• Technical Papers

    Below is a list of links to a collection of our technical papers, authored by Quality Tubing or by our partners. Please follow the link to download the full paper from Society of Petroleum Engineers.

    SPE-184806-MS: Development and Compatibility Testing of Coiled Tubing with 140-ksi Specified Minimum Yield Strength  

    This paper presents the recent development of 140-ksi specified minimum yield strength (SMYS) coiled tubing (CT). The introduction provides background on the development. This includes the history of high-strength CT developments and potential new markets. It also defines the testing necessary to verify that the appropriate strength levels are achieved through all welding processes and compatibility with typical CT field equipment.
    The tubing properties verification, steel selection process, and the welding procedure development and testing are discussed. Verification of manufacturability using current CT manufacturing equipment, which includes high-frequency induction welding, is also discussed. Compatibility testing verifies that the tubing can be used with typical CT equipment, such as injectors, blowout preventers (BOPs), and typical connections to pressure pumping equipment.

    The target market for high-strength tubing is high-pressure well intervention and completion operations. Therefore, sour gas compatibility testing should be performed because even modest amounts of hydrogen sulfide (H2S) become severely sour in high-pressure environments. The testing program verifies that while using the available chemical inhibition methods, the tubing/inhibitor system is not susceptible to sulfide stress cracking (SSC), even at extremely sour H2S partial pressures in acidic environments. Finally, testing to verify low-cycle fatigue life caused by exposure with inhibition is discussed based on full-tube fatigue testing, both with and without sour gas exposure.

    The paper concludes with lessons learned during the development process and presents the conclusions regarding the development, applicable markets for use, and any future steps.

    SPE-179080-MS: High-Strength Coiled Tubing can be Used Successfully in Sour Environments if Properly Managed

    High-strength coiled tubing (CT) was subjected to sulfide stress cracking (SSC) testing for the purpose of defining acceptable operating zones in sour environments, both with and without inhibition. In this case, 130 ksi specified minimum yield strength tubing was used. This paper presents a summary of the results with conclusions, lesson learned, and recommendations for sour zones of high-strength CT with and without inhibition.

    Coupons of CT were tested in accordance with NACE TM0177 Method B (four-point bent beams) (NACE TM0177-2005) to determine if cracking occurred in different sour environments. Sour environments were tested ranging from in-situ pH of 2.8 to 5.5 and H2S partial pressure of 0.005 to 10 bar. Testing was performed both including and excluding chemical inhibition. Coupons tested were removed from as-milled tubing and tubing that had been subjected to low-cycle plastic fatigue under pressure on a laboratory CT fatigue testing machine. Plasma arc bias welds, high frequency induction seam welds, and parent material coupons were tested.

    Without inhibition, coupons tested in mild, intermediate, and severe sour environments failed because of sulfide stress cracking. However, when chemical inhibition was mixed into the aqueous environment, coupons tested in severe sour environments produced acceptable results, meaning that no sulfide stress cracking occurred. The acceptable results indicate that, when properly managed, high-strength CT can be used successfully in a manner similar to lower-strength CT when operating in aqueous downhole environments with high sour gas partial pressures. The sour environments tested with and without inhibitor were plotted on a pH versus H2S partial pressure diagram. Based on the failure or no-failure results of the testing, recommended operating zones were then determined and are presented.

    The development of a high-strength CT SSC testing program is also presented in this work. Guidelines for the test program include the preparation of bias weld, seam weld, and parent material specimens and also simulation of the cyclic plastic strain and internal pressure typical of CT operations.

    SPE 179062-MS: Optimization of Coiled Tubing (CT) Performance with the Use of Rapid Tapered Section
    The focus of this work is to optimize coiled tubing string design for greater horizontal reach in unconventional wells using a more rapidly tapered section than historically available. The string design will encompass a single outer diameter with a tapered wall thickness, resulting in a tapered inner diameter.

    Comparison of string properties will include modeling a traditional straight wall (mono-wall) string design compared to a traditional continuous taper (longer tapered sections) and two rapidly tapered sections. The tapering helps limit the weight of the final string, making ground transportation within North America more feasible using common reel sizes.

