Lost Circulation Theory - Sd-ii_6405340_01.ppt

Lost Circulation

Objectives At the end of this module, you will be able to

Explain lost circulation

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Explain lost circulation consequences

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Classify the types of lost circulation

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Explain critical parameter in lost circulation

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Identify Lost circulation solutions

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Explain Lost Circulation Advisor

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Losses The total or partial loss of drilling / completion fluid or cement to highly permeable zones

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Loss of a highly complex balance between pore pressure, the hydrostatic/dynamic head and the frac/parting pressure

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Lost Circulation – A Costly Problem Time consuming Lost time due to slow drilling progress

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Poor cuttings removal (stuck pipe)

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Additional casing strings

Missing the target 

Damage to payzone resulting in skin

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Poor zonal isolation due to cement losses

Dangerous operation 

Kick/Blow out due to imbalance in the well

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Loss of well

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Loss Circulation in Different Operations

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Loss Mechanisms Lost Circulation

High Perm

Cavernous

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Induced Losses

Natural Losses

Natural Fractures

Induced Fractures

8

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Preventive Measures 

Minimize hydrostatic pressure

Determine the proper casing strings and casing points

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Drill with air, foam, or aerated mud

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Optimize mud properties

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Blind drilling ( mud cap or water)

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Maximize BHA clearance,

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Avoid the spudding of bridges

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Minimize swab and surge pressures

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Use inhibitive muds

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Pretreat the system

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Control the drilling rate

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Compile and maintain a database.

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Optimize solids control equipment

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Identifying the Loss Zone Occurs during drilling or is accompanied by a notable change in rotary torque, most likely on bottom. Indicates possible change in the formation such as a natural fracture, pore, vug, or cavern

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Happens while tripping in (including casing), wiping, or changing mud properties, most likely between bit or shoe depth and hole bottom. Indicates induced fracture, which can occur at any portion of the well.

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Repeat occurrence, previous loss zone reopened.

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Losses after an overpressured kick, above bottom.

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Logs can identify actual loss zone (temperature,spinner,tracer,GR)

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Critical Parameters for Treatment Design Severity of the losses Seepage

< 10 bbl / hr

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Partial

10 - 50 bbl / hr

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Severe

50 - 500 bbl / hr

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Total no returns

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Depth of the Losses 

at the bit

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below next casing shoe

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spread over OH section

Highly permeable and/or unconsolidated formation Cavernous or vugular formation Natural fractures and fissures Induced fractures

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Type of the Zone of Losses

Critical Parameters for Treatment Design (contd.) Formation damage 

With formation damage, acid or watersoluble solutions should be used in reservoirs

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With its high potassium content, mica can interfere with certain wireline logs

Durability 

temporary for short drilling or workover periods

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permanent for long-term operations

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low enough to allow proper penetration if required

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strong enough to seal and withstand differential pressures

Rig time 

as short as possible

Compressive strength 

sufficient to provide a positive seal

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Interference of logging

Gel strength

LCM Classification 

Granular - Kolite (D042), Gilsonite,Calcium Carbonate.

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Lamellar/Flakes

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Fibrous - Sawdust, Bark, CemNET* etc.

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- Cellophane flakes(D029), Polyester Flakes(D130), Mica

Loss Circulation Solutions While Drilling and Pre-Cementing Hole Section

Mud type

Solution

When

or

High perm/fissures and micro fractures

All

All

D097 Losseal* W/O in a pill or mud

< 40 bph

< 1 mm FW

Natural Fractures

NonWBM Reservoir

D199 Losseal* W in a pill or mud with optimized solids

> 40 bph

1 to 5 mm FW

Caverns and vugulars

All

All

ZONELOCK* S / ZONELOCK* SC

Severe to Total

-

All

All

All

PERMABLOK*

Severe to Total

-

InstanSeal / InstanSeal Cement

Severe to Total

-

Gunk Plug

When requested by customer

-

Cement Plugs (With CemNET*/ Cellophane Flakes/ Polyester Flake / KOLITE / RFC)

When requested by customer

-

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Problem

Loss Circulation Solutions (contd.) While Cementing, in the Spacer Hole Section

Mud type

Solution

When

Or

All

All

All

D199 Losseal* W

> 40 bph

1 to 5 mm FW

D097 Losseal* W/O

< 40 bph

< 1 mm FW

While Cementing, in the Cement Problem

Hole Section

Mud type

Solution

When

Or

All

All

All

D095 / D096 CemNET* LiteCRETE* Ultra LiteCRETE*

When losses are expected

-

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Problem

LCM Classification Sealing at the face of the formation

Sealing within the formation Schlumberger Private

CemNET* (D095/ D096) Advanced fibers mixed with cement to seal lost circulation

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Not recommended to treat losses while drilling by adding to drilling fluids.

