The choke manifold has the following main functions:
It controls wellhead pressure and improves safety.
It maintains a certain flow rate based on the requirements of the test. Testing requires different flow rates over multiple times, requiring the use of different choke sizes.
Prevent formation sand from entering the well by restricting the flow rate. Restricting the flow rate reduces the velocity of the fluid, thus minimizing the amount of sand entering the well.
It also prevents condensation of water and gas by restricting flow.
It is also used to ensure that flow is critical, which means that pressure fluctuations downstream of the choke manifold do not affect the well's downhole pressure and flow rate.