The DTH drilling rig (down-the-hole drilling machine) is a kind of drilling machine, which is mainly used for drilling in rock formations. The down-the-hole drilling rig uses the impactor and the DTH drill bit.
[pdf] Mars field was discovered in 1989 at around 130 miles south of New Orleans. The field, located at 3,000ft water deep, started production in 1996. Mars B was discovered after Shell geologists located untappe.
[pdf] Kulluk was an ice-strengthened that was used for oil exploration in the Arctic waters. She was constructed by in in 1983 and operated in the Canadian Arctic until 1993 when she was mothballed for over a decade. In 2005, she was purchased and extensively refurbished by Shell PLC for drilling off the .
[pdf] 