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Engineered to an optimal size

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Inert – No effect on Thickening Time – No effect on compressive strength development – Compatible with all cementing additives

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Extremely effective with CemCRETE* systems – Better plugging effect due to PSD – Lower rheology

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CemNET* Applications  Preventing losses into fractures, fissures, vugular formations or high perm zones while cementing. Schlumberger Private

Preventing cement fall back after placement.  Providing a fibrous-net substrate to promote cement filter cake development.  Can be added to cement slurries for primary cementing or lost circulation plugs. Mixing  No dry blending  Fibers are post added to the slurry- either batch or continuous mixing in the tub 

CemNET* Chemical Code

Material

D095 (J501) Fibrous Glass

SG

Temperature Max conc. in Max conc. in ( deg C) conventional CemCRETE* slurries (lb/bbl) slurries (lb/bbl)

2.55 150

2.1 - 2.5*

2.1*

2.1*

*yard test is recommended before executing the job to avoid plugging of the pumping equipment Above concentrations are given in batch mixing mode.

Additives  J501, J502 if available can be used however, use only D095 and D096 labeled sacks 

Software can be downloaded to print D095 & D096 labels

http://wwwdsesgl.sugar-land.dowell.slb.com/Labels_International/Lbls_Setup.html

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D096 (J502) Fibrous Synthetic 1.27 232 Polymer

2.5 - 2.8*

Mechanism 

Dry fibers are bound together – Easy to handle and add to cement

No fiber lumps in mixing fluid

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Well dispersed fibers once agitated – High plugging efficiency – Water wetting effect by the surfactant

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Fibrous network across loss zones

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Mechanism

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Circulation

Fibrous network across lost circulation zones

Cellophane Flake (D029)   

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Laminated-type, lost-circulation additive of a controlled size Should be dry-blended into the cement at the bulk plant. Chemically inert- no appreciable effect on TT and CS Maximum concentration - 0.5 lbm/sk (mixing problems could result above this) Small quantities provide a large surface area for sealing off fractured and porous areas. Compatible with all commonly-used cement formulations.

Polyester Flake (D130)   

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Laminated-type, lost-circulation additive of a controlled size Should be dry-blended into the cement at the bulk plant. Chemically inert- no appreciable effect on TT and CS Maximum concentration - 0.5 lbm/sk (mixing problems could result above this) Small quantities provide a large surface area for sealing off fractured and porous areas. Compatible with all commonly-used cement formulations Similar to Cellophane Flake D029 but superior as it has a higher specific gravity and does not ”float out” of the cement slurry when batch mixing

KOLITE (D042) Loss circulation material as well as extender

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Angular shape of particles provides good bridging action at the face of the wellbore or within the formation effectiveness is due to the particle-size distribution which allows coarse and medium size particles to bridge. This forms a network that the finer particles of D042 and cement can seal. Lower slurry weight also helps lost circulation control because the hydrostatic pressure is reduced.

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Why is CemNET in mud not as efficient? Fluid Type

SVF 55% 44% 40%

Water extended 13 ppg slurry 13 ppg WBM

26% 17%

10 ppg WBM 9 ppg WBM

Low SVF

6% 2%

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LiteCRETE Regular 16.4 ppg Cement slurry Regular 15.8ppg Cement slurry

Losseal* WO (D097)  

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Typical % SVF for various fluid systems

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Fiber/Solid technology system for drilling fluids/ spacers (low SVF water or oil based fluids) Applicable for loss severity <40 bph Inert – Optimized ratio of  CemNET* Fiber  Mica flakes Can be used through drill bits, qualified BHA’s and float shoes with opening > 8 mm Base fluid (drilling fluid / cement spacer) should have Bingham model yield point of at least 10 lbf/100ft2 - 15 lbf/100ft2

The Solution: Concentration-

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–

Pill volume

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– – –

Previous experience or 1.5 times open hole volume of loss zone Minimum 20 bbls, recommended 40 bbls Depending on severity of losses, treatment might have to be repeated

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5 to 15 lbm/bbl depending on the SVF and the particle size of the weighting agent in the base fluid yard test to simulate the restriction in surface screens, mud motors, LWD, BHA screens, downhole tool or annular restrictions should be performed

Losseal WO Concentration

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Dispersion in Non-Aqueous Fluid (OBM/SBM)

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Losseal* W (D199)   

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Dual Fiber/Solid technology for losses to natural fractures Maximum fracture width – 5 mm Not designed for induced losses Can be used in spacer ahead of cementing or in a spotting pill during drilling Can be used through drill bits, qualified BHA’s, float shoes Can not be pumped through D&M PowerDrive due to the risk of plugging the screen in the bias unit

Losseal* W (D199) 

