Apparatus and method for acoustic telemetry measurement of well bore formation debris accumulation

Abstract

An invention is claimed wherein the signal loss along steel drill pipe walls can be estimated in the absence of a loss mechanism due to the formation debris at various positions in the well bore; the signal loss in excess of the calculated attenuation is generally and directly attributable to the build-up of said formation debris and an estimation of the amount can be determined. Furthermore, by use of distributed acoustic nodes positioned in the well between the transmitter in the BHA and the surface receiver—configured as repeaters—the formation debris build-up can be determined in each section so defined. This new information enables the driller to implement hole cleaning means in a timely manner and as appropriate, thus avoiding the problems of getting stuck in the hole, and possible well abandonment. An extension of the method enables the hole cleaning process to be automated, thereby improving efficiency.

1 . A system for measuring formation debris accumulation in a wellbore, comprising:
 an acoustic telemetry transmitter disposed at a first location on a drill string,   an acoustic telemetry receiver disposed at a second location on the drill string spaced from the first location or at a third location on the surface, and configured to receive an acoustic signal sent along the drill string from the transmitter via a wall of the drill string, and   a processor communicative with the receiver and having a memory storing information comprising: an amplitude of an acoustic signal launched by the transmitter, and parameters related to the properties, motion, and inclination angle of a drill-string section between the transmitter and receiver, the memory further encoded with instructions executable by the processor to use the stored information and an acoustic signal transmitted by the transmitter and received by the receiver, to calculate an intrinsic signal level loss along the drill string section between the transmitter and receiver, an actual signal level loss of the transmitted acoustic signal, and the difference between the actual signal level loss and intrinsic signal level loss.   
     
     
         2 . A system as claimed in  claim 1  wherein the acoustic telemetry transmitter is a bottomhole assembly transmitter located in a bottomhole assembly of the drill string. 
     
     
         3 . A system as claimed in  claim 2  further comprising a bottomhole assembly processor in communication with the bottomhole assembly transmitter and having a memory encoded with information comprising at least one of: an amplitude of an acoustic signal launched by the bottomhole transmitter, and parameters related to one or more of the properties, motion, and inclination angle of a drill-string section between the bottomhole transmitter and the receiver, the memory further encoded with instructions for the bottomhole transmitter processor to cause the bottomhole transmitter to transmit this information to the receiver. 
     
     
         4 . A system as claimed in  claim 2  further comprising a surface transmitter communicative with the processor and located at surface, and wherein the acoustic telemetry receiver is a surface receiver located at surface and the processor is further programmed to cause the surface transmitter to transmit a control signal to the bottomhole assembly when the difference between the actual and intrinsic signal level losses exceeds a threshold value. 
     
     
         5 . A system as claimed in  claim 1  further comprising a plurality of telemetry nodes, and wherein the transmitter is a part of a first node, and the receiver is part of a second node, and the drill string section is between the first and second nodes. 
     
     
         6 . A system as claimed in  claim 5  wherein at least one node further comprises a sensor for measuring the inclination angle of a drill string section in the vicinity of the node. 
     
     
         7 . A system as claimed in  claim 4  further comprising one or more telemetry nodes each disposed on the drill string between the surface receiver and the bottom hole assembly transmitter, at least one of the nodes comprising a node receiver configured to receive acoustic signals sent along the drill string from another node or from the bottom hole assembly transmitter, and a node transmitter for transmitting an acoustic signal along the drill string to the surface receiver. 
     
     
         8 . A system as claimed in  claim 7  wherein the at least one node further comprises a node processor in communication with the node transmitter and node receiver and having a memory encoded with information comprising at least one of: an amplitude of an acoustic signal launched by a transmitter of another node or by the bottomhole assembly transmitter, and parameters related to one or more of the properties, motion, and inclination angle of a drill-string section in the vicinity of the node, the memory further encoded with instructions for the node processor to cause the node transmitter to transmit this information. 
     
     
         9 . A system as claimed in  claim 8  wherein the memory of the node processor is further encoded with instructions for the node processor to calculate the intrinsic signal level loss along the drill string section in the vicinity of the node, the actual signal level loss of an acoustic telemetry signal received by the node receiver which was transmitted across the drill string section in the vicinity of the node, and the difference between the actual signal level loss and intrinsic signal level loss across the drill string section in the vicinity of the node, and to cause the node transmitter to transmit this information. 
     
     
         10 . A system as claimed in  claim 9  wherein the node transmitter is configured to transmit an acoustic signal containing the difference between the actual signal level loss and intrinsic signal level loss across the drill string section in the vicinity of the node to the surface receiver, and the surface processor is further programmed to cause the surface transmitter to transmit a control signal to the bottomhole assembly when the difference between the actual and intrinsic signal level losses as calculated by the node processor exceeds a threshold value. 
     
     
         11 . A system as claimed in  claim 9  wherein the memory of the node processor is further encoded with instructions executable by the node processor to cause the node transmitter to transmit a control signal to the bottomhole assembly when the difference between the actual and intrinsic signal level losses across the drill string section as calculated by the node processor exceeds a threshold value. 
     
     
         12 . A system as claimed in  claim 11  wherein the memory of the node processor is further encoded with instructions executable by the node processor when the threshold value is exceeded to cause the associated node transmitter to acoustically transmit motor control instructions selected from the group consisting of: changes to drill bit rotation speed, drill bit angle, weight on bit, and flow rate control. 
     
     
         13 . A system as claimed in  claim 1  wherein the process calculates the actual signal loss by subtracting the amplitude of the acoustic signal launched by the transmitter as stored in the memory from the amplitude of the acoustic signal as received by the receiver. 
     
     
         14 . A method for measuring formation debris accumulation in a wellbore, comprising:
 determining an amplitude of an acoustic signal launched by an acoustic telemetry transmitter disposed at a first location on a drill string, and parameters related to the properties, motion, and inclination angle of a drill-string section between the transmitter and an acoustic telemetry receiver disposed at a second location on the drill string spaced from the first location or at a third location on the surface;   receiving by the receiver an acoustic signal transmitted by the transmitter;   calculating an intrinsic signal level loss along the drill string section between the transmitter and receiver from the determined parameters,   calculating an actual signal level loss of the transmitted acoustic signal from the received acoustic signal and the determined amplitude of the acoustic signal launched by the transmitter, and   calculating the difference between the actual signal level loss and intrinsic signal level loss.