VXTe Deepwater Tree Development – Cost and Risk Reduction Through New and Advanced Technology

Abstract

Abstract The oil and gas industry continues to face low energy prices, which has pushed manufacturers to re-think conventional designs and methods that may not be at the efficiency levels required to operate under today’s environmental and economic conditions. This paper describes the development of a new and advanced subsea tree technology that reduces equipment cost and installation time, thereby reducing risk and adding significant value to the end user. Traditional completion systems have become increasingly complex as efforts were made to address individual problems as they arose. These challenges included wellhead interfaces capable of handling the stack-up tolerances of casing hangers, and a need to orient the tubing hanger relative to a flowline connection system. The solution utilized by most conventional systems was the incorporation of a tubing head spool or some other elaborate means of orienting within the BOP, which created the need for temporary well barriers, required costly workover riser systems and wireline trips, and ultimately led to concentric bore systems with annulus valves located on a tubing head spool. The VXTe subsea tree system solves the problems associated with wellhead stack-up tolerances and orientation of the tubing hanger, in a simple, robust and elegant manner. The simplicity of the system allows the tubing hanger to be installed like a casing hanger. In this way, the drilling and completion operations may be undertaken without the cost and safety concerns normally associated with temporary well suspensions or BOP trips, and the orientation requirements for flowline connections are completely decoupled from the tubing hanger installation. The requirement for well barriers is also eliminated, thereby trimming the costs of additional spools, and further eliminating leak paths and failure modes. By eliminating the cumbersome solutions employed by conventional systems, our system also eliminates the need for the extensive SIT testing required to validate working interfaces. The VXTe system is a simple, robust and elegant answer to the industry's most pressing subsea tree challenges and aligns with the IOGP requirements agreed upon by most of the major operators. The VXTe system has undergone a number of verification analysis and validation testing adhering to API standards. In addition to meeting applicable API testing requirements, additional cycle testing was performed to validate the performance of the system over the anticipated life cycle. This included installation and removal cycle testing in addition to pressure and temperature testing. The design details, analysis, and test results will be presented.