Both the liquid-gas separator and the vacuum degasser are degassing devices used in drilling fluid solid control systems, but they differ significantly in their working principles and applications. The liquid-gas separator is primarily designed to remove large gas bubbles from drilling fluid, while the vacuum degasser targets smaller gas bubbles. The liquid-gas separator operates using physical principles for gas-liquid separation, whereas the vacuum degasser relies on a motor and vacuum pump. Below is a detailed comparison of their differences.
1. Different Applications of Liquid-Gas Separator and Vacuum Degasser
- Liquid-Gas Separator: This device is used to remove large gas bubbles from drilling fluid, typically those with diameters ranging from 3 to 25 mm. These large bubbles, often expansive gases filling sections of the wellbore annulus, can cause well kicks or even blowouts at the rotary table surface. The liquid-gas separator can receive fluid directly from the rotary blowout preventer or the choke manifold to separate these large bubbles. After processing, the drilling fluid, which may still contain smaller bubbles, passes through a shale shaker and then enters the vacuum degasser for further degassing.
- Vacuum Degasser: This equipment is designed to remove small gas bubbles from drilling fluid, not the large bubbles expelled from the wellbore annulus. Its primary function is to restore the drilling fluid’s density, stabilize its properties, and improve its quality.
2. Different Operating Principles of Liquid-Gas Separator and Vacuum Degasser
- Liquid-Gas Separator: The liquid-gas separator relies on physical principles for separation and requires no external power source. When gas-entrained drilling fluid enters the separator, it first strikes a wear-resistant steel baffle, which reduces the fluid’s flow velocity and protects the separator body from wear. The fluid then flows downward over a series of specially designed internal baffles, creating a turbulent state that facilitates gas-liquid separation. The free gas is discharged through the gas outlet at the top of the tank, while the drilling fluid is directed to the circulation tank.
- Vacuum Degasser: The vacuum degasser requires powered equipment, such as a motor and vacuum pump, to separate gas from drilling fluid. It uses the suction of the vacuum pump to create a negative pressure zone inside the vacuum tank. Under atmospheric pressure, the drilling fluid enters the hollow shaft of the rotor through an inlet pipe and is then sprayed outward through windows around the shaft, hitting the tank wall. This collision, combined with the action of a separation wheel, causes the drilling fluid to form a thin layer, allowing gas bubbles immersed in the fluid to break and escape. The separated gas is discharged through the exhaust pipe of a gas-water separator to a safe area, while the drilling fluid is expelled from the tank by an impeller. The main motor starts first, driving the impeller to rotate at high speed, ensuring that drilling fluid enters the tank only through the inlet pipe and is not sucked in through the discharge pipe.
Summary
In summary, the liquid-gas separator and vacuum degasser serve distinct roles in drilling fluid solid control systems. The liquid-gas separator uses physical principles to remove large gas bubbles without requiring power, while the vacuum degasser employs a motor and vacuum pump to eliminate smaller gas bubbles, enhancing drilling fluid quality. Understanding these differences can help optimize their use in drilling operations.