Copyright 2003, SPE/IADC Drilling Conference This paper was prepared for presentation at the SPE/IADC Drilling Conference held in Amsterdam, The Netherlands, 1921 February 2003. This paper was selected for presentation by an SPE/IADC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers or the International Association of Drilling Contractors and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the SPE, IADC, their officers, or members. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers or the International Association of Drilling Contractors is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract Data gathered from 15 (5 conventional, 10 foam) production wells on the Eldfisk field in the North Sea indicate that foam cement outperforms conventional cement for zonal isolation and dynamic curing of losses.

Drilling in a highly fractured reservoir presents problems related to losses and providing effective zonal isolation across the producing interval. Nearly all recent wells drilled in the Eldfisk Field have encountered losses in the magnitude of 250 to 300 bbl/hr.

Considering the downhole conditions, with pore pressures ranging from 4 to 10 lb/gal in the different productive layers, the importance of zonal isolation, establishing barriers in water productive layers, and achieving overall cement coverage is extremely important.

Because the reservoir section in the Eldfisk Field is mainly chalk, permeability is generally low. If not stimulated, the economics of drilling in this field would be marginal. The overall success of the drilling effort is therefore dependent on the stimulation results, which in turn depend largely on effective zonal isolation/cement coverage across the productive interval.

Foamed cement has been introduced and seems to have fulfilled the requirements of cementing in this challenging field. Since its introduction, the service companies have performed ten jobs successfully. The criteria for success have been measured using each of the following factors: operational performance, fluid diversion during stimulation, and CBL evaluation.

This paper provides details about the following:

Design review Operational challenges related to strict environmental

rules Handling foam cement returns at surface

Case review of the stimulation result Possible conformance Hydraulic fracturing CBL results from one well

Introduction

The following case study demonstrates that the unique properties of foamed cement can enable it to outperform conventional and lightweight cement systems in highly demanding reservoirs such as those in the Eldfisk Field. General Field Description The Eldfisk Field, discovered in 1970, is located in the southern section of the Norwegian North Sea in Block 2/7. This field is a high-porosity, low-permeability Ekofisk/Tor chalk reservoir. The initial reservoir pressure of the field was 6,800 psia and the static bottomhole temperature (BHT) is 268F. The true vertical depth (TVD) of the main reservoir section is from 9,800 ft to 12,000 ft. This field has produced 427 MMbbl of oil, 24 MMbbl of water, and 1,505 Bcfg. The current average reservoir pressure is about 3,000 psi. Waterflooding of this reservoir started in 2000. To help optimize the recovery of the reservoir, most of the vertical production and injection wells have been sidetracked and drilled horizontally.

The reservoir depletion to less than seawater gradient has greatly affected the drilling and completion practices. Currently, an 8.6-lb/gal seawater mud system is used for drilling the depleted reservoir section. This creates a high potential for lost-circulation problems. When excessive lost circulation occurs, a floating mud cap concept is used by which the annulus is kept full while drilling continues.1 On several wells, drilling has continued with losses of over 300 bbl/hr. Cement Job Design The Eldfisk field requires a cementing system that reduces the risk of lost circulation, while simultaneously delivering excellent annular displacement efficiency with the aim of achieving 100% annular fill. When set, the cement must exhibit complete zonal isolation for the life of the well (stimulation, production, selective work over), while providing lateral pipe support to combat compaction-induced failures. Foamed cement seems to fulfill these requirements.

In addition to the normal requirements of a cemented production liner, foamed cement is considered suitable for the

SPE/IADC 79912

Foam Cementing on the Eldfisk Field: A Case Study K. Green, SPE, Phillips Petroleum Co., Norway; P.G. Johnson, SPE, Phillips Petroleum Co., Norway; and Rune Hobberstad, SPE, Halliburton, Norway

2 SPE/IADC 79912

Eldfisk wells because it can offer several other unique advantages discussed in the following paragraphs. Lower Hydrostatic Pressure. Circulation losses while drilling and cementing in this field are common. Although the vertical height between total depth (TD) and the liner top is not great in general, a reduction of cement density from 15.9 to 11.5 lb/gal will reduce the hydrostatic pressure in the horizontal section by an average of 350 psi.

Dynamic Control of Losses. The thixotropic and expansive nature of foam, together with the structural features of the bubble cells, helps reduce losses to vuggy or fractured formations and helps reduce fluid loss to permeable formations.

Strength-to-Density Ratio. Foamed cement slurries can achieve considerably higher strengths than low-density slurries extended using additional water.

