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Sand ControlFundamentals & Design

D. Koukhani / A. Hooshmand

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HOW SANDING OCCURS

In most sandstone reservoirs sanding occurs in two stages:

• First, the rock fails mechanically in the near wellbore area because of changes in and redistribution of the stresses as the bore is drilled or produced. Mechanical failure does not necessarily mean immediate sand production.

• Then after the rock has failed, viscous drag forces generated by the flow of production fluids erode the failed material into the wellbore and up the flow path to surface.

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Main Geological Characteristics of Sandstone Reservoirs

Sandstone minerals can be split into three main groups:

• Detrital residue• Secondary detrital residue • Chemical precipitates

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Sandstone minerals:• Detrital residue:

Contain minerals from a source rock that have been transported and deposited mechanically, with quartz and feldspar typical of this group.

Main Geological Characteristics of Sandstone Reservoirs

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Sandstone minerals:• Detrital residue• Secondary detrital residue:

Clays are representative of secondary detrital minerals that have also been transported and deposited mechanically.

Main Geological Characteristics of Sandstone Reservoirs

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Sandstone minerals:• Detrital residue• Secondary detrital residue • Chemical precipitates:

Minerals deposited from solution by chemical or biochemical processes.

Main Geological Characteristics of Sandstone Reservoirs

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1. Quartz: Concentration range of 50 – 70% can form up to 99% of the rock.2. Feldspar: Concentrations of up to 12%, the next most common sandstone minerals after quartz.3. Heavy mineral4. Cementing material5. Other

Main Geological Characteristics of Sandstone Reservoirs

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Formation of Sandstones

Sandstones, like all sedimentary rocks are produced by a combination of

• Weathering of existing rocks (igneous, metamorphic and sedimentary-older sedimentary).

• Transport and erosion of the weathered material and diagenesis.

Weathering results in the breakdown of the existing rock into smaller particles. These are then moved by wind, water, gravity or a combination of the three.

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Classification of Sandstones

Sandstones have been classified by various criteria such as particle size or shape, sorting, mineralogy of the grains or of the cementations material etc.

One common method uses the following classification by mineral content:• Arkoses• Greensands• Greywackes

Sandstones are also classified by their grain size: • Coarse Grained Sandstone.

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Wentworth scale is used to measure grain size:

Particle Size Measurement

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Methods:There are two common methods used for determining the particle size distribution of a sedimentary rock:

• Sieving• Laser Diffraction

Particle Size Measurement

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SievingAdvantages:• Cheap & UsableKey Disadvantages:• Not possible to measure sprays or emulsions• Measurement for dry powders under 38 microns very difficult • Clays difficult to measure• Not high resolution• Particles not very well dispersed• Needs at least 20g• Does not measure below 45 microns

Particle Size Measurement

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Laser DiffractionAdvantages:• Flexibility• Dry powders can be measured directly• Liquid suspensions and emulsions can be measured• Entire sample is measured• Quicker than sieving• Sample size depends on particle size but typically <1g• Measures average diameter of particles• High resolutionKey Disadvantages:• Equipment is expensive – specialist test facilities required.

Particle Size Measurement

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Comparison between LDS & Sieve Analysis

The four main parameters utilized from the grain size distribution analysis are D10, D40, D50 and D90.

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Sampling Methods

There are two fundamental methods of sampling sandstone reservoirs – downhole coring and surface sampling. These can be subdivided into:• Rotary coring• Sidewall coring• Bailing• Surface sampling of circulated or produced material

Samples can be obtained from:• Cores• Drill Cuttings• Junk Baskets

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Sand Face Completion

The choice of equipment which is run across the formation interval forms the sand face completion.

The selection will be based on whether the well is• Open hole or cased and perforated,• Vertical, deviated or horizontal, and• Expected production conditions

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Choices of completions for sand control across the formation face:

• Screens• Frac-Pack• Gravel Pack• ESS / CHESS• Slotted Liner• Chemical Considerations

Sand Face Completion

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Screens

Different types of screens that use a different filtering media exists: • Wire-wrapped screensHave a base pipe with slots or holes around the circumference that is either single-wire wrapped or surrounded by cylindrical sieves of various mesh sizes.

