New Subsurface Safety Valve Designs Or Slimhole / Monobore Completions
Authors: Vinzant Mike , Smith Roddie 
Published: June 2014

Over the past decade, operators have been faced with an ever-increasing demand to reduce operational costs. One approach to effecting this reduction has been to maximize production tubing bores while reducing corresponding casing sizes. These new concepts have required many completion configurations and related equipment to undergo extensive change. An excellent example of how new requirements for design enhancement for one technology can impact the design of related equipment is shown in a review of the slimhole / monobore completion technique. This paper wiii discuss enhancements to subsurface safety valve equipment that have been required by the need to support the new requirements of siimhole monobore technology.

The paper wiii present an overview of:The evolution of the flappers designThe constraints various flapper designs place on OD / ID ratios of the safety valve for slimhole monobore completions.The extensive testing that has been performed to verify performance capability.

Comparison of OD/ID capabilities will be made between conventional "fiat plate" flappers, curved flappers, and bail vaive designs. Finaliy, the design of a proven flapper that uses a uniquely contoured configuration to 1) optimize OD / ID ratio, 2) provide enhanced metal-to-metal sealing capabilities, and 3)address the problems faced with other safety valve design options will be presented.

INTRODUTION

In designing a particular safety valve, the outside diameter (OD) or inside diameter (iD) is usually determined by the closure mechanism. Closure mechanisms typically used for subsurface safety valves have been poppet, ball or flapper designs. Since the poppet design does not lend it self to full-bore access, it wiii not be discussed in this paper.

When designing a wireline retrievable safety valve, the OD would normality be the starting point and would be determined by the tubing or other tubing accessories; the ID becomes a by-product of design. When designing a tubing-retrievable valve, the ID is the starting point and is determined by the tubing or associated tubing accessories; the OD becomes a by-product of the design.

When designing a wireline safety valve, the engineer?s goal during the design process is to maximize the valve?s bore ID to achieve the largest possible throughput for maximizing production rates and through bore access. Similarly, when designing a tubing retrievable subsurface safety valve, the goal is to minimize the valve?s OD. The OD of the tubing retrievable subsurface safety valves can have significant impact on the completion design. Typically, the tubing-retrievable safety valve is the component in the tubing string with the largest OD; therefore, it etermines the casing ID requirements. The term, "OD / ID ratio" will be used throughout the paper, and as such, its usage will always relate to the annular wall requirements to house the components of the TRSV. The thinner the annular wall requirement, the smaller the OD/ ID ratio will be.

All examples discussed in this paper will relate to tubing-retrievable safety valve (TRSV) design; however, all technologies presented are equally applicable towireline safety valve design.