Mechanical Properties of Set Cement. The high ductility and bubble structure of foamed cements has been shown to be beneficial when the cemented annulus is subjected to thermal and mechanical loading. These features of foamed cements can enable internal deformation without cracking. This property also helped combat liner collapses that have occurred on the Eldfisk Field as a result of subsidence.2-4 Hole Cleaning. The high apparent viscosity of foamed fluids can enable them to exceed the shear stress required to mobilize highly gelled muds and to exhibit superior solids-carrying capability.5-7 Environmental Considerations During the design phase and initial planning for the introduction of foamed cement in the North Sea, one of the major driving forces behind the choice of cement slurry was consideration for the environment.

The ever increasing push from the Norwegian government to use chemicals that pose little or no risk (PLONOR-approved) and employ the zero-discharge philosophy led to the development of a foam cement system containing mostly PLONOR-approved chemicals and a system to safely contain foam cement circulated out of the well.

In the Eldfisk foamed cement slurry, there was a substantial reduction in the number of chemicals used, compared to the nonfoamed cement slurries being pumped. Only one chemical in the foamed cement slurry was not on the PLONOR list vs. three for the conventional slurry design. The major components in the slurry composition were all PLONOR approved, and there was no need for the poorly biodegradable polymers often used in conventional slurries.

Due to lower chemical requirements and the environmental properties of the chemicals used, foamed cement is one of the most environmentally friendly zonal isolation systems available.

Slurry Choice and Design The base cement slurry was designed according to the following criteria:8

No anti-foaming chemicals to prevent destabilizing the foam cement

High ratio of reactive solids to water for higher compresive strengths

Accelerators, retarders, or other chemical additives should be non-dispersing to prevent further destabilizing the foam cement

Silica is used to combat strength retrogression at temperatures greater than 230F

In general, defoamers and dispersants tend to destabilize foamed cement, while admixes that increase viscosity or add thixotropy tend to stabilize.

Fluid-loss control agents are not always needed with foamed cements due to the inherently low fluid-loss aspects of foams. In addition, foamers and foam stabilizers are critical to foam properties; tested and proven with respect to compatibility, capability, and foam stability; and effective through the wellbore temperature range.

Note that the foamer used was the non-PLONOR chemical. Initial slurry lab test results are described in Table 1.

Computer-Aided Job Design Table 2 shows the main parameters for the dynamic placement program used during the placement design phase.

Employing a computer program in a foamed cement job design is recommended. The software can enable accurate determination of the following parameters:

Annular volume from caliper log Equivalent circulating density (ECD) Surface pressure Nitrogen concentration Hydrostatic profile Displacement efficiency (erodibility)

In addition, the dynamic placement program was used to

rerun previous jobs. The recorded data was loaded into the simulator and the service companies acquired valuable information regarding the job execution that was then taken into consideration on the next job. Figs. 1, 2, and 3 show these printouts. Spacer Design Types of Spacer Used. To help ensure high job performance, it was essential that the design phase include a spacer system that could enable proper mud removal and water wetting of the casing and formation.

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For the jobs performed with water-based mud (WBM) in the hole, water was recommended, for the following reasons:

To avoid free-fall (U-tubing) and resultant loss of job

control and foam overexpansion To reduce hydrostatic and ECD towards end of

displacement High density was not required for well control Improved displacement efficiency resulting from

highly turbulent flow flush, followed by foam When oil-based mud (OBM) was present in the wellbore, a conventional turbulent flow, weighted spacer was used with density intermediate between the mud and cement slurry.

The first half of the spacer contained mud-thinning and water-wetting surfactants, whereas no chemicals were added to the second half to avoid the possibility of destabilizing the foam. Equipment Layout Performing a foamed cementing job requires specialized equipment and computer design programs. A foam generator that creates an 800- to 1,000-psi pressure drop is needed to provide the required shear energy to promote stable foam with small discrete bubbles. An automated nitrogen unit slaved to the base slurry rate can provide consistent surface and downhole slurry densities. The foamed cement process fully integrates the automation for all parts of the cementing job. All equipment is linked together and operates according to the rate of slurry production. Fig. 4 shows the required instrumentation and overall layout of the operational rig up.

NORSOK (the competitive standing of the Norwegian offshore sector) is the industry initiative to add value, reduce cost and lead time, and eliminate unnecessary activities in offshore field developments and operations. All of the equipment used for the foamed cement operation complies with these standards (NORSOK Z-015).

