New dimensions in sand management

Screenless Sand Control Completions

Applications■ Primary sand control comple-

tion for new wells expectedto produce formation sand

■ Remedial sand control completion● for wells without gravel

packs that are producingsand

● for failed sand control completion with screens

● for wells with bypassed pay zones

Benefits■ Full wellbore access is

achieved for ● well logging● improved reservoir

management● easier future recompletion.

■ Overall well completion costcan be reduced through● less rig time being spent on

sand control completion ● elimination of operational

risks associated with downhole tools

● rigless through-tubing completion.

■ Formation damage caused by completion brine is significantly reduced.

■ By eliminating the use of a screen, no additional restriction exists in slimholesand control completions.

Features■ Integration of field-proven

techniques

■ Economics, risks and benefits analyses

■ Simultaneous stimulation and sand control

■ Optimized perforating

■ Near-wellbore chemical consolidation

■ Tip screenout (TSO) fracturing

■ Proppant flowback controlwith resin-coated proppant,PropNET* proppant-packadditive or a combination of both

Screenless completion—an alternativesand control techniqueScreenless completion is an alterna-tive method to conventional sandcontrol techniques. A comprehensiveapproach to managing sand inclusiveof enhanced risk assessment, screen-less completion methodology com-bined with field-proven techniquesoffers viable and effective strategiesto prevent sand production through-out the life of the well.

Problems associated with sand pro-duction can adversely affect reservoirproductivity and project profitability.If not properly addressed early, sandproblems can compound to the extentthat produced sand jeopardizes futurewell intervention options.

Applicable to both old- and new-wellcompletions, screenless completiontechnology is particularly useful in com-petent formations that can be consid-ered borderline on needing a gravelpack to prevent sand production.

Screenless completion employsexisting field-proven methods, result-ing in a fullbore completion withoutthe use of a screen and surrounding

gravel pack. Rather than using thebridging mechanism of a gravel packin the annulus between screen andcasing, formation sand is held backby a proppant pack with proppant-flowback-control additives insidethe hydraulic fracture.

By not having gravel-pack screens in the well, screenless completionoffers significant advantages to a con-ventional sand control completion,such as completion cost reduction,improved well conformance controland future flexible recompletionoptions. The screenless completion is an effective alternative method for controlling formation sand.

Fracturing for sand control The FracTROL* completion engineeringservice ensures present and future wellproductivity by combining certain tech-niques such as perforating, consolida-tion, fracturing and proppant flowbackcontrol. FracTROL techniques can beperformed without a rig, overcomingthe limitations of screened comple-tions and providing a cost-effectivemethod of sand control for both

Screenlesssand controlcompletion

Fracturing forsand control

Chemicalconsolidation

Perforating forsand control

Screenless sand control completions include three services—fracturing, chemical consolidation and perforating for sand control.

primary and remedial completions. By eliminating any skin associatedwith the gravel pack and screen, this technique also maintains full wellbore access to facilitate futurewell intervention.

Techniques include

■ optimized perforating, including orientation, size, shot density andinterval selection

■ consolidation to stabilize formationsand in wells with existing perforations

■ fracturing to stimulate production

■ proppant flowback control withresin-coated proppant, PropNETadditive or a combination of both

■ pinpoint placement of hydraulicfracturing using the CoilFRAC* service.

Critical perforating procedures

Perforating provides a means of com-munication between the wellbore andthe reservoir. In a fracture-stimulatedreservoir, the perforation is the conduit

between the fracture and the well-bore. In a cased hole completion, the perforation is the only avenuethrough which sand can be produced.Proper selection and execution of aperforating procedure is critical to thesuccessful FracTROL completion.

For FracTROL completions, orientedperforations should be shot perpen-dicular to the minimum principal stress;

i.e., aligned with the preferred fractureplane. General recommendations are

■ 180º or 0º phasing perforationsdepending on knowledge of formation stress distribution

■ the use of limited interval guide-lines and placement of perforations

■ shot density and charge type basedon the desired pressure drop ineither casing or cement.

FracturePerforationProppant packwith PropNET fibers

Proppant flowback control with PropNET additive, resin-coated proppant or a combination of bothkeeps the proppant in place. In turn, proppant placed inside the hydraulically induced fracture haltssand production.

Existing perforation

Gel consolidation

Fracturing throughconsolidated matrix

Remedial sand control completion for wells withoutgravel packs that are producing sand

The primary completion for new wells expected to produce formation sand

Step 1: Gel consolidation Step 2: Reperforating

Step 3: Fracturing

Step 1: Abandon lower zone

Step 3: Fracture new zone

Step 2: Perforate new zone

Remedial sand control completion for wells withbypassed pay zones

Remedial sand control completion for failed sandcontrol completion with screens

Gel consolidation prior to fracturing

If the FracTROL service is to be usedfor wells with existing perforations,these perforations need to be pluggedor consolidated to prevent sand pro-duction. If the cement is to be used toplug the well, then reperforating shouldbe performed prior to fracturing.

