ZT-175 measurement while drilling system, is used for high temperature and high pressure well drilling , perform real-time measurement and transmission of borehole trajectory parameters. Compared with the ordinary ZT-MWD system, the ZT-175 system can measure all parameters of the ordinary MWD in higher downhole temperature and pressure. The downhole system mainly includes high temperature pulse module, transmission module, measuring module and gamma module.the system is fully compatible with the same type of imported products.

ZT-175 measurement while drilling system, is used for high temperature and high pressure well drilling , perform real-time measurement and transmission of borehole trajectory parameters. Compared with the ordinary ZT-MWD system, the ZT-175 system can measure all parameters of the ordinary MWD in higher downhole temperature and pressure. The downhole system mainly includes high temperature pulse module, transmission module, measuring module and gamma module.the system is fully compatible with the same type of imported products.

(1).Borehole trajectory measurement: Probe measure the values of accelerometers, fluxgates and temperature sensor, and calculate the borehole trajectory parameters.

(2).Encoding: According to the operating requirements, probe use fixed format or non fixed format to generate the electrical pulses. And then these electrical pulses transferred to pulser.

(3).Power generating: Pulser use the power transferred from impeller to generate electric energy.

(4).Transmission: Pulser generates positive pressure signals under the control of electrical pulses.

(5).Decoding: Transducer acquires the pressure signals generated by downhole system, the signals are transferred through barrier box and DAQ system to surface system. Then surface system decode the signals to real time parameters.

1 High Temperature Pulser:

l  Turbine generator :  The internal electromagnetic induction generate electricity by high-speed rotating Impeller , which is drived by the mud in the pipe . The electricity can be used for all downhole tools;

l  Positive pulse transmission: The signal is transmited by mud , pressure in the pipe is changed by the movement of poppet on the top of the pulser.

 2 Telemetry Module

l  Positive pulse data encoding:  the circuit encode manchester code to the pulser, support 0.5-3.0 bit / s rates and support three different rates switching.

l  Custom defined string : According to the requirements of different uses, provide a more flexible function to combine measurement parameters. Improve work efficiency by transmitting the most concerned data in the drilling progress;

l  Downhole measurement data storage .

3 Direction Module

l  Borehole trajectory measurement: The tool contains three axis accelerometer sensor, three axis flux-gate magnetometer sensor, temperature sensor.  Use 175℃ high performance processor to perform accurate measurement and calculation of the parameters include inclination, azimuth, and toolface(magnetic and gravity). Use advance temperature compensation model to eliminate the influence of high temperature. 

l  Toolface offset automatic measurement and correction.  This function avoid error of manual measurement.

4 Gamma Module

l  Measurement natural gamma ray by 3 sets of Geiger-Miller tube , automatic calculation of combined gamma ray;

l  The circuit uses 1553 bus interface, automatic management of high voltage power supply, ultra low power consumption;

5 Surface Data Processing System:

l  The real-time data processing:        Using high-speed data acquisition card to obtain the data of pressure sensor, providing to the computer to complete the analysis processing. Using  1553 bus interface card to communicate with downhole instrument.

l  Safety control system .  All sensors on the well floor ,included DDU, is connected through the safety barrier to isolate power supply and communication, as the requirements of petroleum.