    Outcomes of the modeling comparing the four string designs will be presented using commercially available software for tubing forces analysis, fatigue modeling and fluid dynamics. This modeling will be used to create a database of theoretical results for typical field applications and parameters with the aim of comparing results to actual field data, when available. At the time this manuscript was authored, production of a string with the preferred design is expected to be possible near the end of 2015.

    By utilizing a tapered design, improved low-cycle fatigue life can be achieved in tapered designs compared to straight wall designs of the minimum wall thickness of the tapered design. The tapered design generally has more desirable mechanical limits compared to the straight wall designs while experiencing limited reduction in friction pressure (due to the tapered inner diameter).

    SPE 143152-MS: New Higher Strength Coiled Tubing Developed to Extend Coiled Tubing Operating Envelopes
    A new high strength coiled tubing grade has been developed to address the demands for improved axial strength, better fatigue performance and the ability to function at higher operating pressures. Coiled tubing service companies and operators defined several areas where existing coiled tubing grades are not considered capable of performing, including carrying heavier payloads to the well perforation zone and working in today's increasingly longer horizontal sections. Designing a coiled tubing product that meets these requirements presented unique challenges. The project goal was to develop reliable high strength coiled tubing that provides 130,000 psi minimum yield strength and predictable fatigue life. Coiled tubing strength comes from a balance of strength from the initial hot rolled strip and modifications while forming into tubing. However, some coiled tubing manufacturing operations, including welding, can influence those strength characteristics. The process controls during manufacturing, including bias welds and any tube to tube welds needed to assemble long strings;  all determine the final properties of the tubing. The high strength tubing has been successfully made using existing manufacturing methods. The initial testing indicates the tubing has high strength with good ductility. Fatigue testing shows superior fatigue performance to existing grades of tubing in both cycles to failure and diametrical growth. This paper will cover the development program inclusive of strip manufacturing, tube forming, welding and other processes including the quality control necessary for assuring consistent properties. Initial application trails to verify operating characteristics will also be reviewed in the paper. 

    SPE 143079-MS: Use of High-Strength Coiled Tubing in High-Pressure/High Temperature Perforating Operations 
    A major operating company (operator) demonstrated interest in the development of high-strength (>125 ksi yield) coiled tubing (HST-CT) for use in high-pressure/high-temperature (HP/HT) fields in the central North Sea. The operator's objective was to perforate underbalanced (in base oil) with coiled tubing (CT) using up to 1,700 ft of guns in one run. The combination of the low hydrostatic pressure of the perforation fluid and high bottomhole-pressure results in high wellhead pressures. Therefore, the CT had to be strong enough to avoid collapsing while pulling the weight of the bottomhole assembly (BHA) and the string inhole from the working depth of a live well. Because of this, the CT needed to be carefully designed to minimize its weight without compromising its strength. Computer simulations were run for string designs made from the currently available materials but none were found suitable for the operator's objective, so the operator pursued the development of HST-CT.

    A major CT manufacturer working in conjunction with a material supplier developed the product and, allied with a service company, proved the product suited the needs defined by the operator.

    It was decided to run the HST-CT in a newly drilled well in the same area but in a shallower reservoir with sub HP/HT conditions as a test bed to determine any potential issues with the use of HST-CT in reverse-deployment perforating operations. This job was performed with a shorter BHA and a lower wellhead pressure than true HP/HT conditions. Some of the operational testing normally conducted in Houston, Texas was performed in Aberdeen, Scotland because of job-time restrictions.

    The test results, operational details of the CT job, and observations and conclusions derived from the use of the HST-CT developed are discussed in this paper.This project involved the first offshore application and the first commercial application of HST-CT worldwide. The importance of this project is highlighted by the increased number of unconventional reservoirs being perforated, thus increasing the need and demand for stronger CT. 

    SPE 154057-MS: Influence of a Straightener on Coiled Tubing Fatigue
    When coiled tubing exits the injector on its way into the wellbore, it contains residual curvature as a result of prior bending events (i.e. being wrapped around the coiled tubing reel). Coiled tubing straighteners are being used increasingly during field operations to remove this residual curvature in order to help delay the onset of coiled tubing lockup and successfully perform work in extended reach wellbores containing long horizontal intervals.

