Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors Quartz School For Well Site Supervisors

Quartz School for Well Site Supervisors Module – 7 Well Cementing Ops.

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Section – 3 Well Cementing – III

Day 3

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Well Cementing

Agenda • Review Day 2 and Homework

• Evaluation of Cement Jobs • New Technology

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• IPM Cementing Standards

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IPM Cementing Standards

Cement Placement Procedure IPMIPM-PRPR-WCIWCI-005

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• Slurry and displacement volume calculations must be carried out independently by at least two competent personnel. • Agreement on the calculated volumes must be obtained prior to the cementing operation. • The amount of over displacement volume if a plug bumping pressure fails to be observed needs to be clearly agreed upon and communicated to all concerned at this stage. • For openhole intervals, the use of an integrated 4-arm caliper is recommended. Where no caliper measurement is available, an excess volume based on the experience in the area will be applied to the openhole interval, or a fluid caliper method will be used to measure the hydraulic diameter of the hole. A minimum of 10% excess should be run on all primary cement jobs, or as required by local government regulations. • When the rig pumps are used for cement displacement, their volumetric efficiency must be checked prior to the cement job to ensure accurate placement. Duplex pumps, or pumps with non-charged suctions should not be used for cement displacement. Displacement using the cement unit is not preferential for mud displacements with high weight, foaming tendencies, or aeration, as systematic errors tend to be magnified by the displacement tank volumes. • To minimize the chance of formation breakdown, the cement displacement rate should be kept below the maximum circulation rates at which no losses occur. As part of the cement job design, the calculated equivalent circulating density–ECD–should have been compared to the equivalent mud weight–EMW–of the leak-off test value for the previous casing shoe or at the weakest known point of the open hole.

Cement Placement Procedure IPMIPM-PRPR-WCIWCI-005

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• Throughout the cement job, the returns from the annulus should be monitored. All losses occurring after the cement has been pumped in to the annulus should be considered to be cement losses. • A float shoe and float collar should always be used. • If the casing is pressure tested immediately after bumping the plug, ensure that the resulting burst and axial loads have been taken into account as stated in the Green Cement Pressure Test load case of the Casing and Tubing Design Standard IPM-ST-WCI-025. • If the casing is not pressure tested immediately after plug has been bumped, sufficient cement thickening time should be allowed prior to pressure testing of the casing to prevent the formation of a micro-annulus. • Ensure that the resulting burst and axial loads have been taken into account as stated in the Pressure Test load case of the Casing and Tubing Design Standard IPM-ST-WCI-025. • The maximum over displacement (over the calculated theoretical volume) should be one half of the shoe track volume. • Efforts will be made to avoid contamination or channeling of the cement slurry. The hole should be circulated clean prior to the cement job. • Gel strengths of the mud system should be reduced to maximize mud mobility. • For liner cementing, the returns during the circulation with the liner landing string after the cement job will be carefully observed in order to assess the presence of spacer fluids and cement slurry above the top of liner.

Cement Placement Procedure IPMIPM-PRPR-WCIWCI-005

All liners- The integrity of the liner lap seal must be confirmed (pressure test, inflow test).

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• All casing strings should be reciprocated and/or rotated during cement jobs wherever possible. Pipe is to be reciprocated to a maximum load of 75% of the rating of weakest string member, or 85% of the rating of hoisting equipment and derrick. If pipe rotation is used, the maximum makeup torque of the top joint should not be exceeded. • On semi-submersibles, drillships or where other critical space-out applications are required, reciprocation while circulating, and mixing until cement is in proximity to the shoe may be considered. • It is recognized that the decision to stop or forego reciprocation must be a local decision after careful assessment of the relative risks and benefits. • It is required as a minimum to determine the top of cement for all casing and liner jobs using the following methods: All casings- The volumes pumped, volume returned, and the differential pressure must be measured and recorded. Where no returns are made to surface, subsea mud returns should be monitored and reported. On land operations where measurements of returns are more difficult, it is recommended to constantly monitor the fluid returns during cementing and displacement.

