The Design And Development Of Separate Layer Water Injection Flow Measurement And Control System

Separate layer water injection is an effective way to improve oil recovery rate,decrease interference and maintain long-term stable yield.Eccentric water injection used in oilfield at present has some problems: high cost in equipment maintenance,low measuring precision,heavy workload in regulation and it's unable to control flow automatically.In order to solve these problems,this paper presents a new flow measurement and control system combing with technological requirements.The system can measure parameters of injection layers in real-time and also can regulate motor,control opening of water nozzle using an improved PID control algorithm to regulate flow of every layer.The specific work in this paper is as follows:According to high temperature,high pressure,strong corrosion and small spaces in the underground and other adverse factors,this paper designs the whole scheme of separate layer water injection flow measurement and control system with technological requirements.Based on piezoresistive pressure sensor's sensitive characteristic to pressure and temperature,the system realizes the simultaneous measurement of pressure and temperature by using one pressure sensor and without temperature sensor.A simultaneous measurement model of temperature and pressure is established by analyzing the principle and analyzing the experimental data with regression analysis method.This design can decrease space,reduce cost and simplify installation requirements on the premise of meeting the pressure and temperature measurement accuracy.Differential pressure flowmeter is used to measure flow according to water injection technology and water injection rate requirements.The best hole dimensions of throttling element under different flow for three different diameter pipes are established by the simulation with Fluent.Flow correction model is given through analyzing the effect of temperature and tilt angle on flow measurement.Software and hardware of flow measurement and control system are designed.Hardware design including power supply circuit,measuring circuit and flow control circuit is at the core of control chip dsPIC33 F with considering high temperature,high pressure,small space and other factors of underground environment.Data acquisition,flow calibration and motor control are realized by software.Improved PID control algorithm is used to control motor once flow deviation exceeds the control zone which can reduce motor motion and prolong its life.Downhole-control-mode and ground-control-mode are set in this system,which make the field control more flexible.This system has passed tests in simulation well and achieved the expected effect.Pressure measurement accuracy is 0.5%FS,temperature measurement accuracy is ±0.5 ?;flow measurement accuracy is 3%FS and flow control error is less than 5%.