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[4] [5] During drilling operations, complex accidents such as gas invasion and overflow are prone to occur. [6] In addition, deep strata have poor diagenesis , weak pressure bearing capacity, so leakage is easy to happen, the risk of well control is high, and the treatment is difficult, which impact on deepwater wellbore integrity seriously.
The primary safety control devices for well drilling are blowout preventers (BOPs), which have been used for nearly a century in control of oil well drilling on land. The BOP equipment technology has been adapted and used in offshore wells since the 1960s. The inspection and repair of subsea BOPs are much more costly, and the consequences of ...
This operation is typically undertaken when the bit (which is the tool used to crush or cut rock during drilling) becomes dull or broken, and no longer drills the rock efficiently. A typical drilling operation of deep oil or gas wells may require up to 8 or more trips of the drill string to replace a dull rotary bit for one well.
Subsea wells have pressure control equipment located on the seabed or between the riser pipe and drilling platform. Blowout preventers (BOPs) are the primary safety devices designed to maintain control of geologically driven well pressures. They contain hydraulic-powered cut-off mechanisms to stop the flow of hydrocarbons in the event of a loss ...
the drilling and operating companies well control policies. For workover or completion operations, other methods are often used. Bullheading is a common way to kill a well during workovers and completions operations but is not often used while drilling. Reverse circulation is another kill method used for workovers that are not used for drilling ...
Well completion is the process of making a well ready for production (or injection) after drilling operations. This principally involves preparing the bottom of the hole to the required specifications, running in the production tubing and its associated down hole tools as well as perforating and stimulating as required.
In a drilling context, these sources are used by trained personnel, and radiation exposure of those personnel is monitored. Usage is covered by licenses from International Atomic Energy Agency (IAEA) guidelines, SU or European Union protocols, and the Environment Agency in the UK.
The full name for this most common type of downhole safety valve is a Tubing Retrievable Surface Controlled Sub-Surface Valve, shortened in completion diagrams to TRSCSSV. If a tubing retrievable valve fails, rather than go to the expense of a workover, a "wireline retrievable" valve may be used instead.