Annular Preventers

1.3.1 Annular Closing Times

  • API RP53 state that surface annular preventers closing times should not exceed 30 seconds for smaller than 18 3/4" and 45 seconds for 18 3/4" and larger.
  • Subsea annular preveters should not exceed 60 seconds.

1.3.2 Shaffer Spherical BOP

Shaffer annular BOPs are rugged, compact and will seal on almost any shape or size- Kelly's, drill pipes, tool joints, drill collars, casing or wireline. They also provide positive pressure control for stripping drill pipe into and out of the hole. The annular BOP is one of the first lines of defence in controlling a kicking well. When the BOP is actuated, hydraulic pressure operates, and in turns closes the spherical shaped preventer. The closure occurs in a smooth upward and inward motion, as opposed to horizontal motion. The spherical geometry reduces the internal stresses and the friction between the sealing element and the BOP body. Steel segments reinforce the sealing element without protruding into the wellbore when the element is open. The spherical design operates with a lower operating pressure, reducing the number of accumulators and is available in 1,000 to 10,000 psi working pressure with bore sizes from 4 1/16" to 30".

Locking Ring

Locking Wedge

Opening Hydraulic Connection

Closing Hydraulic Connection

Locking Ring

Locking Wedge

Opening Hydraulic Connection

Closing Hydraulic Connection

Bop Accumulator Bottles

Upper Housing

Element Adapter Ring Opening Chamber Piston

Lower Housing

Figure 19 - Shaffer Spherical BOP

Upper Housing

Element Adapter Ring Opening Chamber Piston

Lower Housing

Figure 19 - Shaffer Spherical BOP

Special features include:

  • Rugged and reliable sealing element provides positive seal after hundreds of tests to full working pressure.
  • Strong and simple construction-only five major parts.
  • Simple hydraulic system-only two hydraulic connections are needed.
  • Wear rings on movable parts prevent metal-to-metal contact. This feature prolongs preventer life.
  • Suitable for H2S service.
  • Servicing is easy- Element can be changed without getting mud and grit into the hydraulic system.
  • Element design provides long stripping life.
Annular Stripping Bottle
Figure 20 - Installation Hook-up for Single Spherical BOP

A BOP operating and control system is required to activate the Shaffer spherical BOP. The recommended installation requires:

  1. A control line to the closing port.
  2. For stripping, an accumulator bottle in the closing line adjacent to the BOP. This bottle should be pre-charged to 500 psi for surface installations and 500 psi plus 45 psi per 100 ft of water depth for subsea installations.
  3. A control line to the opening port.
  4. A hydraulic regulator to allow adjustment of operating pressure to meet any given situation.

□ rillinq S Well Services Trai n in g

The hydraulic operating fluid should be hydraulic fluid similar to NL 100 with a viscosity between 200 and 300 SSU at 100 deg. This is mixed with freshwater and for freeze protection, ethylene glycol replaces some of the water in the mix. Sphericals have relatively simple operating requirements compared to other annulars. When closing on stationary pipe, 1,500 psi operating pressure is sufficient in most applications. The illustrations below shoe the closing action of the Shaffer spherical in sealing around drill pipe and across the bore when no drill string is present.

Closing action begins when hydraulic fluid is pumped into the closing chamber of the spherical BOP below the piston. As the piston rises, it pushes the element up, and the elements spherical shape causes it to close in at the top as it moves upwards.

The element seals around the drill string as the piston continue to rise. Steel segments in the element move into the well bore to support the rubber as it contains the well pressure

When there is no pipe in the preventer, continued upward movement of the piston forces the element to seal across the open bore. At complete shutoff, the steel segments provide ample support for the top portion of the rubber. This prevents the rubber from flowing or extruding excessively when confirming high well pressure.

Annulus Well
Figure 21

□ rilling & Well Services Training

Care must be taken when closing the preventer around casing. The chart below indicates the closing pressure adjustment required for safe closure on most common sizes of casing. Failure to take this into consideration could result in collapsing the casing during shut in.

