Simulation Of Drilling Information Transmission Channel Characteristics

Measure While Drilling(MWD) information transmission system is necessary part ofmodern drilling. The implementation of the drilling operations require to obtain downholeannular pressure, bottom hole temperature and wellbore trajectory and so on data correctly.Those information can be obtained through numerous sensors which are installed near the drillbit, and then are sent to the ground by surface and downhole two-way informationtransmission system for analyzing, evaluating formation, guiding drilling，predicting oil andgas reservoirs and recovery ratio. The method of MWD information mainly include Mud pulse,electromagnetic, intelligent drill pipe and acoustic telemetry. To evaluate these methods, theacoustic telemetry was selected to research deeply owing to these merits as low cost, high datatransfer rate, interference-free by the drilling fluid, and convenient to realize long-distanceinformation transmission with relays.Based on the transfer theory of acoustic along the drill strings, the drill strings channel istime-varying, its transmission characteristics is closely related to the composition of drillstring. A variety of drill string combination of acoustic channel characteristics are necessary tobe researched for acoustic two-way transmission along the drill strings channel. So the digitalfilter and the establishment of acoustic reflectionless transfer models (ARTM) are proposed tocreate the single drill string ARTM. With all kinds of ARTMs, the actual drill string channelcan be decomposed into varieties of known cascade of a single drill transmission model, andthe digital filter design and simulation were realized. Then based on the actual drill pipeparameters, one of drill string acoustic transmission characteristic of the channel wassimulated, and also on the foundation of that simulation channel, sound waves transmitted inthe channel using the common digital modulation and demodulation method was given.Finally analysis like acoustic transmission data rate, error rate, SNR based on the simulationconditions and the results are studied together, which will provide testing and inspectionplatforms for the research and testing of acoustic transmission instruments.