Research And Design Of Long-Distance Communication System Between Downhole And Surface For Formation Testing

In order to quickly monitor the actual situation downhole and extract data such as downhole pressure and temperature during formation testing,it is necessary to study formation testing monitoring technology.This paper investigates the status quo of formation testing monitoring technology at home and abroad,studies the equivalent circuit model of single-core cable,and designs a set of downhole and surface longdistance communication systems.The system consists of two main parts,the downhole telemetry module and the surface telemetry module.At the same time,in order to facilitate the ground operators to read the test data,the ground host computer software is designed.Firstly,when studying the transmission characteristics of single core cable,establish its equivalent circuit model by using the micro element method.Then use the existing measurement tools to directly measure the three parameters of resistance R,inductance L,and capacitance C of a single-core cable with a unit of measurement of 100 meters.Afterwards,the equivalent circuit model is built by the Multisim14.0 simulation software,the single-core cable transmission is simulated,the transmission characteristics are studied,and the factors affecting the transmission efficiency are analyzed.Secondly,when designing the system,the transmission code type commonly used in today’s formation testing and logging systems is firstly studied and compared.Considering various aspects,the differential Manchester encoding is selected as the transmission code pattern.Finally,in the subsequent circuit design,the downhole module and the surface module are unified,and the same circuit structure is adopted,including the MCU main control module,the coding transmitter driver module,the coding receiver module.Since the ground end needs to communicate with the host computer,a wireless communication module based on ESP-12 F is specially designed.The coding and decoding of the collected data are all done in software in the MCU.The software design is completed through external interrupts,capture of rising and falling edges,and timers.Because the circuit structure is the same,this paper takes the ground telemetry module as an example to make a detailed introduction in chapters 3,4,5,and 6.After the design of the system is completed,based on the equivalent circuit model of the single-core cable studied before,a physical test platform is built to simulate the5500 m long-distance well-ground communication test.In the process of testing,the transceiver function between the wireless communication module and the host computer,the code sending and driving function,and the code receiving function are verified,which proves the feasibility of the system design.