downhole tool string  101  may comprise one or more downhole components  100 , linked together in the downhole tool string  101  and in communication with surface equipment  103  through a downhole telemetry system. Some telemetry systems may enable high-speed communication between devices connected to the downhole tool string  101 , and may facilitate the transmission of data between sensors and sources. The data gathered by the downhole components  100  may be processed downhole, may be transmitted to the surface for processing, may be filtered downhole and then transmitted to the surface for processing, may be compressed downhole and then transmitted to the surface for processing, or combinations thereof. As an example, the downhole components  100  may include resistivity tools  106 , seismic tools  104 ,  115 , nuclear tools  107 , thermometers, pressure sensors, rheology sensors, acoustic sensors, chemical sensors, calipers, formation hardness sensors, strain gauges, vibration sensors, pressure sensors, tool diagnostic sensors, electrical potential sensors, RPM sensors, WOB sensors, drill string stability sensors, fatigue sensors, and annular pressure sensors. 
     As the downhole tool string  101  advances, different rock formations  111 ,  112 ,  113 ,  114  may be encountered. Changes in formation type and depth give cause to change the dynamic conditions of the drill string as well as a level of interest an observer may address to sensor information from certain intervals or formation types. Reaching a drilling target, reaching a formation of interest, or encountering a particular drilling condition may result in a shift in drilling goals as determined by surface operator or even a departure from pre-drill plans. Thus a priority assigned to data packets generated by certain sensors may need to be adjusted to best meet the needs of the downhole or uphole situation. Different sensor readings may be of higher interest based upon the formation geology proximate the drill bit  109  or those sensor readings that may best describe the current BHA location, situation, and condition mitigation. 
       FIG. 2  depicts a cross-sectional diagram of an embodiment of a sensor  201  in communication with a processing unit  202 . The processing unit  202  is in communication with a downhole telemetry system  206 . A preferred downhole telemetry system is disclosed in U.S. Pat. No. 6,670,880 to Hall, which is herein incorporated by reference for all that it discloses. In the embodiment of  FIG. 2 , the sensor  201  is disposed within a sleeve  203  that encases a drill pipe mandrel  205 . A pocket  204  exists between the sleeve  203  and the mandrel  205 . The pocket  204  may contain processing units, telemetry devices, or other necessary components. The processing unit  202  may perform data analysis functions and communication functions. The processing unit  202  may change the priority of data packets from certain sensors based upon its analysis. The processing unit  202  may change the priority of data packets from certain sensors based upon commands received from an up-hole computer. 
       FIG. 3  is a block diagram depicting an embodiment of a downhole telemetry system in communication with sensors  312 . In the depicted embodiment, an acoustic sensor  307 , a resistivity sensor  308 , a nuclear sensor  309 , a temperature sensor  310 , and a pressure sensor  311  are all connected to a router  306 . The depicted case should not be considered a limiting case, in as much as a variety of sensors  312  or tools may be connected to the router  306 . The router  306  serves the function of facilitating communication between a plurality of sensors and a processing unit  304 . In some embodiments the router  306  may be a multiplexer. 
     The router  306  is in communication with a buffer  305 . The buffer  305  provides memory for data packets to reside in while they wait for processing. The buffer  305  may be first in first out (FIFO) memory. The buffer  305  is in communication with the processing unit  304 . The processing unit  304  may perform a variety of functions. The processing unit may perform preliminary analysis on the data packets that it receives. The processing unit may perform prioritizing functions on the data packets. Analysis may lead the processing unit  304  to increase or decrease the sample rate of certain sensors  312  based upon the priority assigned to the data packets generated by those certain sensors  312 . A clock  303  is in communication with the processor  304 . This clock  303  may be synchronized with an up-hole clock. The prioritizing functions may be determined by communications from up-hole users or computer. The prioritizing functions may be determined by the processing unit  304  analyzing the data packets. 
