In the process of gas test in sand production well, the pressure difference of
desander often rises rapidly, so it is impossible to change the sand cylinder or clean the filter screen in time, which results in the deformation
and damage of the filter screen and the interruption of gas test. A warning device for desander sand discharge is developed according to the
structure and working characteristics of the screen type desander, which is composed of four parts: pressure and differential pressure sensor, PLC
controller, alarm and electric valve. The pressure difference sensor monitors the pressure difference of the sand filtering cylinder through
the upstream and downstream pressure sensors. When the pressure difference approaches the maximum allowable working pressure difference, the PLC
controller will command the warning system to give an alarm. When the pressure difference continues to raise to the dangerous value, the PLC
controller will command the electric valve to open quickly to discharge sand so as to reduce the pressure difference of the working cylinder and
protect the filter screen. For Well ZS32, an opening differential pressure is set as 21 MPa and a replacement differential pressure as 30 MPa.
When the pressure difference reaches 21 MPa, the electric valve will be fully opened within 10 s, and the alarm will give an alarm. When the
pressure difference reaches 30 MPa, the alarm will automatically convert the sand barrel, and the alarm will be normal. The device can improve
the adaptability and safety of the filter screen desander and ensure the smooth of gas test construction under the extreme operating conditions of
low temperature, high pressure and high sand discharge.