Development Of Low Liquid Yield Detector With Constant Temperature Difference Based On Heat Conduction

Accurate detection of small flow has become a technical problem to be solved urgently in domestic low permeability oil fields,because the traditional liquid flow meter has the shortcomings of low sensitivity,poor repeatability and low resolution in small flow detection of low permeability oil fields.In this paper,the principle of heat conduction and measurement principle of thermal flowmeter are studied theoretically.The detection system of low fluid production was established based on thermostatic difference method;an incremental PID control algorithm is designed to realize the closed-loop control of the heating power to maintain a constant temperature difference;TMS320F2808,which has fast data operation speed and low power consumption,is used as the main control chip to ensure rapid flow measurement.This topic combined with the oil field small flow can not accurately detect the problem,developed a new type of thermal low yield liquid detector.(1)The paper analyses the oilfield downhole flow testing instrument working principle,the advantages and disadvantages of existing in view of the oilfield at present to solve the problem of small flow measurement,is proposed based on the principle of heat conduction is constant temperature difference method of small flow measurement method,designed speed sensor and temperature sensor,established the mathematical model of the heating voltage and flow speed sensor,The hardware circuit design of the detector is carried out.(2)Designed and debugged the circuit and software of the thermal low-yield liquid detector.The software and hardware of the system adopt the modular design idea,the circuit module is mainly divided into the power module,the cable bus driver module,the data processing module,the analog signal acquisition module and the heating voltage control module.The system software mainly realizes the acquisition,processing and operation of data,and establishes the encoding,decoding and communication of signals.The communication of instrument bus adopts DDL3 mode which is commonly used in well logging instrument and has strong anti-jamming ability.The main program modules include GPIO initialization module,AD conversion module,SPI communication module,data transmission module and PID control module.(3)The performance of constant temperature difference low-yield liquid detector was verified through experiments.By building an indoor flow calibration test platform,two low-yield liquid detector prototypes were manufactured,and the laboratory high temperature test,vibration test,impact test and flow calibration test were carried out on the prototypes to test the technical indexes and performance of the instruments,and the field injection well test was completed in Dong X Well,Changqing Oilfield.The test results show that the instrument has high repeatability,sensitivity and resolution for the detection of small flow rate of 1?10m~3/d.