Maintaining control of a well during the completion and workover phases may be more complicated than well control in drilling operations. Additional complications may exist as, a) various types of workover fluids ranging from low-density diesel to high-density brine fluids may be used; b) interrelated activities may occur simultaneously, such as workovers on a platform with producing wells.
Saudi Aramco has four (4) classes of BOP arrangements for workover operations. The workover program shall specify the Class BOP stack (not individual components) to be used.
9.0 CLASS ‘I’ 2,000 PSI WORKOVER STACK
9.1 Usage:
This class of BOP Stack is used on water supply wells and shallow, low-pressure aquifer observation wells, where the operation to be performed on the well and/or space below the rig substructure precludes use of ram-type preventers. NOTE: This class of BOP stack with a working pressure of 2,000 psi is not defined in Table 1.1; any given 21-1/4” Annular is typically rated to 2,000 psi and it may be used on wells with a MASP of up to 1,600 psi.
9.2 Class ‘I’ 2,000 psi Workover BOP Stack Arrangement:
9.2.1 The minimum equipment required will be a Hydril, Cameron, or NOV Shaffer annular type preventer with a working pressure of 2,000 psi or greater. A 2” kill and/or fill-up line shall be connected to the landing base side outlet as shown in Figure B-10.
9.2.2 When sufficient space below the rig substructure is available, a Power Water Injection Tree (ball valve) shall be used below the annular, as shown in Figure B-9.
9.2.3 The annular preventer will be visually inspected and functionally tested prior to installation and pressure tested after installation using a cup-type tester set at a depth of approximately 60’. Test pressures, to be specified in the workover program, shall be greater than the MASP, but shall not exceed 80% of the rated casing burst.
Figure B-9: Class 'I' Workover BOP Stack
10.0 CLASS ‘II’ 3000 PSI WORKOVER STACK
10.1 Usage:
This class BOP stack is used on most onshore workovers to be performed on producing, water injection and reservoir observation wells. These wells are normally low-pressure and equipped with up to 3,000 psi WP wellhead equipment.
10.2 Class ‘II’ 3,000 psi Workover BOP Stack Arrangement:
This BOP stack is identical to the Class ‘C’ Drilling stack as described in Section 7 above. Please note that if SBR’s are not being used, in special circumstances (such as low sub-structure height) it is permissible to leave out the drilling spool and use the BOP side outlets for line connections.
11.0 CLASS ‘III’ 5,000 PSI WORKOVER STACK
11.1 Usage:
This class BOP is used on all offshore workovers with wellhead equipment rated to 3,000 or 5,000 psi and onshore workovers with wellhead equipment rated to up to 5,000 psi.
11.2 Class ‘III’ 5,000 psi Workover BOP Stack Arrangement:
This BOP stack is identical to the Class ‘A’ 5,000 psi Drilling stack as described in Section 4 and Figure B-5 above.
12.0 CLASS ‘IV’ 10,000 PSI WORKOVER STACK
12.1 Usage:
This class BOP is used on all workovers with up to 10,000 psi WP wellhead equipment.
12.2 Class ‘IV’ 10,000 psi Workover BOP Stack Arrangement:
The Class IV 10,000 psi workover stack is arranged the same as the Class ‘A’ 10,000 psi drilling stack. All BOP equipment in this stack shall be 11” (or larger) 10M rated working pressure, including the annular preventer. NOTE: The annular shall be 10,000 psi working pressure. All other equipment requirements are as previously discussed in Section 3.0.
13.0 CLASS ‘V’ 15,000 PSI WORKOVER STACK
13.1 Usage:
This class BOP is used on all workovers with up to 15,000 psi WP wellhead equipment.
13.2 Class ‘V’ 15,000 psi Workover BOP Stack Arrangement:
The Class V 15,000 psi workover stack is arranged the same as the Class ‘A’ 15,000 psi drilling stack. All BOP equipment in this stack shall be 11” (or larger to provide full opening to the tubing spool and production casing) 15M rated working pressure, except the annular preventer WHICH shall be 10,000 psi working pressure. All other equipment requirements are as previously discussed in Section 2.0.
14.0 SPECIAL WELL OPERATIONS BOP STACKS
The following represents Drilling and Workover’s minimum BOP equipment requirements for coil tubing, snubbing, and wireline operations. In some cases, the service company’s internal policy may exceed these BOP requirements.
14.1 BOP Equipment Requirements for Coil Tubing Operations:
BOP equipment requirements for low-pressure, high-pressure and critical well service coil tubing (CT) operations are shown in Figures B-10, B-11 and B-12, respectively. Selecting the BOP arrangement shall be based on the maximum anticipated operating or shut-in wellhead pressure.
These arrangements are for standard CT operations and should be modified as needed for special or unusual applications.
14.1.1 Low-Pressure Coiled Tubing BOP Equipment Requirements
The low-pressure or standard arrangement (less than 5,000 psi WHP) includes 4 sets of rams: tubing rams on the bottom in the #1 position, slip type rams in the #2 position, cutter
rams in the #3 position and blind rams on top in the #4 position. In addition, there is a flow cross with a valve installed below the cross. See Figure B-10.
Figure B-10: Low Pressure Coil Tubing BOP Stack
Low-pressure stacks shall comply with the following minimum requirements:
All equipment shall meet or exceed NACE MR-01-75 and API Standards for well control
Rated WP greater than the maximum anticipated well pressure
Side-door stripper
Minimum BOP configuration of blind, shear, slip, and pipe rams
Kill line with minimum 2-1/16” flanged connection
Flow cross with flanged outlets and double valves
Ability to monitor wellhead pressure below the pipe rams with isolator
Slip design that will minimize fatigue/deformation damage to the coil
QUAD BO SIDE DOOR STRIP
BLIND
SHEAR
SLIP
PIPE
ES46 DSA6
GATE VALVE
SIDE DOOR STRIPPER
QUAD BOP SIDE DOOR
STRIPPER
Slip rams capable of holding the pipe up to the yield point with maximum rated WP in a hang-off mode
Accumulator shall be sized to operate all BOPE (close-open-close) at maximum rated WP
14.1.2 High-Pressure (HP) and Critical Well Service (CWS) Coiled Tubing BOP Equipment Requirements
The high-pressure arrangement (greater than 5,000 psi WHP) includes the same equipment as in the low-pressure arrangement, plus a combination BOP containing a second set shear/seal rams and a set of pipe/slip rams when flowing the well with coil tubing in the hole (i.e. treating or production logging). A second stripper is also required when treating or production logging. See Figure B-11.
Figure B-11: High Pressure Coil Tubing BOP Stack
QUAD