The subsea wellhead system (Fig. 1) is a pressure-containing vessel that provides a means to hang off and seal off casing used in drilling the well. The wellhead also provides a profile to latch the subsea blowout preventer (BOP) stack and drilling riser back to the floating drilling rig.

What is the purpose of a wellhead?

The primary purpose of a wellhead is to provide the suspension point and pressure seals for the casing strings that run from the bottom of the hole sections to the surface pressure control equipment. While drilling the oil well, surface pressure control is provided by a blowout preventer (BOP).

What is wellhead system?

Wellhead systems serve as the termination point of casing and tubing strings. As such, these systems control pressure and provide access to the main bore of the casing or tubing or to the annulus.

How do subsea wells work?

A Subsea well is a well in which all the production systems are located on the seabed. The facilities which are under water are basically referred to as ‘Subsea’. The Christmas tree, basically the valves, pressure gauges and other equipment that control the flow of the fluid from the well are on the seabed itself.

Why is subsea well?

Subsea well systems are among most profitable offshore projects, worldwide. They allow maximum use of infrastructure and developing reserves that are too small to be economic by other production systems. Start-up times short are now short – normally less than 2 weeks. System availability over 99% is common.

What is the difference between a wellhead and Christmas tree?

Many times, the words Christmas Tree and Wellhead are used interchangeably; however, a wellhead and Christmas tree are entirely separate pieces of equipment. A wellhead must be present in order to utilize a Christmas tree and is used without a Christmas tree during drilling operations.

What are the components of a wellhead?

Generally, the wellhead consists of three components: (1) the casing head, (2) the tubing head, and (3) the Christmas tree. The casing head consists of heavy fittings that provide a seal between the casing and the surface.

What is a subsea manifold?

A manifold is an arrangement of piping and/or valves designed to combine, distribute, control, and often monitor fluid flow. Subsea manifolds are installed on the seabed within an array of wells to gather production fluids or to inject water or gas into wells.

What is a subsea tree?

Used on offshore oil and gas fields, a subsea tree monitors and controls the production of a subsea well. Fixed to the wellhead of a completed well, subsea trees can also manage fluids or gas injected into the well. Subsea trees are used in offshore field developments worldwide, from shallow to ultra-deepwaters.

How much does a wellhead cost?

The average wellhead price of crude oil decreased $2.51 to $33.41 in September 2020 from August 2020. The monthly average price was $16.87 lower than the average price of $50.28 in the same month last year.

What does subsea stand for?

The project pulling together ocean and space is called SUBSEA, which stands for Systematic Underwater Biogeochemical Science and Exploration Analog.

What is a subsea Xmas tree?

Subsea tree (wet trees) is a system of valves, flow paths, piping, and connectors installed on a subsea wellhead to contain and control the flow of fluid from a reservoir or from the surface by injection. Two type of subsea Christmas tree are vertical Christmas trees and horizontal Christmas trees.

Why is it called a subsea Christmas tree?

Subsea and surface trees are an assembly of valves stacked on top of each other, with various spools, pressure gauges and chokes around the valves to control production and flow. The various pieces of equipment decorated around the arrangement of valves gave rise to trees being compared to Christmas trees.

What is subsea engineering?

Subsea engineers develop, design and test and install long lasting, cost effective equipment and structures that are used below the surface of the sea, such as pipelines and wellheads. You may be called a subsea pipeline engineer.

What is subsea technology in oil and gas?

energy. Oil and gas fields reside beneath many inland waters and offshore areas around the world, and in the oil and gas industry the term subsea relates to the exploration, drilling and development of oil and gas fields in these underwater locations.