Coalbed Methane Gas Underbalance Pressure Drilling Pressure Monitoring And Control System Research

Coalbed methane is a kind of clean energy source which includes methane as the main component. It is also a kind of unconventional natural gas which reservoir in the seam with an adsorption state, its occurrence and specialties determines that the development of technologies and processes of coalbed methane are different from conventional natural gas. According to the low mechanical strength and ease to collapse and crush characteristics of coal reservoir, coalbed methane is usually mined by multilateral horizontal underbalanced drilling technology in current time. It takes use of cave shaft gas injection way to realize the under-balanced drilling in coal seam, lower coal reservoir damage, penetration rate improving, effectively control of leakage, and reducing and avoiding underground complex situation like differential pressure sticking.In coalbed methane inflatable underbalanced drilling process, because of the underground varieties and uncertainties, the precise and real-time control of bottom hole pressure becomes the key factor to success for drilling construction. At present, overseas has formed the related technologies and accessory equipments for the real-time monitoring of bottom hole pressure of coalbed methane inflatable underbalanced drilling. Those are able to realize the accurate measurement and precise control of bottom hole pressure of underbalanced drilling in the process of drilling. While the domestic pressure monitoring technology for CBM inflatable underbalanced drilling is still in the experimental stage.According to the existing CBM inflatable underbalanced drilling process and field equipment, this paper puts forward a set of design solution of pressure monitor and control system which can satisfy the precise real-time control of the bottom hole pressure in CBM inflatable underbalanced drilling process. It also selects the pressure monitoring and control parameters, builds the data acquisition system based on distributed data acquisition methods, develops the real-time monitoring software system based on configuration software, establishes the fine control system based on throttling back pressure control model and the control system based on the vertical wells gas injection control model. With the application of expert PID controller in MATLAB, it makes a dynamic simulation for throttling back pressure control system. With the configuration software, it realizes the real-time control of the two control parameters of vertical well gas injection control system, gas injection note and pressure.CBM inflatable underbalanced drilling pressure monitoring and control system set the real-time data acquisition, real-time monitoring and control as a whole, it can provide the strong technical support for CBM inflatable underbalanced safe drilling construction and is of great significance to help increase the single well gas production.