TRIP TANK OPERATION

A trip tank is a special mud tank. It is used when they pull drill string from the hole, for example, to change out a dull bit. They also use the trip tank when they run drill string back into the hole. Pulling the drill string and running it back in is called a “trip”, which is why they call the small tank a “trip tank”. They use it to keep accurate track of how much mud the drill string displaces in the hole. Trip Tank Operation When the crew pulls drill string from the hole, the mud level in the hole drops. If they let the mud level drop too far, it won’t exert enough pressure to keep formation fluids from entering the hole. So, as the crew pulls pipe, they continually circulate fluid from the trip tank to replace the drill string and keep the hole full. They also watch for unusual changes, and may make sure that the volume of mud they put in exactly replaces the volume occupied by the drill string. Since the volumes are small, the level of mud in the trip tank is calibrated in small increments, such as stands of pipe, or barrels or liters of mud, or both. If the volume they put in is less than the volume occupied by the drill string they removed, then it’s likely that formation fluids have entered the hole. For example, let’s say the crew pulls one stand of drill pipe. In this instance, the stand displaces .7 barrels or 111 liters. There for, they should pump .7 barrels or 111 liters of mud to replace the stand. The mud level in the trip tank should sure drop .7 barrels or 111 liters. If the level in the tank shows less, then formation fluids have entered the hole and the crew must take steps to control the well.