Composition Fiber type

Stiff fiber

Material

Nylon

Flexible fiber Polypropylene

Weight (%)

Color

90

Black

10

White

The base fluid (no solids and fibers) must have a Bingham yield point between 10 lbf/100ft2 and 15 lbf/100ft2  The pill must be designed with LCCA - Loss Circulation Control Advisor  Pill volume ( minimum 50 bbl) 

– Open hole volume capacity plus 50 % excess to anticipate the lack of information about loss zone. – Add 20 bbl to anticipate fluid loss during squeeze. – Add some volume to anticipate contamination and temperature uncertainty

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– Viscosifier ( D182+D020) – Blend of two fibers – Solid package( SVF > 25-40 %)

Mechanism

Refer to CMM Section14 for detailed placement procedure

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Four-step plugging mechanism –  Disperse - Fibers disperse easily in WB fluids  Bridge - Stiff fibers form a strong bridge  Plug - Optimized solid package with LCCA  Sustain - Flexible fibers allows resistance to erosion

BDO & BDOC (Gunk Plug) Mixture of bentonite, diesel oil ( also cement for BDOC)

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Makes contact with WBM downhole to make gel

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Pumped through drillstring with mud through annulus

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BDO preferred for partial losses and BDOC for total loss

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Similar concepts: – PDOC ( Plaster-Diesel Oil-Cement) - Plaster mixed with the cement to gel quick gelation – SOS – (Slurry Oil Squeeze) - Cement slurry prepared in oil without any bentonite – Polymer Plug – Bentonite and synthetic polymer mixed in oil

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ZONELOCK* S & ZONELOCK* SC

ZONELOCK SC*(D814) ( ZONELOCK S* followed by cement slurry)  Silicate pill rapidly dehydrates cement slurry upon contact creating flash set  “Hard Plug” lost circulation treatment that cannot be pumped through BHA  Applied for severe losses

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ZONELOCK S* (D813) (specialized Silicate solution)  Forms rapid semi rigid gel mechanism on contact with heavy Ca/Na brine’s  “Soft Plug” lost circulation treatment that can be spotted through any BHA  Silicate solution must NOT contact any chlorides until exit from stinger/BHA  Applied for small fissure losses or brine flow problems

PERMABLOK* Problems during drilling or prior to cementing; for permanently or in some cases temporarily plugging zones, and for consolidating weak formations.

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Temperature activated system based on downhole mixing

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Main Additives are: – D140 Low Temperature Hardener/ D141 ( High temp hardener) – D075 Sodium Silicate – S001 Calcium Chloride

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Max BHCT 130 deg C

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Working time for the gel depends on volume, BHT, rate of pumping

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PERMABLOK* Applications:

Lost circulation during drilling

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Expected losses during cementing

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Permanent plugging/squeezing of zones

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Zone consolidation

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PERMABLOK*

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InstanSeal* (D963) A lost circulation treatment that consists of a shear activated gel.

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Applicable for heavy mud losses

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Gel mechanism is triggered by pressure drop (>350 psi) during placement through bit nozzles. Shear breaks the emulsion and allows the cross-linker to pass from the oil phase to the water phase. In a few min, a crosslinked polymer gel structure of very high strength forms.

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Additives are: – Base Oil and water

– D172 Emulsifier, D171 Buffer, D170 Viscosifier – D020 Bentonite

P = 35 bar Water Phase containing high concentration of polymer Oil phase Cross-linker particle

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InstanSeal* Cement (D967) InstanSeal + cement

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Internal phase – water with high polymer concentration,

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Continuous phase - oil with polymer cross linker and cement

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Additives are: – Base Oil and water

– D172 Emulsifier, D171 Buffer, D170 Viscosifier – D020 Bentonite – Cement

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Regulated Fill-Up Cement (RFC*) 

RFC* slurries are highly thixotropic, forming a rigid gel shortly after slurry movement has stopped

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RFC* is a mixture of Portland cement and plaster • Expansion of cement while setting • Poor performance with low C3A content cements

– D111 – Liquid additive • No expansion on setting • Can be used with all Portland cements

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– D053 – Solid additive

Lightweight Cement Systems  Lightweight

 CemCRETE*

slurries

These can be combined with fibrous material like CemNET

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Cement Systems – Extended Systems – Bentonite, silicates – Lightweight Cements - TXI – Foamed Cement Slurries

PROTECTOZONE* Temporary, rigid aqueous gel systems used as zone-shielding agents

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Plugging Agent to appropriate volumes of fresh water or prepared sodium chloride (NaCl) brine. (Oilfield brine should not be used.)

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A water-soluble catalyst is added for control of setting times.

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Specific breakdown times are obtained by using a breaker.

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Breakdown times of one day to three weeks can be obtained

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Originally not designed for loss circulation but successful in cases where non damaging temporary solution is required

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