SPE Member Abstract Coiled Tubing is used increasingly to service highly deviated and horizontal wells. A limitation on horizontal displacement occurs because of the frictional forces between the coiled tubing string and borehole while running in coiled tubing. This causes helical buckling and can lead to lockup of the coiled tubing string, thereby limiting reach. This paper will address the various techniques currently in use and propose new techniques to achieve additional reach. The topics that will be discussed are buoyancy reduction, friction reducers, optimal taper and pipe size of coiled tubing, straightening coiled tubing, downhole tractor simulation, flowing fluid, and pumpdown. A tubing forces model has been developed that models these techniques. Results showing additional reach attained will be presented in the form of the surface weight prediction for commercial and conceptual wells. Introduction Extended reach technology (ERT) has allowed the petroleum industry to reach and capitalize on reserves inaccessible to conventional drilling and completion methods. "The application of extended reach technology has resulted in extended field drainage radii, increased production rates, improved reservoir management, a reduction in required platforms and well counts and improved field economics…". Extended reach technology has developed rapidly in the U.K. and Norwegian sectors of the North Sea. Given the type of well profiles, conventional wireline techniques are not appropriate to convey tools and manipulate completion hardware Due to the high angles of the long tangent sections combined with the TVD of the reservoir, such wells are known as extended reach wells. Coiled Tubing is well suited to conduct such operations. The definition of an extended reach well is a well with a measured depth to true vertical depth ratio (MD/TVD) greater than 2.0. A mega-reach well has a MD/TVD ratio greater than 3.0. Furthermore, services conducted with drillpipe or conventional tubing are often performed with coiled tubing to reduce rig costs. The services currently being performed in highly deviated/extended reach wells include perforating, setting and retrieving plugs, opening and closing sliding sleeves, fishing, removing fill, drilling, matrix acidizing and acid washing. A limitation on the horizontal displacement occurs because of the frictional contact forces between the coiled tubing and the wellbore When axial compression forces over a critical value are applied to coiled tubing, the coiled tubing will first buckle into a sinusoidal wave shape. P. 392

As offshore drilling and production continue to move into ever deeper water, supporting the weight of a steel riser becomes a major design issue. For dry tree systems, the problem is further exacerbated when high pressure reservoirs are encountered and heavier thick-wall risers are needed. One solution with significant potential is steel pipe over-wrapped with composite material, combining a durable and fluid tight bore with the exceptional strength and reduced weight of carbon fiber reinforced epoxy. This paper summarizes work performed under RPSEA project 07121–1401 to design a lightweight riser joint as part of a surface BOP drilling system, for a water depth of 3 048 m (10,000 ft) and having a 103,4 MPa (15 kpsi) pressure rating. Introduction Surface BOP (SBOP) systems in deepwater have been a novel way to significantly reduce the amount of time and CAPEX associated with drilling a well. Many operators believe this technology is the model for cost-effective field development in ultra-deepwater. However, at increased depths, supporting the additional weight of the riser and its associated equipment becomes a driving factor, and its impact on the floating platform can be limiting, if not prohibitive. This is particularly true when high pressure thick-wall risers are needed. Design of the riser also has its constraints; increasing material strength increases the risk for metallurgical failure as high-strength steels are more susceptible to embrittlement and stress cracking, and increasing wall thickness increases weight and fabrication may not be feasible. This paper summarizes work performed under RPSEA project 07121–1401 to design a lightweight composite-reinforced steel riser joint as part of a surface BOP drilling system for ultra-deepwater high pressure wells. The design basis is a single barrier riser for a tension-leg platform (TLP) or spar in 3 048 m (10,000 ft) of water and having a 103,4 MPa (15 kpsi) pressure rating. Project funding was provided through the NETL/RPSEA ultra-deepwater program. The project started in January 2009 and was completed in September 2011. The RPSEA design is in essence a conventional full-bore steel drilling riser joint with the tube body section over-wrapped with composite material. Like a conventional riser joint, the steel member is an assembly of two end couplers welded to each end of straight pipe. End couplers, in addition to the flange, include a thick-wall section for handling the joint and engaging with the spider, followed by a series of tapered grooves related to the traplock metal-to-composite interface (MCI), a feature at both ends of the joint to incorporate the composite and steel members. The steel assembly is over-wrapped by filament winding. Successive layers of continuous carbon fiber roving wetted with epoxy are wound, creating a multi-layered angle-plied laminate. Composite thickness and laminate architecture are determined based on required hoop and axial strengths. An illustration of the RPSEA design is presented in Figure 1.

