The Challenge for the Coiled-Tubing Industry
- C.G. Blount (Arco Alaska Inc.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- May 1994
- Document Type
- Journal Paper
- 427 - 430
- 1994. Society of Petroleum Engineers
- 1.8 Formation Damage, 1.7.5 Well Control, 1.6 Drilling Operations, 1.7.1 Underbalanced Drilling, 1.10 Drilling Equipment, 3.1.2 Electric Submersible Pumps, 1.14 Casing and Cementing, 3.1.6 Gas Lift, 3 Production and Well Operations, 2 Well Completion, 4.2.3 Materials and Corrosion, 4.2 Pipelines, Flowlines and Risers, 2.4.3 Sand/Solids Control, 4.1.2 Separation and Treating
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Technology Today Series
From Aug. 9 through 14, 1992, approximately 80 individuals from throughoutthe globe met in a seemingly remote area of the Colorado Rocky Mountains withone common bond: advancement of coiled-tubing (CT) technology. This was thefirst SPE Forum Series meeting devoted entirely to CT technology. After longdays of sometimes heated debates, the final session found these individualscharged with the task of identifying areas where CT industry developmentefforts need to be focused "to utilize the untapped potential ofCT."
Numerous ideas and opinions were generated at the SPE Forum Series meetingto create a long list of areas with high leveraging potential (high return oninvestment) for an oil industry well below the crest of a "boom" cycle.However, from the master list, each individual was given the opportunity tovote for only three issues that they felt were the most pressing. The 17 itemsthat survived the exercise are listed below, "prioritized" by thisgroup's vote.
1. CT drilling technology
2. Standardized CT fatigue testing and computer model
3. Material, equipment, safety, and maintenance standards
4. Well-control equipment
5. CT completion and production equipment
6. CT material advancements
7. CT cleanout technology
8. Special application CT tools and equipment
9. High-pressure abrasive jet technology
10. Hybrid CT units (special purpose; i.e., CT on rigs)
11. Equipment for operating with and in higher pressures
12. Improved information exchange
13. Job planning and operational guidelines
14. Larger-diameter CT (and peripheral equipment)
15. Simplified hydraulics
16. Floating operations CT technology
17. Electronic monitoring and control of CT units.
A year and a half later, where do these leveraging ideas fit into theoverall CT industry picture?
CT Drilling, High-Pressure Abrasive Jet Technology, and Hybrid CT Units
Interest in CT drilling is high from a technology standpoint. However,real-world economics of CT drilling are not attractive in many areas. Drillingusing a CT unit requires a relatively large investment in specialized equipmentto perform the work and the latest in technology to meet the challenge ofapplying the techniques within the inherent constraints of CT, such as no piperotation, limited pressure cycles, and lower flow rates.
A recent paper devoted to CT drilling reports that 39 wells were drilled orre-entered with CT in the last 3 years follow ing pioneering work in Canadaduring the mid-1970's. Information from Canada reveals a considerably highernumber of short-distance, well-deepening CT operations, many of which wereunderbalanced, and a few wells drilling from surface. Total CT drilled ordeepened wells over the last 2-1/2 years is about 200. The latest in CTtechnology and equipment is competing with decades-old, conventional rotarytechnology, which requires very few new techniques and has an untold number offully depreciated rigs available to perform the task. Considering these facts,it is understandable why the economics of the comparison look less thanoptimal. So why bother?
Fortunately for the CT industry, there are niche markets and a fewtechnological advantages to CT that can make the effort to develop thetechnology worthwhile. Re-entry work is one natural target for CT units thatprovides a relatively large potential market. And one often-cited advantage toCT is the smaller footprint and greater mobility of the equipment relative tocommon rotary rigs. CT advantages, however, come with a significant reductionin operational flexibility that demands the new techniques and tools previouslymentioned.
Another potential advantage to CT drilling is the prospect of underbalanceddrilling, which is required in very-low-pressure reservoirs and for formationdamage mediation. The search for a nondamaging drilling and completiontechnique is heightening interest in underbalanced drilling in many areas.Recent efforts in Canada and on Alaska's North Slope034,504 focus CT drillingefforts toward this goal with some encouraging results. In a recently completedNorth Slope well, penetration rates of 100 ft/hr and initial production rates300% higher than anticipated were realized when actual under balancedconditions were achieved during portions of the CT drilling process. Theunderbalanced conditions were achieved using gas lift in the existing 4 1/2-in.production string. Interestingly, previous attempts in Alaska at achievingunderbalanced conditions during drilling were unsuccessful, partly because of aconservative gas-lift design coupled with inaccurate tubing-hydraulics modelpredictions.
Shallow-length CT deepening operations are cost-competitive with aconventional rig in most areas.
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