CasingDrillingMakingMajorStrides.docVIP

Casing Drilling Making Major Strides PAGE 1 PAGE 5 Casing Drilling Making Major Strides By Mike Wardley ABERDEEN, SCOTLAND–Key advancements made over the last few years in the supporting component pieces have resulted in major strides for drilling with casing technology in general, enabling the practice of drilling with casing to move from a niche application to a more widely used technique that can have a significant effect on drilling economics. As the name implies, drilling with casing technology uses a casing string as a direct drill string, instead of conventional drill pipe. This concept was born in the 1950s when it was common in some areas of the world to drill-in the final tubing string, and cement it in place along with the drill bit. To the majority of engineers, the concept of drilling with casing evokes an image of a technology that has been struggling to break through technological and operational barriers for years. Indeed, it is true that until very recently, drilling with casing operations could accurately be described as existing “out of the mainstream” of drilling operations. Yet, drilling with casing does have a successful history and modern techniques have been developed and described extensively in industry literature. Beginning in the early 1990s, sections into depleted reservoirs were drilled with liners in areas where conventional drilling techniques had been proven ineffective. Initially, these were drilled using one of two approaches. In the first approach, a hydraulic motor and bit assembly were latched into the lower-most casing joint and the casing was advanced behind the drill bit by pumping through the motor, in much the same way that “slide” drilling is accomplished using drill pipe. When total depth was reached, the bit and motor assembly were retrieved from the latch mechanism using a retrieval tool run inside the casing. A float valve assembly was then run in its place, followed by cementing operations. The second approac