Distinction between tubing and casing？

Tubing is the pipe that passes into the casing of an oil well during normal production. In a nozzle well, oil flows through tubing to the surface and into the collection and transport process. In a mechanical production well, the tubing, rod, and deep well pump (the "triple pump" unit) are combined to bring the oil pump to the surface for collection and transport.

The casing is the pipe that goes into the well after drilling. The casing and the wall of the well are sealed with cement, and then the target layer is perforated with a perforating gun to allow the oil to flow through the rock layer, the cement ring, and then the casing is inserted into the bottom hole, and the tubing is inserted into the surface.

The main functions are:

1. Reinforce the borehole wall to prevent formation collapse;

2. Separate different oil and water layers to achieve stratified production;

3. Facilitate the implementation and maintenance of fracturing, acidification, etc.

4. Form oil flow channel and cooperate with tubing to achieve the purpose of oil return.

The sequence is as follows: after laying the well, the casing starts to run, the casing and the well wall are sealed with cement, and the tubing is extended into the casing. Downhole tools, such as oil packers and pumps, are attached to the pipe, and the rod is inserted into the tubing. The rod pulls the piston of the pump.