Screens for Frac Packing

• Screen types

• Screen characteristics that lead to failures

• Production and reservoir characteristics that

affect screen selection

Prepacked Screen – minimum thickness prepack

Prepacked liner with center screen – very durable but

plugs easily with fines.

A few things that cause screens

to fail……… • Running screens

– drag, sharp turns, windows, dope, shale,

• Pumping past screens

– erosion, pressure, screenouts

• Pumping through screens

– Fines in packing fluid, rate, volume

• Producing through screens

– Fines in drill-in fluid, mobile fines, pressure drop

• Compaction loads

Liquid

return to

surface

slurry Failure points in the flow path during frac

or gravel packing:

1. Crossover port

2. Casing opposite

crossover port.

3. The annular area between screen and

casing wall.

a. Erosion from high velocity linear flow

– minimal problem

b. Erosion from high velocity flow as

the slurry enters a perforation.

c. Pressure drop in this area during high

rate flow (fracs) can collapse screens

– problems are very rare, but watch

clearances.

Hole

Size

Vol of

solids in

the filter

cake

Wt of

solids

Size of

solids

cu. in./ft. lb/ft microns

4.5" 4.9 0.48 5 to 1000

6.125" 6.6 0.65 5 to 1000

Solid Debris in the Completion Interval from a

“Clean” Drill-In Fluid

Screen

Opening

Screen

Diam

Opening area

per linear ft of

screen

% of wall area

open to flow in a

wire wrap screen

0.008" 4 10.9 7%

Screen Opening – with and without prepack

% open in a

prepack

screen?

Maybe 1%, or

less?

Gravel Size Gravel mean

Max Pore

Size Gravel area

Max Pore

Area

Max Pore

Diam

mesh in. in. in.2 in.2 microns

20/40 0.0234 0.003656 0.0004301 0.0000105 93

40/60 0.0117 0.001828 0.0001075 0.00000262 46

Pore size of the gravel is the limiter.

Remember the 1/3rd to 1/7th bridging

rule?

Damage Potential in the Gravel Pores

How many fines in 1 gram of 44 micron (325 mesh) particles?

Over 1 million!

Flow Capacity of Clean Screen

0

2

4

6

8

10

12

0 5000 10000

Flow Rate, BPD/ft

Pre

ss

ure

Dro

p, p

si

2-3/8"

2-7/8"

3-1/2"

Area open to flow

• 7” casing,

– 4 spf (0.6” hole) = 0.4%

– 12 spf (1” hole) = 3.6%

– 25 slots per foot (0.020” x 3”) = 0.57%

– 72 drilled holes (0.5”) per foot = 5.4%

– wirewrap screens = 6 to >10%

– woven screens = 20 to 30%

Sand Control Damage – The

Reasons

• Skin damage

– Reservoir-to-wellbore limits

– Invasion of fines into gravel

– Crushing/breaking of gravel

• Physical Damage

– Screen Running Damage

– Erosion during production

– Corrosion – from produced and injected fluids

Physical Damage

• Screen Running Damage

• Erosion during production

• Corrosion –produced and injected fluids

Primary Erosion Locations

• Directly opposite perforations

• sharp turns in the flow path

• where gas velocity is maximum

• eddy current and similar patterns

• constrictions in the flow path

Erosion holes

opposite

perforations

Max Velocities for Particle Sizes

0

50

100

150

0 100 200 300

Particle size, u

ma

x v

el. f

/se

c

0.1 ft3/day

1 ft3/day

Maximum flowing fluid velocity for increasing particle diameters.

Although smaller particles do less damage than larger particles (less

mass), the sheer number of small particles can still do a significant

amount of damage.

Baker Excluder Screen Damage from Trinidad

01/28/98

Upper shroud removed. Notice that the major damage is on the seam.

This type of damage can occur anywhere where a hot spot develops.

Weave Damage on an Eroded Screen

Poui B-12xxx Screen

January, 1988 (5 of 6 pictures)

Hole in screen can be seen Erosion hole in screen, adjacent holes

were plugged with debris.

Multiple damage mechanisms – A typical failure cause is when

the flow areas begin plugging with debris, followed by very

high velocity flow through a few remaining open flow areas.

The high velocity flow is what drives the site specific erosion.

Design Learnings

1. Crossover ports should have an area at least as large as the tubing

area, preferably 130%.

2. Crossover ports should be shaped to assist the slurry direction

change and minimize turbulence.

3. The area of the screen/casing annulus should be 20% larger than the

tubing – keep pressure drop below about 500 psi/100 ft.

4. Zones with very high permeability streaks may bridge the annulus

with dehydrated sand plugs – special design is required.

5. Never stand screens in the derrick.

6. Use a screen table to run.

7. Adequate make-up room needed at joints, but minimize blanks

where voids may occur.

Screen Tensile Strength

Screen Type Break tensile load

2-7/8” wire wrap 100 to 112,000 lb

2-7/8” welded 102 to 115,000 lb

3-1/2” wire wrap 100 to 149,000 lb

3-1/2” welded 140 to 155,000 lb

2-7/8” slotted liner 100,000 lb

Screen Collapse Loads

Screen types Collapse Load

2-7/8” wire wrap >8,000 psi

2-7/8” welded 5 to 6,000 psi

3-1/2” wire wrap >8,000 psi

3-1/2” welded 5 to 6,000 psi

Collapse loads

• Critical during high rate circulation and frac

packing

• Screen crush resistance may be reduced by

mechanical loading

Some Database Learnings

• Screen type as a failure factor in frac

packing is overshadowed by:

– Running damage to the screen

– Screen-to-casing clearances

– And, “maybe” how pack is placed after frac.

What screen do we use?

• Most of them. Carefully.

• Factors:

– formation grain size and sorting,

– mobile fines,

– how much gravel reserve can be placed,

– clearances

Total

number

wells of

complet

ion type

Total

Well-

Years

Sand

Control

Design

Failure %

of

attempts

Sand

Control

Applications

failure %

of attempts

Sand

Control

Infant

Failure

% of

attempts

Sand

Control

Production

Failure

(failures /

well/yr

Type of Completion

Injectors (soft sand formations) 24 63 0 12.5 0 0.064

Screenless Fracs 7 44 0 0 0 0.046

Cased and Perfed 66 306 0.00 1.5 0.00 0.085

Screen Only Completion 183 783 0.55 0.0 0.55 0.056

Expandable Screens 194 255 1 3 1 0.016

Cased Hole Gravel Pack 369 1514 0.00 2.2 0.8 0.011

Open Hole Gravel Pack 175 507 0.00 9.7 0.57 0.020

High Rate Water Packs 187 544 0.00 0.5 0.53 0.009

Frac Pack 844 3369 1.69 2.4 0.24 0.004

total wells 2049 7277.8