What Does Critical flow rate Mean?
The critical flow rate can be defined as the maximum production rate or threshold above which the production of sands, along with the production fluid, increases significantly.
Below this threshold, the production of sand along with produced fluid is uniform.
Sand production happens in many oil fields and is common in porous sediments. It is important to control the production of sand to avoid damage to the formation, the collapse of the casing, and damage to surface equipment due to drag forces.
Trenchlesspedia Explains Critical flow rate
In deepwater gas fields, sand production can cause significant damage. Sand production can occur due to events downhole such as formation failure, sand erosion due to flow and sand transport.
The drag forces created by the producing fluid, combined with drawdown pressure effect overcomes the compressive strength of the formation and results in loss of the sand grains.
This suggests that there is a threshold or a critical flow rate, below which a producing well does not allow the compressive strength of the formation to be exceeded by these forces.
Wells can sand up during and after sand production, having varying effects on sand productivity. The productivity seems to increase initially due to the increase of permeability, but after some time the produced sand can obstruct the entrance of hydrocarbon into the well. Sand can also be transported to the surface causing erosion of pipelines, joints, chokes, and valves.