This paper describes both the challenges and development of a novel solution involving 3.5-in. diameter coiled tubing (CT) for deepwater pipeline commissioning applications. The work scope required that the complete solution be capable of multiple deployments and recovery operations using a single string of 3.5-in. CT from a floating support vessel. The project began with a detailed analysis of the existing available equipment and tools to determine their suitability and limitations for this application. Factors in this analysis included the limited vessel space available for surface equipment, crane capacity, and the suitability of equipment for working outboard on a vessel. This led to the planning, designing, and sourcing of suitable CT equipment. Trials were performed onshore to optimize the rigup, stackup, vessel layout, and assemblies handling. The combination of pre-operation planning and trials led to confidence in the new tools, work methods, and risk assessments. Because the purpose of the deployment work was to complete the commissioning work on several different marine pipelines and risers, the equipment and work methods had to be easily transferred between vessels. This paper presents and discusses the range of technologies that were developed and successfully applied for the first time globally to complete the project. These include the first fully sealable subsea quick-disconnect for CT, the first pump-through modular clump weight, and the first real-time, high-cycle fatigue (HCF) monitoring system to aid in CT pipe management. The deployment and recovery operations involved a wide range of challenges and led to the development of specific tools and methods for using large-diameter CT equipment. In addition to discussing the design and development of the solution, this paper presents the results and lessons learned from successfully using the large-diameter CT downline solution for deepwater pipeline commissioning applications.
This paper describes the challenges involved with providing a coiled-tubing (CT) intervention solution from the helideck of a normally unmanned installation (NUI) in the Gulf of Cambay in offshore India.
The project began with a detailed analysis to determine if intervention was practical from the helideck of the NUI, or if barge support or a full jackup-rig intervention was necessary. Some factors in this analysis included the limited deck space, restricted crane capacity, and the existing available utilities. This led to the planning and sourcing of suitable CT, flowback equipment, nitrogen, and fluid-pumping equipment, as well as necessary downhole tools. Trials were performed onshore to optimize the rigup, stackup, and deck layout. The boat loading and lifting plans were created from these trials. The combination of the prejob planning and the trials led to the confidence to conduct this intervention with modified safety arrangements required for the platform when no helicopter operations could be performed.
The purpose of the actual intervention was to complete sand cleanout of the horizontal-well section, isolate the lower oil-producing zone, open a sliding sleeve to access the upper zone, and unload the well with nitrogen to restore production.
This paper also includes the variety of applied technologies that were either attempted or successfully used to bring the well back into production. This required the use of the latest generation of horizontal, downhole-tool solutions, slickline tractors, CT-tool deployment, and contingency operations, which involved a wide range of downhole tools. The results from the intervention and the lessons learned are presented.
A number of small NUIs exist in the Gulf of Cambay on the west coast of India. The installation discussed in this work had only limited utilities available. These typically include lighting, electrical power (220 volt, 50 Hz, 16 amp), and telephone communications. Neither compressed nor instrument air were available. The installation cranes were limited to a maximum lift of 3 tons. During well workovers, the installation helideck was not available for landings. The well subject to this intervention is only accessible from the helideck. The well was highly deviated with the trajectory beyond 2000 m, ranging from 70 to 80°. The production interval consisted of two top gas zones and two oil zones and was put on production in January of 2008. The upper gas zone and lower oil zones were put on comingled production (Figs. 1 and 2). Sanding and water problems were observed in the well within six months of it coming on production. The source of the water and sand was not fully confirmed. The well had been kept shut since July of 2008. Approximately one year later, the oil-producing zones were put on production but did not flow because of water loading. Sand was removed from the well using bailers run on E-line, and a sliding-sleeve door (SSD) shifting tool conveyed by tractor was used to close off production from the top gas zone. Approximately one hundred E-line tractor runs were performed for cleanout. During cleanout, sand bridges were observed. The depth limitation of the E-line tractor was 2146 m measured depth below rotary table (MDRT). Current reservoir pressure was 1,630 psi at 1233 m true vertical depth below rotary table (TVDRT), and the reservoir temperature was 185°F at 1303 m true vertical depth (TVD).
CT intervention was required for cleaning out the sand to the depth of 2700 m. There were several potential options considered for CT intervention, including the use of a supply a barge, a rig, or performing the job from the helideck. An evaluative comparison was performed between these options with the goal of identifying the smallest equipment setup for performing a CT sand-cleanout job and subsequent plug installation employed by performing a SSD open operation and final nitrogen lift operation on the helideck of a NUI in the Gulf of Cambay with limited deck space, deck load, crane capacity, and height. As part of this evaluation, several previous not dissimilar operations were examined and discussed (Barclay et al. 2006).
Copyright 2006, Society of Petroleum Engineers This paper was prepared for presentation at the 2006 SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition held in The Woodlands, TX, U.S.A., 4-5 April 2006. This paper was selected for presentation by an SPE Program Committee following review of information contained in a proposal submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied.