Enhanced Reliability with Unique Tubing-Retrievable Safety Valve Design

Abstract

Tubing-retrievable safety valve (TRSV) performance has been improveddrastically over the last decade as a result of simplified design concepts, increased use of non-elastomeric and metal-to-metal (M-t-M) sealing materials, and enhanced validation testing. At the same time, the demands imposed bydeep-water, high-pressure/high-temperature (HPHT) environments, high-flow-rategas reservoirs and remote subsea applications have also increased, and in spiteof continuing improvement in safety-valve technology, equipment has continuedto be pushed to its limits. As a result, higher valve-opening pressuresassociated with deep-set applications have emerged, and to address these needs, conventional solutions have focused on balancing the wellbore and its reactionto the hydraulic piston area using mechanisms that require additional sealsand/or gas-charged chambers. These solutions are heavily dependent onelastomeric seals and/or the permanent, long-term containment of a dome (gas)charge or pressure counterbalance, to maintain reliability. Unfortunately, dynamic elastomeric seals have posed a major limitation when design intentfocuses on equipment that will provide enhanced life-of-the-wellreliability. This paper will review a unique TRSV design that is a revolutionary newconcept. This design incorporates a floating magnetic coupler that allows thehydraulic actuator to be positioned in a dedicated chamber isolated fromcontact with well fluids and pressure. Since the hydraulic actuator has beenseparated from the tubing wellbore, this new valve is the first in the industryto have 100% M-t-M sealing with no moving seals within the tubing wellbore. The new intrinsically simple design:Increases environmental and personnel safetyReduces system costsReduces sealing requirementsProvides an extremely reliable tubing retrievable safety valveEnhances life-of-the-well. Introduction The development of hydrocarbon recovery methods has occurred in phases thatfor the most part have been driven by technological advancements. For example, shelf development in the US (GOM) began with the first producing well out ofthe sight of land being completed in 1947. This feat was enabled by thecapability to construct a well jacket to contain and protect the well. Thistechnology climaxed with large platforms that contained numerous well slots setin water depths up to 2000 feet. The advent of 3D seismic techniques led to further development anddevelopment of shelf properties. By using 3D seismic tools, developers wereable to identify greater depths in oil and gas prospects. Aided by this newtechnology, smaller companies identified a niche in sub-salt pay fields. In the mid-1990's, deeper fields were reached with subsea completions. Inaddition to the ever increasing depths made available by subsea completions, tension leg platforms (TLP) and new completion techniques wereintroduced.1,2 These advancements place ever deeper prospects withinreach of this new technology. These ongoing developments have resulted in deepwater prospects becoming theprimary driver of capital expenditures, and deepwater activity is now a majorpart of the oil and gas industry throughout the world. As a result of thistrend, completion equipment has been subjected to more corrosive and demandingHP/HT conditions.3,4 In addition to current deepwater development, 3D seismic analysis has turnedup other indicators that are of interest to the oil industry, and these arecurrently being investigated. While promising superior production capabilities, these deeper targets will further challenge technology. With reservoir depthsas deep as 40,000 feet, bottomhole temperatures above 400°F, and bottomholepressures approaching 30,000 psi, new equipment will be required to drill andcomplete these potential "super" wells. The demanding conditions of deep-water, HP/HT), high- flow-rate gasreservoirs and remote subsea applications challenge the integrity of allequipment in these environments. These conditions place a particularlystringent challenge on surface-controlled subsurface safety valve (SCSSV)designs and demands equipment that outperforms the capabilities of conventionalSCSSV designs.