Casing Drilling vs. Liner Drilling: Critical Analysis of an Operation in the Gulf of Mexico

摘要

Increasingly, operators are looking for simple and effective methods to overcome the hazards and limitations imposed by depleted reservoirs, rubble zones or thief zones. One method is to utilize casing or liner drilling to isolate the problem area by combining drilling and casing in one operation. This can take on many forms from simple drill-in systems to full retrievable directional BHA’s connected below the casing or liner string. A major independent operator has recently drilled two 12-1/4” hole sections in different wells to isolate a problem thief zone (Well A-2 BP01 and A-3). The drilling of one of these sections with liner (A-2 BP01) and the other with casing (A- 3) produced many operational and equipment learning that will increase efficiency in future applications. To drill the problem interval of the A3 well, the operator chose a tried and proven Casing Drive System, together with a new PDC casing bit to drill down a full string of 9-5/8” casing. The choice of drilling with liner or casing is exam ined along with the equipment and operational practices required. Comparisons will be drawn with the offset well which was drilled conventionally and led to mud losses of over 3,000 barrels, the effectiveness of a smear or plastering effect while drilling with liner and casing is investigated.