Safety Valve for Ultradeepwater Applications

Abstract

Abstract In recent years, offshore oil and gas exploration has continued to push into deeper and deeper waters, such as those in the Lower Tertiary fields of the Gulf of Mexico. As these field discoveries are being completed, the application requirements for safety valve installations are moving toward valves that can be set very deep, but still only require a relatively low operating pressure to control the valve. In traditional safety valve applications, operating pressures are sensitive to the wellbore pressure and are typically above those pressures to hold the valve in the open position. As the setting depth of these valves goes deeper, the operating pressures increase to a significant level such that umbilical and wellhead design and performance is detrimentally affected. As a result of these constraints that occur in deep, offshore fields, a safety valve solution is desired to provide an ability to minimize opening pressures by balancing tubing pressure in high-pressure/high-temperature (HP/HT) conditions, yet allow extreme valve setting depth capability without compromising operational characteristics such as high opening pressures or pressure-balanced pistons using long-term valve gas charge storage. This paper discusses a new surface-controlled, subsurface safety valve (SCSSV) that uses the low opening pressures of a tubing-pressure-insensitive safety valve, without gas-charged assisted closure or dual control lines for balanced line applications. This system enhances valve reliability by eliminating the need for pressure reversals across the valve’s critical actuating piston seals while maintaining tubing pressure insensitivity. This system provides for much deeper valve depth capabilities compared to the methods previously discussed and also allows the safety valve to account for annulus pressure buildup scenarios not possible in current SCSSV applications. This paper presents design and development considerations for a new SCSSV solution allowing ultradeep setting depths without closed volume gas charged spring techniques utilized in current deep-set SCSSV technology. Test results will demonstrate the features, benefits, and reliability of this new safety valve in reference to previously unattainable valve operating depths in aggressive subsea well designs or annulus pressure buildup scenarios.