Drilling sand bridge stuck and accident treatment

Sand bridge stuck is also called sand settling stuck, its nature is similar to collapse, and its harm is worse than sticking stuck.

1.The reason of sand bridge formation

(1) It is easy to occur when drilling with clean water in soft formation;
(2)The surface casing is too little, and the soft stratum is exposed too much;
(3) Adding excessive flocculant to drilling fluid;
(4)mechanical drilling speed is fast, drilling fluid displacement can not keep up;
(5)Change the original drilling fluid system in the well, or drastically change the performance of the drilling fluid;

Sand bridge sticking phenomenon

(1) No drilling fluid is returned to the wellhead during drilling or the drilling fluid is reversed in the drill pipe;

(2) The resistance of drilling tools is soft resistance, and there is no fixed sudden resistance point;

(3) If sand bridge occurs during drilling, the annulus liquid level drops, and the liquid level in the water hole of the drilling tool drops quickly;

(4) After the drilling tool enters the sand bridge, before the pump is started, the up and down movement and rotation are free. If the pump is to be started, the pump pressure will rise, the suspended weight will drop, and the drilling fluid will not return or return very little at the wellhead;

(5)In drilling, such as small drilling fluid displacement or poor sand carrying capacity, in the pump circulation process, the drilling tool up and down movement rotation is no resistance, once the pump is stopped, the drilling tool can not be lifted, especially no solid phase drilling fluid, this happens more.

Prevention of stuck sand bridge

(1) It is best not to drill with water;

(2)In the open hole section, the time of drilling fluid resting should not be too long;

(3) Optimization of drilling fluid design;

(4) When drilling, the appropriate amount of pump should be selected according to the formation characteristics;

(5) To maintain the stability of drilling fluid system and performance.

Treatment of stuck sand bridge

(1) If the drilling fluid can only enter the pump, the drilling tool is stuck, and it can not be moved, it should be calculated the position of the card point, and the time should be reversed from the near the card point.

(2) The position of sand bridge formation may be in the upper part or the lower part, but its well section is not too long, and it is impossible to bury all the drilling tools. If the sand bridge is in the upper part, although there are not many drill tools poured out for the first time, it is impossible to use a long barrel sleeve milling to remove the sand bridge, and then the drill tool is on the button to restore the circulation, and the laterthings are easier to do. If the sand bridge is in the lower part, the method of blasting loose backbuckle should be used to pour the unstuck drill tool at a time, and the following drill tool can only be unstuck by milling backbuckle.

(3) Sand bridge stuck drilling often occurs in the process of tripping, the drill is not at the bottom of the hole, so in the milling process, the fish may sink, in this case, it should be immediately on the button, the drilling tool, it is possible to release the card in the activity. If we can also circulate the drilling fluid, all problems will be solved.

(4)If the drill string is equipped with a centralizer, the sand bridge is often above the last centralizer, so after the casing mill to the centralizer, it is not necessary to reamer to mill the centralizer, and the jar can be jolted and unstuck.