What Is a Jet Bridge?

Sand bridge refers to the bridge plug formed when the diameter of the wellbore is irregular, the drilling fluid often generates eddy current at the enlarged diameter and sinks the cuttings carried by it, and focuses at the lower diameter.

1. It is very easy to occur when drilling with soft water in soft formations, because soft formations have fast mechanical drilling speed and many cuttings, while the suspension capacity of clean water is poor and rock cuttings sink quickly. Especially when drilling with a scraper bit, the particle size of the drill cuttings formed is large, such as big eggs and small ones such as walnuts. Once the cycle time is stopped for a long time, it is easy to form sand bridges.

2. The surface casing is too little and soft

1. When drilling, the wellhead does not return drilling fluid, or the fluid is sprayed back in the drill pipe. After the bit enters the sand bridge, the drilling fluid discharged by the drilled concrete cannot be returned from the wellhead because the sand bridge interrupts the circulation path, and it is forced to enter the bit to return from the drill pipe or squeeze into the soft formation.

2.Before the sand bridge is not fully formed, there may be no resistance or low resistance when drilling down, and the resistance gradually increases as the drilling tool continues to deepen, so the resistance of the drilling tool is soft and no resistance. Hair resistance point. Occasionally the drilling tool does not increase in suspended weight because the increased weight of the drilling tool is offset by the resistance of the sand bridge.

3. If a sand bridge occurs during drilling, the liquid level in the annulus will not drop, and the liquid level in the water hole of the drilling tool will drop very quickly.

4. After the drilling tool enters the sand bridge, it can move up and down freely before the pump is turned on. If the pump is to be circulated, the pump pressure will rise, the suspended weight will drop, and the wellhead will not return drilling fluid or return very little.

5.During drilling, if the drilling fluid displacement is small or the sand carrying capacity is not good, there is no resistance to the up and down movement of the drilling tool during the pumping cycle. Once the pump is stopped, the drilling tool cannot be lifted, especially without solid Phase drilling fluid, this happens more often.

6. During gas drilling, we found that there are water and mud in the returned cuttings, the pump pressure rises, and the amount of returned gas is reduced or not returned. There is resistance in lifting. ^[1]