Recently, the Modal Decomposition and Reconstruction (MDR) algorithm was developed to accurately estimate fatigue damage in marine risers based on measured acceleration and angular rates at several locations. The greatest benefit for drilling risers can be derived by incorporating the method in an online, fully automated system. In this way, fatigue damage estimates are available to the crew on the rig in real-time for risk quantification and mitigation. To this end, the MDR routine was implemented for online assessment of fatigue damage along the entire riser from acceleration and angular rate measurements at typically 5–10 elevations. This paper discusses the architecture, highlights some measured data and provides results for modes, stress and fatigue damage rate for the Chikyu drilling vessel during two scientific drilling campaigns. These campaigns occurred at the Shimokita site (1180-meter water depth) and the Nankai trough site (1939-meter water depth). To the authors’ knowledge, real-time fatigue monitoring of the entire riser has not been accomplished previously. Robust incorporation of the MDR algorithm into an online computational environment is detailed, including incorporation of top tension and mud weight data from the rig, detection and removal of data errors, and streamlined flow of the data through the computational modules. Subsequently, it is shown by example how the measured accelerations and angular rates are used to determine excited modes, participating modes, stress distribution and fatigue damage along the entire Chikyu drilling riser in an online setting. The technology highlighted advances riser integrity management two steps forward by first using measured data at 5–10 locations and the MDR algorithm to reconstruct stress and fatigue damage along the entire riser, and secondly integrating this approach into a fully automated, real-time computational environment. As a result, drilling engineers are empowered with a tool that provides real-time data on the integrity of the drilling riser, enabling informed decisions to be made in adverse current or wave conditions. Measured data also serves as a benchmark for analytical model calibration activities, reducing conservatism in stress and fatigue in future deployments. Furthermore, cumulative fatigue damage can be tracked in each riser joint, enabling more effective joint rotation and inspection programs.

Extended reach technology (ERT) has allowed the petroleum industry to reach and capitalize on reserves inaccessible to conventional drilling and completion methods. ERT has developed rapidly in the UK and Norwegian sectors of the North Sea. Given the type of well profiles, conventional wireline techniques are not appropriate to convey tools and manipulate completion hardware. Coiled tubing (CT) is well suited to conduct such operations. A limitation on the horizontal displacement occurs because of the frictional forces between the CT string and borehole while running in CT. This causes helical buckling and can lead to lockup of the CT, thereby limiting reach. When coiled tubing is wound off a reel and bent over the gooseneck and then passed through the injector into the well, the coiled tubing undergoes plastic deformation and is subjected to residual bend. The residual bend imposes contact forces between the CT and the wellbore. A CT straightener was developed to remove residual bend and improve extended reach. A description of the CT straightener experiments and trials will be outlined. Additionally, the various techniques currently in use will be addressed briefly. Introduction "The application of extended reach technology has resulted in extended field drainage radii, increased production rates, improved reservoir management, a reduction in required platforms and well counts and improved field economics…". ERT has developed rapidly in the U.K., Norwegian and Danish sectors of the North Sea. Given the type of well profiles, conventional wire line techniques are not appropriate to convey tools and manipulate completion hardware. Due to the high angles of the long tangent sections combined with the TVD of the reservoir, such wells are known as extended reach wells. Coiled Tubing is well suited to conduct such operations. The definition of an extended reach well is a well with a measured depth to true vertical depth ratio (MD/TVD) greater than 2.0. A mega-reach well has a MD/TVD ratio greater than 3.0.

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