Setting and Verification of Plugs IPMIPM-PRPR-WCIWCI-006

• The cement should be batch mixed where possible, to ensure homogeneity. • As contamination of the cement plug with mud is the main reason for plug failure, a spacer should be used ahead of and behind the cement (spacer weight to be between the mud and cement slurry weights). The respective spacer volumes (ahead of and behind the cement) should be calculated so that the hydrostatic pressure balance is not affected. 5.2 Use of a Diverter Sub and Stinger • The use of a diverter sub or perforated stinger should be considered to minimize the chances of cement contamination and sinking of the plug, as the common practice of using open-ended drillpipe is a major contributor to plug failure. • If the workstring in the hole is 4 1/2” or larger, a tailpipe of lesser diameter (2 7/8” or 3 1/2” tubing stinger), and preferably with small upset tool joints, should be used to minimize disturbance on pulling out. 8

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5.1 Plug Setting Method • All plugs will be set using the balanced plug method (also called the balanced method). In this method, the hydrostatic pressure in the annulus and in the drillpipe/stinger are equal at the time of placement (in practice, it its recommended to slightly under displace, especially for holes with small annuli. This also allows the pipe to be pulled “dry”). The use of cementing aids such as the U-tubing control tool or the plug placement tool should be considered to reduce contamination and to increase control in setting the plug.

Setting and Verification of Plugs IPMIPM-PRPR-WCIWCI-006 5.2 Use of a Diverter Sub and Stinger • The length of the tailpipe should always exceed that of the cement plug (recommended is 1.5 times). Consideration will be given to centralization of the tail pipe. The drillpipe may be rotated during cement placement but avoided thereafter until the pipe is pulled above the plug. In addition, the pipe should be pulled very slowly when pulling it back above the cement. • For off-bottom plugs that are unsupported by a bridgeplug or similar, the placement of the plug may be uncertain: • Consider spotting viscous pill (viscous mud or bentonite pill) below the cement plug’s planned depth in any of the following situations: • The density differential between the mud and cement is substantial (say more than 2 ppg) • The hole is deviated • The hole size is large The pill will minimize the chance of the cement sinking by gravity. The weight of the viscous pill should be the same as the mud weight.

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5.3 OffOff-Bottom Plugs

Setting and Verification of Plugs IPMIPM-PRPR-WCIWCI-006

5.5 Circulating above the Plug • After pulling the pipe to the theoretical top of cement, the excess is normally circulated out. This is done by reverse circulating for a cased-hole plug, but reverse circulation for openhole plugs should only be considered after careful evaluation of ECD (Equivalent Circulating Density) because losses may be initiated by the high back pressures. If ECD is critical, or if losses have been experienced when setting the plug, no reverse circulation should take place.

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5.4 Kickoff Plug Considerations • For kickoff plugs, a sharp contrast between the plug and the formation hardness is required. To achieve this contrast, the plug must exhibit high compressive strength. A minimum compressive strength of 5000 psi is required, while a 7000 psi compressive strength is preferred. For kickoff plugs, allow ample time for the cement to set (24 hours).

Setting and Verification of Plugs IPMIPM-PRPR-WCIWCI-006 5.6 Tagging Plugs • All openhole plugs intended to isolate two zones of different ages, significantly different pressures, or significantly different contents should be verified by tagging and weight testing after surface samples are hard.

• Cased hole plugs that are not supported by a verified bridgeplug or similar device should be verified by pressure testing to a pressure that is above the differential leakoff value below the plug(1), and / or by tagging and weight testing using a minimum of 20,000 lbs. All kick-off/sidetrack plugs should be weight tested with a bit (open nozzles, WOB: 15 to 20,000 lbs minimum, with the rig pumps on). The hole should be circulated clean after dressing the plug, prior to pulling out of hole. (1) Do not exceed 80 percent of the burst rating of the casing

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• If a series of plugs is being set across one interval or several intervals that do not vary widely in age, pressure, or contents then it is only necessary to tag and weight test the last plug.

