An important topic in the category of Production Engineering by a splendid teacher

1. SAND CONTROL
Production Operations

2. SOME BASICS
 Sometimes once the well is fully completed, further stimulation is
necessary to achieve the planned productivity.
 Because perforation or the completion method may have
impaired the well.
 Let us review the various completions methods before we
discuss:
• Well Stimulation is a:
– A possible solution to an impaired (high skin) well
– A possible way to generate a negative skin in an unimpaired
well.

3. •Select the correct size tubing i.e. optimum over a given period. It’s unlikely
for the same tubing to last the complete life of the well and artificial lift will
be required at some point.
•Casing is cemented in place. If integrity is impaired it can be very expensive
to correct.
•All flowing wells must have some form of shutoff in the event of loss of
wellhead integrity e.g. sabotage, fire etc.
•Depending on the characteristics of the produced fluids some form of
chemical dosing may be required downhole
•It is essential for bottom hole data to be made available to reservoir
engineers
•Very often a well produces from more than one reservoir
The Optimum Well & Completion Design

4. Well Completion Functionality
Basic Requirements:
•Connect reservoir to well - perforations or open hole
•Protect the casing - tubing & packer
•Bring fluids to surface - natural flow or artificial lift
•Safeguard the well - Xmas tree & SCSSV (Surface Controlled Subsurface Safety Valve)
•Control sand - gravel pack, sand screens or sand consolidation
•Zonal isolation - packers or monobore
•Costs - fit for purpose over life cycle of well

5. Above all, produce safely............

6. • A monobore completion is a
completion with fullbore
access across the payzone,
without diameter restrictions.
• This makes entering the well
with wireline or coiled tubing
much simpler, lowering risk of
problems and so reducing life
cycle cost.
Casing
Tubing
Packer
Liner hanger
Liner
Perforations
Monobore Completion

7. Allows production
independently from
two zones
Dual Completions

8. A Petroleum Technologist should ask the Question:
Do we expect any sand from the well?
If so how much and when?
What are we going to do to stop it?
 Sand production occurs when the overburden stresses
round perforations or the wellbore exceed the sand strength.
 The overburden stress increases with drawdown as the
reservoir pressure helping to support the rock
decreases.
Sand Control

9. Sand Production
Sand production leads to numerous problems
– erosion of downhole tubulars
– erosion of valves, fittings and flowlines
– clogging of surface process equipment
– the well-bore filling-up with sand
– collapsed casing as a result of lack of formation support.
– disposal problems particularly in offshore fields
So:Sand Prediction, andControl is a keyrequirement in many
fields:

10. Predicting Sand Production
• “FIST” is the Shell in-house sand prediction tool and uses core
strength data, and log strength data (sonic logs, porosity logs)
to predict a failure envelope.
• The envelope indicates at what conditions of a drawdown and
reservoir pressure sand failure may occur and under what
conditions sand production may become excessive.
PT (petroleum technologist) uses a programme called FIST (Fully Integrated
Sand prediction Tool). The input consists of core and log measurements of
rock properties.

11. Sand Control Techniques
Passive approaches
Maintenance and workover
Rate exclusion
Selective completion practices
Active approaches
Chemical consolidation
High energy resin placement
Consolidated gravel
Slotted liners or screens
Gravel packing
Frac & Pack

12. Barefoot
Perforated
Cased Hole
Completion Types with no Sand Control

13. Sand Control Screens
• Slotted liner or screen provides
a down hole filter
• Sand “bridges” on holes in the
screens while production flows
through.
• Sand production is often not
prevented by screens and
failure/erosion can still be a
problem
Bridging
With Well
Sorted Material
Plugging a problem
With Poorly
Sorted Material

14. Screens work like filters and are designed in such a way
that the slot opening is twice the median grain diameter, so
that particles bridge over the opening.
In this way, the particles don’t plug the slot, but leave
sufficient porosity open between the particles to allow flow
into the screen.
It may mean that some sand is produced until the
bridging is established.

15. However, if the particles are poorly sorted, then the pore
spaces may be plugged off by smaller particles leading to
lower productivity.
When screens are used in horizontal wells, the annulus is
open, which makes it difficult to do any remedial work on
the formation like pumping acid to stimulate production or
dissolve filter cake.
However, running screens in open hole is cheaper than
running casing, cementing it in place & then perforating.

16. Wire Wrapped Screen Prepacked Screen Excluder Screen
Screen Types

17. Expandable Screen/Slotted Tubular
A pipe has overlapping slots cut into it and is expanded by pulling or pushing a cone
through the screen. It easily opens up forming a tight fit with the casing or hole. A much
finer slotted tubular is sandwiched between 2 normal slotted tubulars in order to have a
small slot width for sand control.

