What is the difference between positive and reverse circulation drilling rigs

Positive circulation and reverse circulation Drilling Rigs have significant differences in the drilling process, mainly reflected in the direction of mud flow and slagging method.

Positive Circulation Drilling Rig

Working Principle:
In a positive circulation drilling rig, mud is pumped from the mud pool by a Mud Pump and transported downward to the drill bit through the inner cavity of the drill pipe.
When drilling, the drill bit crushes the surrounding soil and rock to form drill slag, which rises with the mud along the hole wall and eventually overflows from the hole into the sedimentation tank for sedimentation treatment.
Characteristics:
Weak capacity of slag discharge: as the mud flows upward from below, the slag discharge effect is not as good as reverse circulation in some cases.
Simple process: relatively easy to operate, suitable for sand layer and other geological conditions that are not easy to collapse.
Lower cost: equipment and operation costs are relatively cheap

Reverse circulation drilling rig

Working principle:
Reverse circulation drilling rig, on the other hand, sucks the mud through the outer ring space of the drill pipe, which is sucked in at the bottom of the hole and then rises to the ground through the inner cavity of the drill pipe.
This way makes the drilling slag can be taken away more effectively, thus improving the efficiency of slag discharge.
Features:
Strong capacity of slag removal: as the mud is extracted from the bottom of the hole upwards, it can quickly take away more drilling slag.
Complicated process: the operation is relatively complicated and requires a higher level of technology, applicable to complex geological conditions such as pebbles and clay.
High efficiency: the upward flow rate of the reverse circulation flushing fluid is fast, which usually achieves higher drilling speeds of up to 20 to 30 meters per hour.

Summary

Positive circulation and reverse circulation drilling rigs have their own advantages and disadvantages, and the choice of the right type of drilling rig depends on the specific geological conditions and project requirements. Positive circulation is suitable for simple, stable soil formations, while reverse circulation performs better in complex geological conditions.

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