Research On Coalbed Methane Well Test Monitoring System Based On Injection/Pressure Drop Method

Coalbed methane is an efficient and clean energy attached to the coal mining process,which is known as“gas”.The distribution of coalbed methane resources is wide,the volume is rich.When coalbed methane is mined,it is necessary to investigate the coal reservoir,which includes the mechanism of extracting coalbed methane,drilling technology,and obtaining key parameters of the coal reservoir.The well test technology is an important way to obtain key parameters of coal reservoirs.Therefore,this paper combines with the practical production technology of Shanxi Coal Geology Bureau and the innovative project “Coalbed Methane Injection / Pressure Research and development of ground control monitoring system for down test well,project number is 2017-5” to carry out research on well test technology.There are five common methods of coalbed methane well testing technology: the perfusion test method,the DST test method,the injection / pressure drop method,the slug test method,and the variable flow well test method.By comparing several common methods and in view of the low permeability in Shanxi coal reservoirs,this paper focuses on the study of coalbed methane injection / pressure drop method,and works on it based on a series of theoretical foundations.The injection stage is an important stage to carry out the injection / pressure drop method.Ensuring constant current injection is very difficult.It is also an urgent and practical problem.Currently,monitoring and controlling system is mainly performed manually.Therefore,it is of great significance to study the coalbed methane well test monitoring system.In order to study the coalbed methane well test monitoring system,this paper analyzes the signals involved in the use of the coalbed methane well test method based on the basic theory of the extraction mechanism,drilling process and well test method in the coalbed methane production process.It also analyzes the key flow and pressure,which are very important in the injection / pressure drop method.At the same time,the stable injection of liquid flow is an extremely critical operation in this process.Therefore,this research is based on the incremental PID control algorithm to measure and control the injected flow and pressure.It also designs the overall system according to the actual site requirements,including device selection,the design and production of the circuit,and programming of upper computer and lower computer.The serial port connection method is carried out to realize the communication between the upper computer and the lower computer.The combination of software and hardware is used to build an experimental platform to realize the measurement and control of the coalbed methane well test monitoring system.The experimental results show that the coalbed methane well test monitoring system designed in this paper can realize the real-time monitoring of key parameters and guarantee constant current injection in a certain range with high accuracy.It has certain ability to prevent the external interference in this paper.The system is finally checked and accepted by expert group.This system has guiding significance for the development of coalbed methane well test monitoring technology and the development of coalbed methane mining in Shanxi Province.