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Cement Job Evaluation

Evaluation of Cement jobs A cement quality can be measured by:

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CBL/VDL Logging after cement has set around casing. Pressure testing the shoe during an LOT. Inflow testing of Liner Laps. Pressure testing against drilled out squeezes. Pressure testing on top of cement plugs. Setting down weight on cement plugs.

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• • • • • •

Cement Evaluation Methods • Hydraulic testing • Acoustic – Sonic (CBL/VDL, CBT): omnidirectional – Ultrasonic (USI): high resolution image

• Analysis of cement job data – Job Signature

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• Temperature, nuclear (cement top)

Sonic fundamentals • The transmitter sends an omnidirectional pulse

• Part of the wave front, refracted straight down the casing, is used to determine Amplitude and Transit time. time

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T

3’ R 5’ R

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• The “compression” waves travel through casing and are first to reach the 3-ft receiver.

Sonic fundamentals - CBL

No No Cement Cement

Tx

Rx

Cement Casing

Good Good Bond Bond

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Tx

Rx

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• When the casing is bonded to hard cement, the vibrations in the casing are attenuated or mud proportionally to the bonded surface area.Water Casing

Sonic fundamentals - VDL • Variable Density Log is the full wave display of the 5-ft receiver.

• To allow easy differentiation between casing and formation signal.

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Mud

time usec

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• Contrast depends on positive or negative amplitude.

Casing Formation

Amplitude (mv)

• Displayed as light and dark stripes.

Transmitter firing

Sonic fundamentals - VDL • Unless casing is fully eccentric the presence of formation arrivals is: A qualitative indicator of the presence of a solid material behind the casing

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By no means a quantitative indicator of its presence

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Example of a good CBL • Check quality – Look at TT curve

Example of a SALTBOND slurry 7-in. liner 19

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• Check CBL curve – Relatively low amplitude • Verify VDL – No casing arrivals – Formation arrivals

Example of a “bad” CBL • Check quality – Look at TT curve

Example from a 9 5/8-in. casing 20

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• Check CBL curve – Relatively high amplitude • Verify VDL – Casing arrivals – Weak formation arrivals • Isolation???

CBL Amplitude for a perfect cement job (1) • Basic interpretation: – Low measured amplitude: good cement no cement

• Drawback: too simplistic (examples of 100% bond amplitudes)

Casing/Cement 3 MRayl 6 MRayl 5 ½in. 17 lb/ft 6.1 mV 1.0 mV 9 5/8 in. 47 lb/ft 12.2 mV 3.3 mV Logging fluid: 9.0 lb/gal water base mud 21

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– High measured amplitude:

CBL Amplitude for a perfect cement job (2)

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3.5 MRayl 12 mV 100% bond

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CBL / VDL

5.5 MRayl 2 mV 100% bond

CBL Amplitude for a perfect cement job (3) • CBL amplitude depends on: – Logging fluid acoustic properties – Cement acoustic impedance (not compressive strength) •

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Cement acoustic impedance can either be measured or predicted

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– Casing size and weight

Acoustic Impedance Materials

Heavy

6 Z MRayl

Setting slurry

4 Light

Heavy mud

2 Water Oil

0 24

Neat Cement

Gas

Liquid

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• Acoustic tools respond to acoustic impedance (acoustic hardness) Z • Z = density x acoustic velocity • Z is expressed in MRayl (106 kg.m-2.s-1)

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Example of CBL Adviser output ft 0.0

3.0

Mrayl 4.5 6.0

4.0

8.0

12.0

CBL (80% ) CBL (100% )

Concentric casing

0.0

800.0

OD 9 5/8 in @ 500f t

LC @ 920 f t

1200.0

OD 7. in @ 1000f t

W ell 25

Fill

Impedance

C B L A mplitude

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400.0

Impedanc e

mV 7.5

UltraS Sonic I mager Principle

Free pipe

Good cement

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The USI evaluates cement with • An ultrasonic transducer (0.2-0.7 MHz) • The resonance technique

