Design And Development Of A Constant Temperature Differential Thermal Flowmeter With Sensor Array

The fluid production and flow rate of oil has generally decreased(less than 5m3/day)with continuous exploitation of oil wells in China.Meanwhile in order to enhance oil recovery and increase production,more horizontal wells and highly deviated wells are developed in the country.While traditional flowmeters can not meet the demands of low flow rates fluid in horizontal wells and highly deviated wells because they are only applicable for point measurement in high-yield fluids in vertical wells.Thus,in view of the current domestic logging requirements at home,it has a great significance to study a method suitable to monitor dynamically low flow rate of low production fluid,design and develop an array flow detection instrument for developing sustainably of domestic old oil well.The thermal flow detection method based on the principle of thermal forced convection becomes a new solution in domestic downhole flow measurement of lowyield liquids because it is sensitive to low flow rates.At present,thermal flowmeter is mainly used to measure low velocity gas mass flow on surface engineering.And there has been a single channel thermal flow detection scheme existing based on the constant power measurement method in my laboratory in the early phase.On the basis,by analyzing the current actual logging needs and the shortcomings of the traditional flowmeters,an implementation scheme of array detection instrument based on the constant temperature differential thermal flow measurement method suitable for downhole environmental is proposed in the paper through literature review.According to the scheme,in order to sensitively respond to the tiny change of fluid temperature and meet the demand of multi-point flow measurement,a high-precision sensor array struct is designed to measure the flow of six channels.An acquisition controller based on FPGA and a constant temperature difference controller based on DSP are designed to realize multi-channel data acquisition and heating voltage adjustment respectively in real time.And a prototype of array constant temperature differential thermal flowmeter is developed by designing the hardware circuit and the software control logic.And a series of measurement experiments are carried out in simulation wells to test the response characteristics to flow rate of the instrument.The experimental results show that:(1)The resolution of the flowmeter can reach at least 1m3/day in the flow range of 0?15 m3/day.And it has the characteristics of low measurement limit and high resolving ability.(2)For the flux variations,the response law about the heating power of 6 channels is almost same.Hence the measurement consistency is good,which meets the needs of array flow detection in horizontal wells and highly deviated wells.It solves the problems traditional flowmeters face about measuring flow rate accurately in such oil wells.In addition,the high integrated circuit and the small volume of the instrument meet the requirements of downhole environment.Therefore,the array constant temperature differential thermal flowmeter designed and developed in this paper basically meets the current flow measurement needs in domestic low-yield horizontal wells and highly deviated wells,and has important reference value for the development and research of related logging tools in China.