     Prioritizing functions may be implemented in a variety of ways including but not limited to those discussed in this disclosure. The processing unit  304  may send data packets from certain sensors  312  of higher priority more frequently than those of lower priority, or the processing unit  304  may decide to ignore lower priority data packets and only send higher priority data packets. Either of these methods may be implemented by deleting or filtering out all lower priority signals, by turning off the sensors  312  that are generating the lower priority data packets, or by storing the lower priority data packets downhole and sending them later. Turning certain sensors  312  off that are generating lower priority data packets may have the added benefits of reducing power usage at desired times, or during delays in drilling, or for time delay sampling. 
     The processing unit  304  is in communication with a network sub  302 . The network sub  302  may contain signal amplifiers. A plurality of network subs  302  may exist within the same drill string. More than one network sub may be in communication with sensors  312  or tools. The network sub is in communication with an up-hole computer  301 . The up-hole computer  301  may be operated by a human user or it may be automatic. The up-hole computer  301  may be remote. 
       FIG. 4  is a block diagram depicting another embodiment of a downhole telemetry system in communication with sensors  312 A. In this embodiment each sensor  312 A is in communication with a unique processing unit  304 A. The processing units  304 A in this embodiment may perform data packet analysis and priority functions on the data packets that they each receive. The data packets&#39; priority in this embodiment would predominantly be determined by an up-hole computer  301 A or human user. The up-hole computer  301 A may assign each unique processing unit  304 A a priority to assign its data packets. The up-hole computer A or human user could adjust priority assignments sent to each unique processing unit  312 A based on need. In this embodiment each processing unit  304 A may be able to perform priority operations on the data packets that it receives. The processing units  304 A may be programmed to test for certain thresholds. Once a sensor  312 A reading reaches a predetermined threshold the sensor&#39;s  312 A accompanying processing unit  304 A may be able to automatically adjust the priority of the data packet. The adjusted priority may influence the sampling rate of certain sensors  312 A at the expense of others, depending on available bandwidth. The processing units  304 A may have a clock  303 A in common. The clock  303 A may be synchronized with an up-hole clock as previously disclosed. The processing units  304 A may all be in communication with a single memory unit  401 . The memory unit  401  may be accessible by each individual processing unit  304 A. Each processing unit  304 A may be able to manage the single memory unit  401  appropriately to ensure that the data packets are transmitted in the correct manner based on priority. 
       FIG. 5   a  is a diagram of embodiments of a downhole components. In the depicted embodiment, communication cables  501 A,  501 B runs the length of each drill pipe  502 A,  502 B, respectively. The communication cable  501 A is connected to at least one inductive coupler  503  at both ends of pipe  502 A. The data signals transmitted on the communication cable  501 A generate a magnetic field which transfers the data signal to a corresponding magnetic ring (not shown) in an adjacent drill pipe  502 B. This process repeats throughout the drill string  101 A.  FIG. 5   b  is a block diagram depicting an embodiment of a downhole telemetry system  507 . Using the components described in  FIG. 5   a , the data signals may require amplification along the drill string  101 A. This amplification may take place within network subs  508  that are part of the drill string  101 A. The network subs  508  may occur at every pipe length or may occur periodically after several pipe lengths. 
       FIG. 6  is a diagram of an embodiment of a mud pulse telemetry system  600 . The drill string  101 B contains a mud pulse generator  603 . These are both in communication with on up-hole mud pulse unit  605 . The up-hole mud pulse unit  605  is able to receive data from and communicate commands to downhole tools  602 . The mud pulse generator  603  may be in communication with downhole processing units. The downhole processing units control the downhole sensors and downhole tools  602 . In this embodiment commands may be sent through mud pulses to adjust the priority of the data packets that are being sent. The priorities could also be adjusted by the downhole processing units. 
