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Deepwater fields are one of the largest growth segments of the industry. The technologies that enable this growth economically are those that provide improvements in operational reliability, flexibility, and cost, and which mitigated risks. With offshore rig rates often hitting $500K US per day, special considerations must be taken into account when specifying or designing an upper deepwater completion at depths greater than 1,000 ft (305 m). When selecting a completion scenario, an accurate assessment of risk versus reward must be analyzed in order to design a cost-effective, yet flexible completion. In this paper, the authors outline the proper methodologies in selecting existing technology for each completion approach in subsea and dry tree applications.
Design methodologies for deepwater completions vary when compared to conventional type completions. The basis of design in a conventional type completion includes: 1) a production packer to isolate pressure and fluids from the producing zone and manage production tubing movement and loads; 2) a surface-controlled subsurface safety valve (SCSSV), whose objective is to isolate the tubing and well head from well fluids in an emergency or planned shutdown; and 3) flow control equipment, such as landing nipples, chemical injection nipples, and sliding sleeves. Deepwater subsea or dry tree completions have similar basic requirements as that of conventional completions. However, critical to deepwater are the completion design, planning, quality assurance and quality control, reliability, execution/deployment, and longevity of the completion.
Drivers for completion methodologies in subsea and dry tree applications will be discussed. Issues such as tubing space-out, packer-setting methods, SCSSV operating parameters, sub-mudline tubing and packoff hangers will be reviewed. Temporary well suspension methods will also be discussed where applicable and different completion options will be outlined for each case.