Question

What is main difference between direct circulation drilling and reverse circulation drilling?

Answer

In straight circulation drilling and reverse circulation drilling, major difference in drilling system is related to direction of movement of drilling fluid. In direct circulation drilling, drilling fluid is circulated from drill stem and then flows up the annulus between outside of drill stem and borehole wall. Drilling fluid that carries drill cuttings flows to surface and subsequent settlement pits. Pumps are working to lift cuttings free fluid back to drill stem.