2. 2
Gravel Pack Introduction
Potential sand producer formation:
Marine deposited sands, most oil and gas reservoir sands,
are often cemented with calcareous or siliceous minerals
and may be strongly consolidated. In contrast, Miocene or
younger sands are often unconsolidated or only partially
consolidated with soft clay or silt and are structurally
weak. These weak formations may not restrain grain
movement, and produce sand along with the fluids
especially at high rates.
Reasons, sands start producing:
Fluid movement causes stresses on the sand grains
because of the fluid pressure differences, fluid friction and
overburden pressures. If these stresses exceed the
formation-restraining forces, then the sand will move and
be produced.
Rapid changes in flow rates and fluid properties cause
unstable conditions which can result in increased sand
production.
3. 3
Consequences of Sand Production:
Production interruptions can be caused by sand plugging
the casing, tubing, flow lines and separators.
Casing collapse can be caused by changes in overburden
pressures and stresses in the formation.
Down hole and surface equipment can be destroyed,
downtime and replacement costs, spills and in extreme
cases a blowout.
Disposal of produced sands is costly.
4. 4
In Cased hole:
Reservoirs that produce sands:
Carbonate with particles and Non-Cemented Sand Stone
reservoirs produce sands.
After a while, lack of sands in their original spot in
formation shapes a cave or free space in the formation.
This space then allows an increase in fluid velocity toward
the set screen. Higher fluid velocity containing sands
results in erosion in the screen and decreases its working
life by passing thru screen surface.
This is also considered as gravel pack advantage vs.
standalone screen.
5. 5
In Open hole:
Since in open hole sands are non-homogeneous, finer
sands will pass the screens and come up to the surface.
These sands are filling up the vessels in production units
and reduce their performance.
Our suggestion is gravel pack to maintain high
production facilities’ performance for a longer period.
Steps in open hole:
Gravel pack system installation
Gravel pack the zone
Wash the mud 1- In order to increase the
production rate
2- Mud cake removal
In Open hole:
Results: 1- Blocking fine sands in the formation and
preventing them from movement
2- Avoid screen erosion
3- Preventing screen collapse
6. 6
Calculation
D = (5 or 6) D
D = the mean diameter of the gravel
D = the diameter of the formation grains at the
50 % weight
Volume of Gravel required:
Tot V = V of screen in casing + V of blank in casing + V of blank in tubing
= (ID Casing) 2 – (OD Screen) 2 (0.005454) cf / ft + ……
7. 7
Gravel Pack Assembly
Tool String from top to bottom:
Hydraulic setting tool Accessories
Packer Ball Seat
Sand Diverter Seal Tubes
Seal bore housing Centralizer
Shear joint
Blank pipe
Screen
Bull plug (Or wash down shoe)
See the figures on the next pages
8. 8
Hydraulic Setting Tool
Hydraulic setting tool Parts:
1. Working cylinder & piston to set the PKR
2. Seat & Ball Mechanism to maintain needed pressure to set
the PKR
3. Seal Tube Mechanism to Guide Carrier Fluid & Sand Gravels
behind the Screens
4. Contingency Release Mechanism
Note: The HST is being inserted in the packer in the shop.
9. 9
Packer
Objective:
1- To isolate the Annulus
2- Hang off the Sand Control Assembly
Caged Slip Packer Elements
Steps while packer is getting set:
Setting tool’s cylinders applies force on upper receptacle
Shear screws will shear and rubbers start swelling and blocking off
the way
At the same time slips come out and engaged to Casing
Packer is now set and is attached to Casing in two points by its robust rubbers
and slips.
10. 10
Seat Ball
Objective: In order to raise the pressure up to the PKR
setting and HST releasing points.
How many Seat ball is in an assembly:
1.Primary seat ball: Positioned below the window, to
guide the slurry out from the window.
2.Secondary seat ball: Positioned above the window,
for contingency release of HST
Seat ball is a narrowed portion on the assembly below and
above the window, so we can block off the way with a ball
dropped from surface.
Dump window and seat ball
11. 11
Sand Diverter
Objective: To provide pass for Circulation and reverse
circulation operation
By polling a little up, sand diverter moves and blocks the
window and opens another window above packer.
12. 12
Shear Joint
Objective: To disconnect the packer from the screen
assembly.
In case packer failed to set up properly we can disconnect
it from the screen assembly at shear joint.
Why not fish the whole tool string? Packer is not strong
enough to hold the rest, so the solution is to shear the
packer from the rest and do the fishing in two separate
parts as below.
1.Shear the packer from the rest at shear joint, fish the
setting tool and packer.
2.Fish the blank pipes and screens
13. 13
Blank Pipe and Screen
Blank pipe: To cover the non-productive zone
Screen: To be located in front of the perforation zone
(productive zone)
14. 14
Centralizer and Bull plug
Centralizer: Centralizes the screens inside the Production
Casing (Makes uniform Annulus for Gravels)
Bull Plug: Blocks the string end
15. 15
Job steps
• RIH with Sand Control Assembly to the desired depth
• Drop the ball to sit on seat ball
• Circulate to push the ball thru work string till it gets on
the Ball Seat, ( Fall time depends on depth )
• Pressure up the string
• Set the PKR by applying 2800 psi
• Rig up the Pump Lines on the Annulus, test the PKR
with 500 psi
• Release the HST by applying 3500 psi
• Continue Pressure Up the string to 4400 psi to open
the windows on the Sand Diverter
• Start pumping Slurry (Carrier Fluid +Gravel Sand) thru
the working string (Slurry will go out of the tool from
the window to the annular between the screen and
casing and fill it up till getting the screen out)
• POOH the working string