Consolidation, the process of bond-ing sand grains and formation fines, is also used to eliminate risks of sandproduction over time. Acid- and water-resistant bonds created between sandgrains exhibit a certain elasticityneeded to survive the fracture process.Placement of the gel must ensure cov-erage and consolidation of every openperforation.

Fracturing for effective treatment

Employing CoilFRAC and TSO fractur-ing services combines the benefits offracturing with the pinpoint placementof coiled tubing.

Coiled tubing conveyance and selective isolation

Conveyance by coiled tubing andselective isolation methods availablewith the CoilFRAC service make multizone treatment possible all in one trip. By selectively and accuratelyplacing proppant into each individualzone, the effects of varied stress andpressure are eliminated and volume is minimized. Multiple small treatmentscan be economically applied to maxi-mize reserves in layered sands and to allow flexibility in conformancecontrol.

TSO improved fracture conductivity

TSO fracturing is recognized as themost important tool for ensuring ade-quate fracture conductivity in high-permeability formations. In a high-permeability formation, one way to achieve an acceptable fracture flowis to substantially increase the fracturewidth. To increase width, the fractureis screened out at its tip and subse-quently inflated. The development of

cleaner nonpolymer fluids, such as theSchlumberger ClearFRAC* fluid, hasalso contributed to significantlyimproved fracture conductivity values.

Reliable proppant flowback controlis essential for a successful FracTROLcompletion. Currently, PropNET addi-tive and resin-coated proppant arebeing used to prevent proppant flow-back. PropNET additives are fibersthat are intimately mixed with slurryand pumped into the well to keep theproppant in the fracture by means of a physical reinforcement mechanism.Proppant placed inside the hydrauli-cally induced fracture halts sand production.

Successfully employed in more than4000 treatments, PropNET additivedoes not require any shut-in time andis effective in reservoirs with tempera-tures to 400ºF. Depending on bottom-hole temperature, desired chemicalresistance, expected fluid velocities inthe fracture and desired proppant-packpermeability, various materials andsizes of PropNET fibers are selected.

Retain permeability through chemical consolidationWhere fracturing is not possible, twoconventional chemical consolidationsystems are available to prevent themigration of formation sand and otherfines to the wellbore—the K300 andSANDLOCK* V systems. The K300furan resin system is used for in-situformation consolidation, whereas the resin-coated SANDLOCK V tech-nique is used for gravel packing theformation.

K300 resin system—bonding of sand particles

Resin system technology is based onpolymerization reactions of resininjected into loose or unconsolidatedformations in the near-wellbore matrix.The resin cures to a hard plastic thatbonds sand and fines particles togetherso that they cannot migrate to thewellbore.

Once in place, the K300 resin helpsprevent the migration of other loosesand and fines, offering higher retainedpermeability and better compressivestrength than standard resin consolida-tion systems. Lower in initial cost andenvironmentally friendly, the K300resin yields higher production rates.

The K300 system can be used toconsolidate the formation before per-forming a fracturing treatment. Sandproduction from the perforations isprevented by the proppant pack usingproppant-flowback-control technology.Perforations not in communicationwith the fracture are protected by the resin.

Used after perforating, this viscosity-controlled system works by “smooth-ing” the injection profile in water injection wells drilled in formations of varying permeability.

SANDLOCK V service—creating an artificialsandstone network

This resin-coated gravel-packing tech-nique places a strong but highly per-meable artificial sandstone gravel packin perforation tunnels and outside thecasing to prevent the migration of for-mation material into the wellbore.

A high-density resin-coated slurry isprepared in a thickened brine-carryingfluid and is pumped down the work-string through the perforation tunnelsuntil a screenout is obtained. After theresin cures, the consolidated gravelpack in the casing is drilled out or a pilot hole is drilled through the sand pack, and the well is returned to production.

Resistant to deterioration by pro-duced fluids and most treating chemi-cals, the SANDLOCK V resin-coated

gravel requires less rig time as a resultof the rapidly setting resin and thinningof the viscous carrier gel after place-ment. Well cleanup time is shortenedand formation damage is lessenedbecause a relatively small volume offluid is used to place a large-volume gravel network.

Particularly suited for remedial sandcontrol and for repairing damagedscreens, the SANDLOCK V service isalso effective in primary completionsand injection wells. The slurry issqueezed into the perforations andagainst the formation. Once cured, theslurry forms a set network with a com-pressive strength of approximately3000 psi and a permeability of 100 Dwith 20/40 mesh gravel.

A K300 resin job is being prepared on location prior to injection into the well.

Perforating solutions to manage sandThe tendency for a well to producesand along with oil, water and gasdepends on numerous factors such as formation strength, perforationstresses, flow rate and fluid type.

Perforation tunnel stability deter-mines whether sand production will be a concern in a completed well. Per-foration tunnel collapse or formationfailure between perforations causessand production in weak consolidatedformations. Optimized perforatingtechniques, based on enhanced riskassessment, can delay or avoid sandproduction over a well’s productive life.