Ultrasonics (USI) advantages over sonics (CBL)

– Detailed picture of material distribution: solid, liquid, gas, debonded cement – Detects narrow channels

• Easier interpretation and less uncertainty than sonics (CBL/CBT) • Casing inspection in same pass 27

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• Tolerates liquid (wet) microannulus • Full coverage, 30 mm resolution image

The USI view Gas microannulus

Casing weld Mud channel

Well centered casing Eccentered casing Washout

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Perfs

UltraS Sonic I mager • Ultrasonic tool operating between 200 and 700 kHz.

• Measurements • Cement evaluation • Casing corrosion and wear 29

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• Full casing coverage at 1.2 in. (30 mm) resolution using rotating transducer

USI Measurements

(Internal casing condition)

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Transit time Internal radius

Thickness

Cement Impedance

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Echo amplitude

USI cement image settings The USI discriminates between solid, liquid and gas/dry microannulus using acoustic impedance thresholds. 8 Light

Z MRayl

Standar d

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Interpreted Image

Cement

Maximum impedance

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Solid/liquid threshold ZTCM

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0 31

+/- 0.5

Liquid Gas/liquid threshold Gas or dry micro-annulus

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Raw image

USI combined casing + cement presentation QC

Casing

Cement

Channel Schlumberger Private

Bond index Cement raw Thickness Thickness Internal radius Cement Casing cross-section interpreted Amplitude Processing flags Process flags, Eccentering, CCL, gamma 32

USI + CBL/VDL cement presentation QC

CBL

USI

VDL

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CBL

VDL Bond index Acoustic impedance Cement image interpreted CBL, gamma Process flags, eccentering 33

USI and CBL/VDL

– Contaminated cement – Wet microannulus – Dry microannulus

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• In simple cases (good well-bonded cement, free pipe, mud channel) the tools agree. • In more complicated real-life situations the tools have different responses which can aid interpretation:

Good cement CBL flat, low

Strong formation arrival

Mean Z 8 MRayl

Weak casing arrival Schlumberger Private

QC

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CBL

USI

VDL

Mud channel and contaminated cement Weak formation arrival CBL variable, high

Strong casing arrival Schlumberger Private

Channel Low-Z cement

QC

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CBL

USI

VDL

CemCADE Job Signature

– eliminate guesswork – well’s unknown factors

• The Concept of Job Signature – Begin-End of U-Tube, slopes of curve – verify well control during cement job – confirms unnoticed losses 37

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• Validated simulator • Verify validity of design parameters

Evaluation • Re-run CemCADE with the execution data:

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– Placement – U-Tube effect – WellClean II – Synthetic CBL

Losses during displacement •

• •

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Losses during displacement confirmed by CemCADE playback Low TOC Displacement rate to be reduced when pressure drop observed

Density Control during Slurry Mixing Slurry Volume

0.6937 1.404 0.63%

Volume Each Class

Evaluation of density control during mixing/pumping cement slurry: – To ensure slurry stability – To ensure slurry properties as per design

2.5789 1.464 2.35%

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50.00%

45.00%

40.00%

35.00%

30.00%

25.00%

20.00%

15.00%

10.00%

5.00%

0.00% 1.404

1.416

1.428

1.44 De ns ity

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1.9158 1.476 1.74%

Lead Slurry Volume Distribution

Volume %

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% each Class

109.86 3.0392 30.493 54.271 16.831 1.416 1.428 1.44 1.452 2.77% 27.76% 49.40% 15.32% 92.48%

1.452

1.464

1.476

Synthetic CBL •

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Based on playback WELLCLEAN data Synthetic CBL is predicting % of bonded cement to the casing

Evaluation of Cement jobs Other Methods • Pressure testing the shoe during an LOT. - This can show a poor cement job at the shoe as well as the leak off pressure to the formation. - When a liner is cemented across a production zone, Inflow testing or a Negative test can be done when the hydrostatic of the displacement fluid is less than that of the original mud and liner cement. The open casing is observed at surface for flow back and/or bubbles.

