IPTC14866

Trouble Free Drilling with Casing Drilling; a Process Focused on Preventing the Drilling Problems Moji Karimi, SPE, Calvin Holt, SPE,Eric Moellendick, SPE,Tesco Corporation

Copyright 2011, International Petroleum Technology Conference This paper was prepared for presentation at the International Petroleum Technology Conference held in Bangkok, Thailand, 15–17 November 2011. This paper was selected for presentation by an IPTC Programme Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International Petroleum Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the International Petroleum Technology Conference, its officers, or members. Papers presented at IPTC are subject to publication review by Sponsor Society Committees of IPTC. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Petroleum Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, IPTC, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax +1-972-952-9435

Abstract Most drilling problems have been accepted as an inherent part of the drillingprocess. As a result, there has been a great amount of effort put forth to find solutions for said undesirable events after they occur. Much of the industry’scurrent drilling activityis happening in challenging, problematic areas such as depleted sands, HPHTwells, shale gas, deep water, etc. Preventing drilling problems is essential tothe economics of such projects. Casing Drilling has been successfully practicedfor more than a decade, and has proven to be a unique approach in reducing drillingproblems and associated NPT. Some of the most notorious drilling problems are stuck pipe, wellcontrol events, lost circulation, wellbore instability, and drilling induced formationdamage. Since there is no tripping of the drill string during Casing Drilling,thishelps with many of the above mentioned problems. Most importantly, this helps withwell control issues. Also, the small annulus brings about a high annular velocitythat eliminates a lot of cutting transport issues, especially at critical angles. Other benefits of Casing Drilling relate to casing contact with the wellbore walland the well-known, "Plastering Effect". The large diameter ofthe casing ensures that the casing will contact the wellbore wall smoothly and smear the cuttings, filter cake, and the added LCM into the pore spaces. This creates a veryhigh quality, thin, almost impermeable mud cake that isolates the formation. The plasteredfilter cake prevents stuck pipe and lost circulation, improves wellbore stability,and reduces the formation damage caused by filtrate invasion. Casing Drilling has proven to be a reliable option to eliminate drilling problems.It saves time, cost, and the frustration of unplannedevents. It also significantly increasesdrillingperformance andkeepsrigs drilling. Introduction Casing Drilling is a process in which a well is drilled and cased simultaneously. The original purpose of developing Casing Drilling technology was to eliminate Non Productive Time (NPT) associated with tripping and running casing.During early implementation of the technology, other benefits were seen while drilling with large diameter casing as less drilling problems were observed eventhough it was originally thought that drilling with the large pipe would instigate more problems. Years of drilling and exploiting petroleum reservoirs has left the drilling industry with a much more complex environment. Current drilling applications are frequently located in troublesome zones, depleted reservoirs, and wells with severe wellbore instability.Casing Drilling has been used in numerous difficult wells and to drill through troublesome well sections that would not have been possible with conventional drilling techniques. The big question is; what happens when we drill with casing instead of conventional drill pipe. In other words, how can we explain the Casing Drilling benefits in regards to wellbore stability? In this study, the authors try to answer this question in two sections. The first section relates the benefits of Casing Drilling methodologyand inherent differences with conventional drilling. Plastering Effect is introduced and analyzed as a dominant contributor to the unexplained advantages of Casing Drilling.