As one of the screenless completionmethods, optimized perforating canhelp prevent production of sand fromwithin the formation.

Choosing conventional sand control or sand-prevention perforating

Perforation and formation stability and the ability to accurately predictthem influence whether conventionalsand control or screenless sandcontrol strategies should be under-taken. Weak but consolidated forma-tions that support a perforation tunnel

are good candidates for perforatingsand control techniques (formationsthat are too weak to support a perfora-tion tunnel are unlikely candidates).Sand production in more competentformations generally arises from either tunnel collapse or loose sand in the tunnel.

When risk of sand production isdetermined to be acceptably low,screenless prevention techniques areoptimal. When the risk is unacceptablyhigh, conventional sand control meth-ods are the preferred course.

Optimal use of screenless perforating technology

Schlumberger perforating techniquesfor sand control create more stableperforation tunnels in the formation,optimizing the hole size, penetrationand perforation-to-perforation spacingfor a given pressure drawdown acrossperforated intervals and flow rate per perforation. Underbalanced perfo-rating enables loose perforation sandto be produced early, which helpsavoid impaired productivity and sand issues during the later stages of a well’s life.

Upgrading perforating performanceinvolves optimizing parameters suchas charge type, shot density, phaseangle and, in some cases, orientation.

Charge type

Optimized shaped charges offer controlled hole size and penetration:

■ Deep penetrating charges are usedto enhance single-perforation stabil-ity during drawdown and depletion.They also, along with optimum perforation spacing, enhance thestability of the adjacent formation.

■ Optimized charges are used toenhance hydraulic fracturing treatments.

Shot density

Higher shot densities increase the area open to flow, keeping pressuredrawdown, flow rate and drag forcesthrough each perforation below a critical value.

Phase angle

Optimizing the phase angle for a givenwellbore radius and shot density maxi-mizes the perforation-to-perforationspacing, which in turn decreases oravoids interaction between adjacentperforations and the surrounding rock.

Perforation orientation

Selective and/or oriented perforating is used to place the perforations awayfrom less stable sectors in the forma-tion (e.g., orientations) that have largecontrasts between horizontal and vertical stresses.

0° 300° 360°240°180°120°60°

L1

L2

L3

An optimized phase angle maximizes the spacing of perforations, which lessens or eliminates the interaction between the perforations and the rock.

Case historiesMillion-dollar savings on cleanup

In a recent application of completiontechnology, a well was refracturedusing a combination of resin-coatedproppant and PropNET additive tocontrol proppant flowback. After thesuccessful TSO fracturing stimulation,sand-free production was achievedand a savings in cleanup costs was realized.

The 4-month-old well had been pre-viously fractured using a competitorproduct. Because the well was pro-ducing solids exceeding permissiblelevels to bring on production, sandcontrol coupled with a restimulationeffort was warranted. Schlumbergerperformed a restimulation treatmentusing the screenless completion tech-nique. The interval had been perforatedusing oriented perforating techniqueswith limited interval guidelines forscreenless completions.

To ensure success of proppant flow-back control, 1.2% PropNET Goldadditive was used in combination with16 to 20 resin-coated proppant duringthe fracturing job. The treatment wasperformed successfully without clean-up problems and solids productionceased immediately after cleanup.

Back in production within a week,the well tested at over 30 MMscf/D at a savings of more than $1.2 millionover typical cleanup costs.

Screenless techniques successful in horizontal wells

Early gravel-pack and perforatedcompletions had failed in the weakchalk formations of the Valhall field.Following an engineering study, a screenless completion treatmentinside cased horizontal wells was performed with excellent results.Since then, more than 100 successfultreatments have been placed.

Between three and seven fracturingtreatments have been performed ineach horizontal well. A 5-ft intervalwas perforated with 180º phased per-forations. A TSO fracture was placed,inclusive of proppant flowback control,to keep the proppant in the fracture.

Post-treatment data show an aver-age sand-free production increase of 1000 to 3000 BOPD per fracturewith an even inflow profile along the horizontal wellbore.

Increased production in heavy-oil steamflood environment

Fourteen zones in four wells werecompleted in high-permeability heavy-oil steamflood environments. Intervalsup to 24 ft in length in vertical wellswere perforated with 0º phasing perfo-rations. The wells were subsequentlyfractured following screenless comple-tion guidelines and using the CoilFRACtechnique. These wells are producingsand free at rates 250 to 350 percenthigher than rates in offset wells.

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screenless completionAfter

screenless completion

Cleanupdays

A restimulation treatment using PropNET Gold additive in an interval perforated using Schlumbergeroriented perforating techniques and interval guidelines for a successful completion resulted in signifi-cantly reduced cleanup costs. PropNET treatment reduces average cleanup time from 47 to 6 days.

TSL-2724 ©Schlumberger

December 2001 *Mark of Schlumberger

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