takeover, page-31

1. A CT unit could not drill a complete hole from surface efficiently or cost effectively : it is designed to primarily perform specific drilling activities when the main surface hole has already drilled.
2. One advantage of using a CT unit for drilling lies in its ability to drill through reservoir without needing a heavy mud column in the well bore ... ie underbalanced... the reservoir pressure may exceed the hydrostatic pressure in the well bore... thus alleviating one key mechanism of formation damage, and wellbore control difficulties such as experienced in SB1.