• Pre-packed screensEmploy a different filtering media. A layer of consolidated resin coated gravel is placed around the internal screen assembly and is supported by a shroud or external screen.

• Premium screensPremium screens are typically an all-metal design, with a metal mesh filtration media and a protective outer metal shroud.

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Wire Wrapped Screen

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Pre-Packed Screen

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Premium Screen

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Frac-Pack

• Frac-pack is a sand control method by which a propped hydraulic fracture of limited length is created into a weak or unconsolidated reservoir.

• Wells producing from unconsolidated reservoirs using frac-packs require lower drawdown pressures to produce.

• The main reasons for using frac-packing as a sand control technique are: – By passing formation damage– Reduce water coning– Controlling sand production– Enhance productivity in low permeability formations

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Gravel Pack

In a gravel pack, the annulus between the wellbore and a base perforated pipe with wirewrapped screen, is filled with gravel.Advantages

• Productivity impairment can be minimized by design

• Especially useful for heterogenous sands in long productive intervals

Disadvantages

• Complicated workovers

• Chemical compatibility of WBM and produced fluids

• Risk of incomplete gravel pack leading to premature screen failure

• Screen damage from erosion and corrosion is a major concern

• Chemical compatibility of OBM and carrier fluid

• Can be difficult to use in deviated and horizontal wells

• Flow control and isolation is complex

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Expandable Sand Screen (ESS)

• Unique approach to solve sand control problems.• Large OD expanded to contact the wellbore stabilizes

formation.• System designed to resist erosion and plugging.• Large ID to maximize well intervention options.• Large and uniform flow area to optimize production.• Simple deployment minimizes operations costs.

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Slotted Liner

• tubing sections with a series of slots cut through the walls in an axial orientation.

• The main limitation of slotted liners is their flow area – an average of 3% and maximum of 6% is accepted.

• Flow areas of more than 6% are detrimental to the tensile strength of the pipe.

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Slotted LinerCommon Slot Profiles

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Chemical Considerations

• Used in formations with little or no cementitious material.

• A major benefit is that the wellbore is left free of obstructions.

• Fundamental principle =

bond the quartz grains together using a liquid resin.

• This will then provide an artificial cementing material between the grains.

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Expandable Sand Screens (ESS) Design & Construction

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Slots open upOuter ShroudEST Base Pipe

Slots open upWoven FilterSheets slides over one another

ESS Design

1 2 3

UNEXPANDED

EXPANDED

Expandable Base Pipe

Expandable Outer Protective Shroud

Overlapping Layers of Filter Media

No change in weave aperture

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3 LAYERS SANDWICHED TOGETHER

Outer Shroud

EST Base PipePetroweave

1 2

3

ESS Manufacture

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The ACE Tool is runafter the fix cone forBorehole contact .

1800 psi hydraulic actuation

Compliant Expansion speed 10ft/min

Axial Compliant Expansion Tool

Axial Compliant Expansion Tool

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Compliant Expansion Benefits

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Total Production = 10,500 bpd

Total Production = 15,700 bpd

Increase with ESS Screens = 5,200 bpd =$208,000/day!!!

Value of ESS - NISOC

Well # WHP (psi) Rate (BBL/D) Choke Salt (gr/m3) Sand ProblemAZ-156 1312 4,000 36/64 11 NOAZ-149 1210 3,000 34/64 19 NOAZ-91 1300 2,000 28/64 11 NOMI-42 850 3,200 32/64 11 NOMI-12 890 3,500 36/64 11 NO

Well Performance after Re-Completion with ESS

Well # WHP (psi) Rate (BBL/D) Choke Salt (gr/m3)AZ-156 1220 2,500 32/64 11AZ-149 1060 1,500 24/64 11AZ-91 1300 2,000 28/64 11MI-42 850 1,500 24/64 11MI-12 910 3,000 32/64 11

Well Performance with IGP

Project costs (excluding workover) recovered in 5 days