Figure 1. Well Design

Date: 2015-10-07; view: 433.

This is the string, in which the well is completed and controlled.

Well equipment required for field operations includes: wellhead, valves and chokes, emergency shut down systems, blowout preventer, fluid tanks, separators, line heaters, dehydration equipment, gas sweetening equipment, compressors.

On wells where high formation pressure or presence of aggressive gases are expected, special control equipment should be installed above casing string or tubing spool before well completion. A set of such control equipment including valves and pressure gauges controls oil and gas flow from the well and is called Christmas tree, which is associated with its shape and high number of branches with valves on the tree trunk.

Christmas tree is the main component of wellhead equipment. Christmas tree is attached to casing. It is designed to hold casing and tubing strings, isolate or seal annulus between these strings, provide fluid access to all strings, control processes of fluid and gas injection and production by means of valves.

Standard Christmas tree assembly includes adaptor flange, master valve, flanged cross, top adaptor, secondary master valve, wing valve, and a choke.

Pressure gauges are installed on Christmas tree to measure pressure in annulus and tubing. When pressure values under different working conditions are known the well can be controlled much easier.