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Pressure testing against drilled out squeezes or plugs - A simple pressure test against the top of a plug or squeezed perforations will indicate if all leak paths have been effectively sealed.

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• Inflow testing of Liner Laps.

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New Technology

New Technology • CemCRETE

• CemNET • CemSTREAK • SFM (Solids Fraction Monitor) 44

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• CemSTONE

Conventional Cement Slurries Cement particles must be surrounded by water to flow as a slurry

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Sufficient water must first be added to fill the void between the cement grains

Conventional Cement Slurries (Cont.) but you also have:

• lower density • lower viscosity

• longer working time • lower compressive strength • higher permeability

Good slurry properties≠ Good mechanical properties

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With more water you have:

CemCRETE (Cont.)

• PVF depends on shape and size of the particles

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• Created by increasing the Packing Volume Fraction in the powder

CemCRETE (Cont.) What makes PVF innovative?

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• PVF uses physics instead of chemistry • It disconnects water content from rheology • The slurry and set cement properties result from the dry blend not the water content

CemCRETE (Cont.)

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• Three class systems with centered PSD • A class can be one or more components of a given size

CemCRETE (Cont.) Less water = improved mechanical properties

Normal Portland

2

59% porosity @ 15.8 lb/gal

40% porosity @ 9 - 25 lb/gal

CemCRETE

0

77% porosity @ 12.5 lb/gal

4

6

8

10

Mix water needed (gal/sk) 50

12

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Conventional lightweight

Conventional cement properties vs. CemCRETE technology 160 0.2

Fluid Loss (mL)

140

Permeability (mD)

0.18

120 0.16 0.14

100

0.12

80

0.1

60

0.08

70

0.04 0.02 0

Lightweight

Conventional

40

60

20

50

0

Lightweight

40

Conventional

30 20

4000

10

24 hr Compressive Strength (psi)

3500

0

Lightweight

3000

Conventional

40

Acid Solubility (wt %)

35

2500

CemCRETE 30

2000 1500

25

1000

20

500 0

Lightweight

Conventional

Conventional cements

15 10 5 0

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Lightweight

Conventional

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Solid Fraction (%)

0.06

CemCRETE Technology

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• Production cements are lighter. • High-density cements have greater versatility • Cold-water cements set faster. • Remedial cements inject better.

At any slurry density 52

LiteCRETE LiteCRETE slurries can change the way you think of cement Cement slurries with density lower than water Fast Compressive Development Permeability lower than conventional syst. Compressive strengths for plugs at low density Gas tight set cements at any slurry density

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• • • • •

DensCRETE DensCRETE gives you better well control during cementing Simplified slurry design Improved Rheology at high density High pore pressure

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• • •

DeepCRETE DeepCRETE slurries cement weak, deepwater-zones and let you return to drilling faster Schlumberger Private

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SqueezeCRETE SqueezeCRETE repairs well problems when cements won’t

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Casing leaks Liner tops Channels behind casing Gravel packs Water zones

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– – – – –

Conventional cement jobs won’t last Temperature changes in upper casings

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Mud-weight changes

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Tectonic activity

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Formation changes

•

Well construction / completion damage

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•

FlexSTONE

– Density range: 12 - 18 ppg – Temperature: 50 - 350F – Expansion: up to 3%

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Operating range

FlexSTONE (Cont.)

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FlexSTONE Plaster Foam

Compressible

Salt cement 0

0.5

1

1.5

2

Expansion (%) 59

2.5

3

3.5

DuraSTONE Operating Range

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– Density Range: 9 - 25 ppg – Temperature: 50 - 450F – Flexural strength: 3X conventional cement

DuraSTONE (Cont.)

