What Are the Functions of a Subsea Test Tree?

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There are many different subsea test trees, and knowing which ones are best for your specific needs can be challenging. In this article, we’ll go over the various types and functions and their cost and design. If you’re planning on installing a subsea test tree, read on to understand better what these devices are capable of.

Functions

The subsea test tree is a piece of equipment that is often used in subsea applications. It is typically comprised of an umbilical system and a subsea controller. An umbilical cable connects these components to the subsea wellhead assembly, which is located above the production tree. The tree serves as an isolation device and provides access for well intervention operations.

The upper body portion 90 of a subsea test tree 44 is acoustically coupled to the excellent test string 34. The upper portion 190 is a hydraulically powered latch, and it responds to acoustic commands to connect and disconnect the two parts. A subsea test tree separates the upper and lower bodies. In addition, the subsea test tree 44 has a subsea connector 91 and a control box 102 for the test instrumentation.

Types

There are several different types of subsea test trees. The subsea test tree you use depends on what the job requires. The material rating you choose will influence whether the tree is suitable for a particular reservoir or not. Temperature ratings are listed on API 6A and include K, P, R, S, T, and U. While temperature ratings affect the price of a subsea test tree, their impact is minimal. Choosing the material rating depends mainly on the characteristics of the reservoir, and the material rating has little influence on tree procurement costs.

Several types of subsea test trees include conventional, dual, mono, and through-bore. In addition, some trees provide other functions, such as well intervention means, chemical injection points, flow rate, flow composition feedback, valve position feedback, and sensor outputs. Typically, subsea trees are used on subsea wells because they are flexible and can be installed without downhole completion. You can also learn more at PRT Offshore.

Costs

Submarine test trees are typically built with dual bores. They include the primary production bore with two series ball valves (26, 28) and an annulus bore with one ball valve (30). The test tree has a remotely operated vehicle override system that allows for the remote operation of each valve. The costs of a submarine test tree depend on its configuration and the number of valves. One subsea test tree is typically two-thirds of the total cost.

The completion subsea test tree can include multiple valves, including flapper and plug valves. In a deep-water application, a retainer valve is required to prevent sudden releases of high-pressure gas into the marine riser. If the submarine is not equipped with a retainer valve, it could collapse in the event of an emergency disconnection. The lower marine riser package is disconnected from the BOP stack, and wireline plugs are installed and tested. The tree assembly is then performed.

Design

A submarine design process starts with structural design. This portion of the process takes up 40 percent of the entire design process. It focuses on strength factors and functional aspects. Designing a submarine that can resist the pressure of an explosion is essential for the safety and reliability of the ship. Submarines are exposed to a wide range of stresses. For this reason, they must be able to withstand shock waves and vibrations.

The design of the test tree is critical in determining whether a sub’s hull and other structures will maintain their integrity. For example, while failure modes 1 and 2 were local failures, failure mode three consisted of buckling along the entire pressure hull length. The buckling extends from the transverse rings to the size of the submarine. This condition is known as the total collapse of the submarine. It can occur due to insufficient material strength or a submarine diving to depths beyond the collapse depth.

Disconnection capabilities

A submarine test tree (SSTT) is a subsea testing structure installed above the lowermost BOP stack 120 ram and below the blind/shear ram 130. It is accessible through port A12 (shown in FIG. 12A). The communication path to a submarine test tree is illustrated by arrows AP. Generally, a submarine test tree is connected to the BOP stack using a tubing-based landing string LS. You can use this landing string with a very small tubing hanger TH12.

Electric conduits are typically routed through various components, including ram and annular seal spools, subsea test tree latch devices, emergency disconnect mechanisms, and E/H control modules. Umbilicals are also used in submarine test trees. These components are essential for the operation of ballistic missile submarines. In addition to providing power, these devices also offer protection from the effects of electromagnetic fields, water, and other factors that can reduce their effectiveness.