18. • Historically, the most
widely applied sand
control technique
• Uses high permeability
gravel in conjunction with
slotted liner or screen
• Specially sized gravel is
packed into perforations
and annulus to stabilize
formation
Cased Hole
Gravel Pack
Open Hole
Gravel Pack
Gravel Packing

19. Gravel packing is basically a downhole filter to stop sand
production.
It should work better than just a downhole screen, because
gravel pack sand (rounded sand particles in range of 200 - 1200
microns in diameter) is pumped into the annulus between the
screen and the formation (see next slide for a close-up).
The gravel pack sand is squeezed against the formation sand
to stop it moving and ensures good sand control, with reduced
risk of plugging.
Gravel Packing

20. Formation
Perforations
Cement
Gravel
Casing
Wire
Wrapped
Screen
Internal Gravel Pack

21. Internal Gravel Pack
The gravel pack sand is made of rounded sand particles in range of 200 - 1200
microns in diameter). The sand grains should be well rounded and similar in
size, with <1% fine particles, so that there is maximum permeability through
the gravel pack.
Normally a wire-wrapped screen is used as this has a larger inflow surface
area. The gravel is transported using a carrier fluid which can be brine or a
viscosified (HEC) brine solution. The mixture is called a slurry.
Ideally, you need high viscosity & good carrying capacity in low shear regimes
(in the tubing) and low viscosity when the fluid is being injected into the
formation (low viscosity gives better injectivity).

22. • Goal is to inject plastic resins into the formation to
provide increased compressive strength while
maintaining acceptable permeability
• Treatment objective are:
– Cover entire perforated interval
– Coat all sand grains
– Concentrate resin at contact points
– Leave pore spaces open
• Three types of resins systems available:
– Epoxies
– Furans (and furan/phenolic blends)
– Phenolics
2nd method: Sand Consolidation

23. Prepacked
Screen
Chemical
Sand
Consolidation
External
Gravel
Pack
Internal
Gravel
Pack
Frac
and
Pack
Completion Types with Sand Control

24. • A sieve analysis is a laboratory routine performed on a formation sand
sample for the selection of the proper-sized gravel-pack sand.
• A sieve analysis consists of placing a formation sample at the top of a
series of screens that have progressively smaller mesh sizes downwards in
the sieve stack.
• After placing the sieve stack in a vibrating machine, the sand grains in the
sample will fall through the screens until encountering a screen through
which certain grain sizes cannot pass because the openings in the screen
are too small.
• By weighing the screens before and after sieving, the weight of formation
sample, retained by each size screen, can be determined.
• The cumulative weight percent of each sample retained can be plotted as a
comparison of screen mesh size on semi-log coordinates to obtain a sand
size-distribution plot
Sieve analysis for gravel pack selection

25. Schwartz sorting criteria
Uc < 3  uniform (well sorted) sand
3 < Uc ≤ 5  medium sand
Uc > 5  non uniform (poorly sorted) sand
Sorting Criteria:-
1. For formation sand having Uc < 5 & ev of sand < 0.05 ft/sec we select df(10) size
2. For formation sand having Uc < 5 & ev of sand > 0.05 ft/sec we select df(40) size
3. For formation sand having Uc > 10 & ev of sand > 0.1 ft/sec we select df(70) size
Diameter of gravel must be 6 times the diameter of the formation sand particles.
And for finding d90 size take Uc as 1.5

27. • Once the sieve analysis has been performed and plotted, the remainder of the
gravel-pack sizing can be performed graphically.
• With a straight edge, construct the gravel curve so that its uniformity coefficient,
Uc, is 1.5.
• The actual gravel size can be determined by the intercept of gravel curve with the
0 and 100 percentile values. Select to the nearest standard gravel size.

28. Sieve analysis
plot of a
disaggregated
formation
sand

29. Given the formation sand sieve analysis as shown in figure (in previous slide).
Determine median sand size & uniformity coefficient of sand: -
Also Select the proper gravel size (i.e. gravel diameter) for a well that is
expected to produce at a rate such that fluid velocity through half of open
screen area is about 0.02 m/sec: -
Use Schwartz gravel pack selection criteria and also mention the criteria.
SAND SORTING CRITERIA

32. The assortment of chemicals pumped down the well
during drilling and completion can often cause damage to
the surrounding formation by entering the reservoir rock
and blocking the pore throats (the channels in the rock
throughout which the reservoir fluids flow).
Similarly, the act of perforating can have a similar effect by
jetting debris into the perforation channels.
Both these situations reduce the permeability in the near
well bore area and so reduce the flow of fluids into the
well bore.
Let us remember …….