well_control_equipment

Well Control Equipment n

Surface & Subsea BOP Equipment – BOP annular and rams. – Choke Manifold / Chokes. – Accumulator unit and hydraulic lines.

n

Mud Gas Separator.

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Drill string valves.

n

Diverter.

Well Control Equipment At the end of this section you should be able to: n

Identify surface and subsea blowout preventors and equipment.

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Identify additional well control equipment at the rig site, and describe their functions.

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Identify drill string valves and describe their functions.

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Identify the diverter equipment.

Well Control Equipment If primary well control is lost*, the BOPs are closed and the well control equipment and techniques are used to control the well. The proper selection and utilization of the blowout preventers, chokes, choke manifolds, mud-gas separators, degassers, mud-monitoring equipment and all other well control related equipment is an important aspect of well control. Among the main factors affecting the selection of well control equipment, there are: Pressure: working pressure rating must exceed the maximum anticipated surface pressure. n Temperature: rating of all elastomers (BOP rams, annular preventer bags, bonnets, valves, marine riser, kill/choke line connections, etc). n Nature of well fluids: such as the presence of H2S. n Fluid compatibility: the resistance of elastomers to OBM and completion fluid. n

*Primary well control is achieved by controlling formation pressures with the hydrostatic pressure of the drilling fluid.

Surface BOP Stack The BOP stack is located over the well head and under drill floor in surface BOP’s. They might include: Pipe ram preventer. n Drilling spool. n Blind/shear ram preventer. n Casing head housing. n

The BOP’s is assembled in many arrangements depending upon requirements.

ANNULAR TOP RAMS BLIND RAMS

Choke line HCR

Kill line BOTTOM RAMS

BOTTOM RAMS

VR plug may be installed in casing head

Subsea BOP Stack

BOP Stack The BOP stack consists of several valves, called preventers, stacked on top of each other. There are two kinds of preventers: annular preventer and ram preventers. n

Annular Preventer. – Close/seal on any object in the wellbore. – Sizes from 7-1/16 to 29-1/2 in. – Pressures from 2K to 20K psi – Often called “the Hydrill”

BOP Stack Ram Preventers: n

Pipe Rams: – Fit a specific pipe size. – Need pipe to make a seal. – Reliable and field proven. – Only hold pressure from bottom.

n

Shear/Blind Rams: – Both shears drill pipe and seals the hole. – Capacity to cut through 5” drill pipe. – Emergency equipment. – Top seal and side packers. – Can seal on open hole.

Top seal

Side Packers

Large frontal area

Choke Manifold The choke manifold is made up of special high-pressure piping and valves. The choke manifold and chokes are used to circulate formation fluids out of the well in a controlled manner. Fluid returning from the well flows from the BOP stack to the choke manifold through a choke line. Functions: n Restrict flow to maintain back pressure, to prevent further influx. n Divert fluid from well. The choke can be opened and closed from the rig floor using the choke control panel.

Accumulator The accumulator unit pressurizes hydraulic fluid and stores it at high pressure to provide hydraulic energy to operate the BOPs.

Mud Gas Separator

Mud

GAS

Vent line No valves!!

d D

Drain line w/valve

1. Diameter and length controls the amount of pressure in separator Baffle plates

Impingement plate

Siphon breaker

No valves!!

The mud-gas separator is a low-pressure vessel that removes gas from returning drilling fluid. Proper design and efficiency of the mud-gas separator is very important to ensure that drilling fluid is not carrying flammable gas to confined areas or mud tanks where rig personnel are working.

From choke

MUD

2. Height and diameter and internal design control separation efficiency

3. Height of ‘U’-Tube (D) and distance from bottom of separator to top of ‘U’Tube (d) controls fluid level and stops gas from going out of the bottom

Drill String Valves Used to prevent the formation fluids going up the drill string. Different types of drill string valves are: n n

Full Opening Safety Valve: installed on top of the drill string when a kick is taken whilst tripping. Inside BOP: one-way valves that allow flow from drill string to annulus but not from annulus to drill string. An example is the float valve (flapper or ball valves), installed just above the bit.

Full opening safety valve

Float valves

Diverter The diverter system is not an element of the well control equipment, it is not intended to shut-in or halt well flow. The diverter system, provides a low-pressure flow control system to direct controlled or uncontrolled wellbore fluids away from the immediate drilling area for the safety of personnel and equipment, while drilling surface hole (prior to setting the surface casing on which the BOP stack and choke manifold will be installed). Drilling string Flow line Diverter Diverter line

Surface

Riser

Full opening valve (interlocked)

Conductor Casing shoe Surface hole Influx