HYDRAULIC CLOSING PRESSURES ON CASING

Spherical Size * (Inches)

Well pressure (psi)

Casing Size (Inches)

7

7 5/8

8 5/8

9 5/8

10 3/4

11 3/4

13 3/8

16

18 5/8

20

21 1/4

5,000

1,500

1,400

1,175

975

790

640

480

300

190

150

21 1/4

2,000

1,500

1,400

1,175

975

790

640

480

300

190

150

18 3/4

10,000

385

310

325

18 3/4

5,000

1,500

1,400

1,175

975

790

640

480

300

16 3/4

5,000

1,500

1,400

1,175

975

790

640

480

13 5/8

3,000/5,000

1,500

1,265

890

615

415

280

30

1,000

1,100

1,100

900

* Spherical sizes not listed above require no pressure adjustments when closing on casing.

Steel Segments moulded into the element partially close over the rubber to prevent excessive extrusion when sealing under high pressures. These segments retract when the element returns to the open position, even when the packing element is worn far beyond normal replacement condition.

Sealing elements are available in natural and Nitrile rubber compounds. This allows the spherical to be fitted for any type of service — Water base mud, oil base mud and operating temperature.

Exposure of the rubber compound to H2S will reduce its service life. The drilling fluids and should determine the selection of the rubber compound to be used in this application. Nitrile rubber is less susceptible than natural rubber to damage from H2S

Sealing Element Shaffer Bop

Figure 22 - Steel Segments

Steel Reinforcement Segments

Figure 22 - Steel Segments

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Responses

  • salvia
    How annular bop operates?
    8 years ago
  • bartolomeo
    How to pull pistion on shaffer bop's?
    8 years ago
  • Rina Trentini
    How long does it takes to shut in a shaffer bop?
    8 years ago
  • kifle
    Why does the annular BOP have a lower working pressure than the ram BOPS?
    7 years ago
  • ted diggle
    Which annular element tdo api recommend for stripping?
    7 years ago
  • bingo
    Is a shaffer spherical well bore assisted close?
    7 years ago
  • semolina
    What is the maximum recommended hydraulic closing pressure of most annular preventers?
    6 years ago
  • isotta
    What is the recommended closing pressure of shaffer 21 1/4" annular?
    6 years ago
  • Felix
    How an annular preventer opens and closes?
    6 years ago
  • iggi
    Does pressureizing an annular preventer damage it?
    6 years ago
  • Nina
    What is normal annular closing pressure?
    6 years ago
  • JUHANA
    What is the maximum allowable closing time for an 183/4" surface annular?
    4 years ago
  • Regolo
    How much closing pressure on 9.5 pipe for shaffer element?
    4 years ago
  • lavinia
    What is the api time for a annular to close?
    4 years ago
  • ebony
    What controls annular hydraulic pressure?
    3 years ago
  • stanislao lucciano
    How many seconds does a annular preventer takes to close?
    3 years ago
  • isengrim
    How long does it take to close a 20 inch annular bop?
    3 years ago
  • henry
    How to improve annular preventer closing time?
    3 years ago
  • marco
    Which pressure of annuler through strippping?
    2 years ago
  • Austin Grant
    How we know that annular preventer leak?
    2 years ago
  • stella
    How much hydraulic fluid does a shaffer annular take?
    2 years ago
  • Annukka Pekkanen
    What is closing time for close annular?
    11 months ago
  • ZEWDI
    How to hook up stripping bottle on BOP?
    9 months ago
  • christian
    Can you close the annular against pipe with control line?
    7 months ago
  • Kiara
    How many times can the annular preventer be used before it must be changed?
    6 months ago
  • matilde
    What is the operating pressure for BOP annular?
    5 months ago
  • Teija
    Can annular preventer seal without pipe?
    4 months ago
  • Rasmus
    Can shaffer annular fit in a townsend t90 annular?
    3 months ago
  • HUGO
    Why two annular preventers on subsea bops?
    3 months ago
  • Cottar
    How much fluid is required to close 3000 psi bop?
    1 month ago
  • jessica
    When is the the BOP annular closed?
    23 days ago
  • delmo
    How much preesure can annular preventer hold?
    23 days ago
  • rudigar
    HOW MUCH PRESSURE ON ANNUAR PRESSURE?
    18 days ago
  • robbie
    How much fluid does it take to shut a 11" 3000# townsend annnular?
    15 days ago

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