CPD, also known as shell and auger drilling, uses a large tripod rig and winch to lift and drop a cutting tool inside a steel casing tube. This case maintains stability and prevents the borehole collapsing from any insecure soil. The cutting tool used is dependent on the type of ground substrate.
[pdf] One of the most significant advancements to reduce costs for drilling multiple horizontal wells from a single surface location or pad is the “walking” rig. A walking rig is self-propelled because it can move short distances (10 metres) without being disassembled and with pipe in the derrick.
[pdf] One of the most significant advancements to reduce costs for drilling multiple horizontal wells from a single surface location or pad is the “walking” rig. A walking rig is self-propelled because it can move short distances (10 metres) without being disassembled and with pipe in the derrick.
[pdf] 