    To straighten the coiled tubing, rollers are used above the injector to apply bending in the reverse direction of the residual curvature. After the tubing exits the straightener assembly, the residual bend of the tubing will have been mitigated and the tubing will spring back into a predominantly straight line. However, the reverse bend applied during the straightening process increases the overall strain range experienced by the tubing and should adversely shorten its fatigue life. Accurate estimation of cumulative fatigue damage along the tubing is critical for making decisions about retiring strings prior to tubing failure, which can result in injury to personnel, equipment damage, unplanned release of fluids at surface, as well as costly fishing operations.

    This paper presents a methodology to quantify the incremental fatigue damage imparted on the tubing as a result of coiled tubing straightener use. An analytical technique is presented to compute the reverse bending radius required for tubing straightening and to quantify its subsequent influence on incremental fatigue experienced by the tubing. The analysis shows that only the radius associated with the tubing reel affects the residual curvature of the tubing under normal field operating conditions. It is also shown that it is not necessary to release the straightener during POOH operations to avoid incremental fatigue damage from straightener use. A case study is presented and fatigue life reduction is estimated on the order of 30% for the example tubing size and grade and the geometry of the deployment hardware. A test program is discussed to explore the influence of these parameters. 

    SPE 153945-MS: Full-Scale Fatigue Testing With 130K Yield Tubing 
    Coiled tubing (CT) is widely used in the well-intervention business as a practical and cost-effective means of servicing wells. Since CT's inception, the use of continuous steel tubular has been the primary means of conduit for the applications required. The performance of CT has vastly improved throughout the years because of advancements in the tubing material and manufacturing processes, as well as extrapolated models predicting low-cycle tubing fatigue life. Because of these developments, CT has expanded to meet the increased demands of deeper and more rigorous wells. Utilization of new higher-strength grades of tubing plays one of the most essential roles for performing in these critical well applications.

    This paper presents results from full-scale fatigue tests performed at several pressures on newly developed 130,000-psi (130K) minimum yield strength tubing. CT made with this new 130K material was cycled to failure in a real-world full-scale fatigue test setup. The collected fatigue-life values will help modify and validate the existing fatigue model used for CT job designs as well as lead to the development of a potential new model with further refinement for critical applications. This full-scale testing also verifies the correlation between tubing life observed in controlled, short-stroke lab-scale fatigue tests and real-world applications. 

    SPE 1780805-MS: Successful Campaign Using Coiled Tubing to Perforate Five HPHT Wells in the UK Central North Sea 
    This paper details the planning, design and execution of a successful campaign to perforate five HPHT wells, using Coiled Tubing (CT), in the UK Central North Sea. The project goal was to perforate extended intervals, in live well conditions, in one run and leaving no guns or restrictions downhole.

    The well conditions presented challenges to the design and operation of CT in this campaign. Challenging factors included:

    • The use of high yield strength CT (130,000ksi grade material).
    • Wellhead pressure up to 9,000 psi.
    • Bottomhole pressure up to 12,500 psi.
    • Estimated BHT 375° F.
    • Estimated FWHT 320° F.
    • Well depths of 21,000 ft MDRKB.
    • Deployment of up to 1,645 ft of 2 7/8” perforating guns.
    • Perforating gun string retrieval to surface.
    • No rathole to drop guns due to:
    • Penetration of the reservoir water bearing zone, potentially leading to produced water and scaling issues in later well life.
    • Access required across the formation for data acquisition and reperforation operations.
    • Cost and time involved drilling hard HPHT formations.

    Job design was critical to the success of the operation and consideration given to learnings from similar previous operation. This included selection and analysis of CT material, size, wall thickness and managing potential CT collapse pressure following reservoir perforation.

    Further analysis, included calculation of CT stretch, circulation pressure, and wellbore solids removal studies.

    Reverse circulation through the CT was carried out. This would increase the effectiveness of fluid displacement when creating an underbalance situation prior to perforation. In order to maintain pressure barriers specific tooling was required to minimize the risk during this operation. 

    Results 1 - 0 of about 0.
    Page 1 of 0  
    Page 1 of 0