       FIG. 7   a  and  FIG. 7   b  are diagrams depicting an embodiment of a priority operation.  FIG. 7   a  depicts a data stream of a sequence of data packets  700 A. The data packets  700 A are each associated with a sensor that generated them. Sensor A generates packet  701 , sensor B generates packet  702 , sensor C generates packet  703 , and sensor D generates packet  704  respectively. In this embodiment, the data packets  700 A may all have the same priority such that they are being transmitted in the order they were received by a downhole processing unit. The data packets  700 A in this embodiment may also have unique priorities wherein the data packets  700 A are transmitted in order of priority.  FIG. 7   b  depicts the sequence of data packets  700 A from  FIG. 7   a  after a priority was changed resulting in an altered sequence of data packets  700 B. In this embodiment, the data packets  702  generated by sensor B were adjusted to a lower priority. The lower priority is manifested by data from sensor B no longer being sent. This could be implemented by turning sensor B off, by erasing the data from sensor B by saving the data from sensor B for later transmission, or by filtering out the data from sensor B. 
       FIG. 7   c  and  FIG. 7   d  are diagrams depicting another embodiment of a priority operation.  FIG. 7   c  depicts a data stream of a sequence of data packets  700 C. The data packets  700 C are each associated with a sensor that generated them. Sensor A generates packet  701 , sensor B generates packet  702 , and sensor C generates packet  703  respectively. In this embodiment, all of the data packets  700 C in  FIG. 7   c  may have the same priority.  FIG. 7   d  depicts the sequence of data packets  700 C of  FIG. 7   c  after some data packet priorities are adjusted resulting in an altered sequence of data packets  700 D. The change in data packet priority is manifest through a change in sample rate. In the embodiment depicted in  FIG. 7   d , packet  702  generated by sensor B has a higher priority than packet  703  generated by sensor C, which is implemented by sampling sensor B twice as often as sensor C. In this embodiment, packet  701  from sensor A has a higher priority than packet  702  from sensor B, and packet  703  from sensor C. This is implemented by sampling sensor A three times as often as sensor C and one and a half times as often as sensor B. 
       FIG. 8   a  and  FIG. 8   b  depict embodiments of data packets  1050 . In  FIG. 8   a , the data packets  1050  are sent at different frequencies. Data packet priority is determined by the frequency channel  1051  that the packet is sent in. In this embodiment, three channels  1051  are depicted. In  FIG. 8   b , a data packet  1050  is depicted with a preamble  1052 . In this embodiment the data packet priority is determined by information stored in the preamble  1052 . In both of these embodiments, the data packet priority could be adjusted by either changing the frequency channel that the data packet is in or by adjusting the information stored in the preamble  1052 . 
       FIG. 9  is a block diagram depicting an embodiment of a downhole telemetry system in communication with a processing unit  304 E. In this embodiment, the processing unit  304 E comprises a central processing unit (CPU)  902  and a memory component  903  with a priority module  904 . In other embodiment, the processing unit  304 E may comprise a field-programmable gate array (FPGA). The processing unit  304 E is in communication with a clock  303 E. The clock  303 E may be synchronized with a clock from an up-hole computer  907 . The processing unit  304 E is in communication with a network sub  302 E. The network sub  302 E may comprise amplifiers. A drill string may comprise a plurality of network subs  302 E spaced periodically along the distance of the drill string. The processing unit  304 E is in communication with a buffer  305 E which stores data packets waiting processing. The buffer  305 E is in communication with a router  306 E. The router  306 E serves the function of facilitating communication between a plurality of instruments and the processing unit  304 E. The router  306 E may be in communication with sensors  312 E, a lower sub  906 , or various drill string tools  905 . 
     The processing unit  304 E may analyze data packets that it is receiving. The CPU  902  may function as a data analyzer, priority assigner, or priority adjuster. The CPU  902  in analyzing data packets from lower subs  906  and also from its sensors  312 E may adjust the priority of various data packets. The CPU  906  may receive commands from the up-hole computer  907  to adjust data packet priorities. The CPU  902  transmits data to a memory component  903 . The memory component  903  acts as a queue, storing data packets waiting to be transmitted to the next sub  302 E. The memory component  903  includes a priority module  904 . The priority module  904  maintains the queue in order of data packet priority. The priority module  904  may have the abilities to erase data packets or to move data packets to another place in the queue. 
     Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.