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QT-16Cr coiled tubing was introduced as a commercial product in the spring of 2004. This high strength corrosion resistant alloy product was developed to offer a cost effective coiled tubing solution for both injection and secondary production applications in wet CO2 environments where carbon steel products may not be suitable. This paper focuses on the results of two years of field applications and laboratory testing with the intent of defining the suitability and limitations of QT-16Cr as a completion string subjected to varying concentrations of CO2, H2S, chlorides and pH. The combination of actual fluid and gas analysis from wells where QT-16Cr has been employed will be compared to autoclave testing which simulates downhole conditions with applied stress on the tubing. This paper also addresses the manner in which QT-16Cr has a positive effect on production system economics using several S. Texas wells as examples. A review of field tests utilizing QT-16Cr as work strings will be covered. Attributes will be reviewed inclusive of abrasion characteristics when run inside 13 chrome production tubulars and low cycle fatigue performance data. Both operators and service providers that have potential applications for corrosion resistant alloy coiled tubing should have interest in this update and overview regarding the performance of QT-16Cr coiled tubing. Developing The Case (QT-16Cr) For many years specific requirements for corrosion resistant coiled tubing have been requested with manufacturers making efforts to produce tubing from exotic materials such as Titanium, Nickel alloy 625 and Beryllium Copper. Although these efforts were valiant, the material and manufacturing limitations coupled with lack of supporting system economics led to their early demise. In early 2000 it was clear that niche applications requiring exotic alloys with fluctuating commodity pricing would not sustain coiled tubing manufacturing efforts. At this time many gas producers were embracing the advantage that coiled tubing had to offer as "velocity" or "siphon" strings for reestablishing the productivity of gas wells. With the system economics favorable for velocity applications, many operators began multiple well coiled tubing completions creating a substantial demand on coiled tubing manufacturers. It was apparent that many of the aging gas wells were developing environments non-suitable for the relatively thin walled carbon steel coiled tubing. The primary Achilles heel being the age-old problem; the encroachment of water along with partial pressures of CO2, resulting in carbonic acid. This increased demand was the driver for the development of QT-16Cr. The need for a CRA coiled tubing became apparent when many older gas wells producing CO2, commonly referred as sweet corrosion, combined with direct water production and/or the introduction of condensed water created as the gas traveling to the surface passes through its critical condensation temperature corroded standard coiled tubing stings. These conditions generate carbonic acid which can create extremely corrosive environments for carbon steel coiled tubing as depicted in figure 1.

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fax 01-972-952-9435. AbstractSixteen chrome coiled tubing (16Cr CT) was introduced in the spring of 2003 and over 200 strings have been put into field use as velocity strings. Following preliminary testing, two 16Cr CT reels were deployed at Prudhoe Bay, Alaska to evaluate feasibility as an intervention workstring. The two reels performed a variety of standard CT applications on a daily basis. Observations and data were gathered to determine operating guidelines, applicability, and limitations. The field trial indicated that 16Cr CT can be deployed in the field with only minor operational modifications.16Cr has superior abrasion resistance in 13Cr production tubulars and little CT surface (external) wear was seen during the field trial. The second reel developed a pinhole failure earlier than expected; however, analysis of the adjacent material indicates that 16Cr has increased low cycle fatigue life when compared to standard carbon steel CT. Additional testing is ongoing, and it is felt that the conditions resulting in the failure can be mitigated to avoid future premature failure. This paper documents the lab and field trial results. Standard operating procedures for 16Cr CT are described that provide easily implemented guidelines. 16Cr has applicability as an intervention workstring, particularly in corrosive environments and in areas where abrasive 13Cr production tubulars must be endured.Recognition is extended to the BP Alaska Wells Team who contributed to making the 16Cr CT field trial a success. Special recognition is made to