6 impacts with Class G

DuraSTONE

m = 8.5 kg

0.6 m

Sample : 5x5x5 cm Blow of 50 N.m 61

82 impacts

96 impacts

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Conventional cement

DuraSTONE (Cont.)

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Milling windows Multi-lateral drilling Bi-centered drilling High density perforating

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• • • •

DuraSTONE (Cont.)

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Conventional cement

DuraSTONE 63

DuraSTONE (Cont)

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Conventional cement

DuraSTONE

CemNET • Features

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

– Extremely effective with CemCRETE systems • Better plugging effect due to PSD • Lower rheology 65

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– Advanced fibers mixed with cement to seal lost circulation – Engineered to an optimal size – Inert

CemNET (Cont.) • Applications Used across fractures, fissures, vugs, and permeable zones Temperature limitation up to 450 0F Used for cement plugs and primary cementing operations Not for mud applications

• Benefits

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– – – –

– Easy to handle – No cement fall back – Cure losses during primary cementing • It is always preferred to cure losses prior to cementing

– Reduces disposal costs by reducing cement excess returns 66

CemNET (Cont.) • Dry fibers are bound together

– Easy to handle and add to cement

• Well dispersed fibers once agitated – High plugging efficiency

• Water wetting effect by the surfactant • Fibrous network across loss zones 67

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• No fiber lumps in mixing fluid

CemNET (Cont.)

Losses

Losses

Losses

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Circulation

Fibrous network across lost circulation zones

CemSTREAK Lightweight Low maintenance Compact design 4 wheel drive Easy Operation Reduced operational time • less associated risks to operation

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• • • • • •

CemSTREAK (Cont.) 1 Triplex pump 2 Centrifugals 2 Displacement tanks 300 hp Caterpillar engine (170 hhp) • 125 ft treating hose • 3000 psi max working pressure

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• • • •

What is Solids Fraction (SF)?

• Porosity is the percentage of Water in the Slurry Porosity (%) = Volume Water / Volume Slurry

Solids Fraction + Porosity = 1 71

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• Solids Fraction is the percentage of Blend in the Slurry SF(%) = Volume Blend / Volume Slurry

New Technology - Summary • CemCRETE – LiteCRETE, DenseCRETE – FlexSTONE, DuraSTONE

• CemNET – Advanced fibers mixed with cement to seal lost circulation

• CemSTREAK – Faster, Cleaner, More efficient

• SFM (Solids Fraction Monitor) – Qualitative measurement of slurry

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• CemSTONE

Break

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15 Minutes

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Discussion

What can go wrong? DESIGN

PREVENTION / MITIGATION Verify / Discuss Verify from logs / offset wells Reviewed by WE and WSS Reviewed by WE and WSS Never use for cementing design

ACTION PLAN QA/QC on well program Graphical and tabular data must be available Redesign the program QA/QC on cement program Use BHCT from cementing simulator

EXECUTION CRITERIA Equipment failure Wrong equipment Wrong mix fluid Density mixed not as per program Top plug accidentally released Over-displacement

Contamination

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PREVENTION / MITIGATION Maintenance record must be available Checklist to be reviewed and approved Volumes, additives must be checked vs the recepi Competent cementer and equipment in good condition Witness loading and releasing the plugs Verify displacement volumes. Know pump efficiency Know maximum overdisplacement Use LAS as much as possible Use dedicated tank Briefing of Mud Engineer and Derrickman

ACTION PLAN Function tested (I.e pressure or HHP test) / Backup system available Send equipment as per approved checklist Calculations must be double check Well maintained mixing system and competent cementer Cement head in good condition preferably with tatter tail For small casing sizes, consider increasing shoetrack length Consider pumping cement behind the top plug Never exceeds maximum overdisplacement Tanks must be clean Lines must be flush

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CRITERIA Wrong well data Wrong BHST Wrong additive Wrong cement program MWD BHCT for cementing temperatures

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End of Day 3