The complete NORSOK standard is comprehensive and includes governing regulations for all aspects of the drilling operation. For the mobile equipment (Z-015) used in the foamed cement jobs, requirements included: Sound insulation for diesel units Automatic fire and gas detection Electrical shutdown mechanism connected to the drilling

emergency shutdown system (ESD) system Job Execution Liner Running and Configuration. After setting a 9 5/8-in. whipstock at 5,170 ft TVD, an 8 -in. 9 7/8-in. bicenter hole was drilled to within +/- 10 ft TVD of the Ekofisk formation. A 7 -in. liner was then set and cemented conventionally at approximately 9,500 ft TVD at an approximately 60 angle. The 6 -in. hole was drilled horizontally through the Ekofisk and Tor formations (Fig. 7). A 5-in. liner was then run through this section and foam cemented, using a remote-operated cementing head. This liner-hanger system was hydraulically set with a mechanically set liner top packer. To increase the

chances of bumping the plug, all of the liner joints were calipered to determine the exact ID, and a four-joint shoe track was run. To increase the chances of rotating the liner during the cement job, the liner was filled with seawater containing a graphite friction reducer that also acted as a loss-circulating material. Pumping Schedule. Measurement of surface foam density is seldom attempted in the field. Therefore, careful monitoring of pressures and temperatures and accurate control of mixing ratios of nitrogen, base slurry, and surfactant are recommended for a successful operation. To help enable accurate placement and a consistent downhole density, job-controlling volume schedules are employed. The design of these tables can enable accurate spot checks and volumetric control of the fluids as they are being pumped.

Designing a foam cement job and executing the plan accordingly requires accurate quality control during the pumping sequence. Base slurry density should be controlled using a recirculating mixer and radioactive densiometer (RAD) upstream and downstream from the surfactant addition point. Periodically, the density should be physically verified using a pressurized balance. Base slurry flowrate should be measured using a stroke counter and flowmeter (Fig. 8). The nitrogen unit should be slaved to the base slurry rate so that any changes in base slurry rate are compensated with a change in nitrogen rate. Nitrogen flowrate from the flowmeter should also be crosschecked against the pump stroke counter flowrate and the pressure drop across the foam generator to help ensure accuracy. The surfactant rate should be measured with a flowmeter and verified with tank gauging.

With this information, the surface density can be calculated using a computer simulation program. This should be the design target. As illustrated in the graph in Fig. 9, the job-control function was excellent. It should be noted that the densities calculated using the nitrogen driveshaft counter were considered erroneous for unknown reasons; this highlights the need for close monitoring of all the flowrates using several methods. Similar calculation techniques used to measure surface density can be used to calculate the density of the foam under downhole conditions (Fig. 10). Job-Control Functions The foamed cement process includes the use of fully integrated automated systems to help ensure that the cementing operation proceeds according to design for the best possible results.

In addition to the fully automated system, in offshore operations, we also employ real-time data transfer to the onshore support staff. All of the vital job controls and data acquisition are fully integrated in an onshore operations room.

Although no actual job control was given to the onshore support team in this case, the entire foamed cement process encourages and promotes real-time operations.

Through computer software that allows real-time calculations of ECD and erodibility, placement dynamics can be accurately determined and controlled. In late 2002, ConocoPhillips will have a fully operational onshore drilling center that will allow all the cement jobs (not just the foamed

4 SPE/IADC 79912

cement jobs) to be performed with the help of real-time operations and onshore support.

Handling Foam at Surface Defoaming Manifold and Process. The major difference between the foamed cementing operation and normal cementing operations is the introduction of nitrogen into the cement. Nitrogen is generally safe to work with because it is nonflammable, nonpoisonous, and nonpolluting. Nevertheless, general safety rules relating to nitrogen service should be adhered to, such as chaining down energized lines, placing drip pans beneath the nitrogen unit to prevent damage to the platform, wearing personal protective gear, etc. Environmentally, foam cementing results in significant challenges in a zero-discharge environment if nitrified cement must be brought back to surface. This situation could occur after circulating from the liner top at the end of the cement job. The expansion of the foam (1 bbl downhole = 70 bbl on the surface9), can cause considerable uncertainty about how to handle the large volumes of foam safely with the pit space available on the platform. The conventional approach to handling foamed cement circulated out above a liner top packer on an offshore installation is to leave it in place, drill the cement out in the 7 -in. casing in one trip, and on a second trip, clean out the 5-in. liner.

To eliminate one trip, a defoaming process was developed (Figs. 4 and 5) to help ensure zero discharge by breaking the foam at surface and separating the liquid and gas phases. This was done using a manifold system that allowed reverse circulating the contents above the liner top packer through the cement head where an OBM containing a cementing retarder was injected to break the foam and retard the base slurry. The mixture was then pumped across a choke for a shearing effect and into the rigs poorboy degasser. The nitrogen was then vented to the derrick and the retarded defoamed slurry was pumped to the cuttings reinjection well for disposal. This enabled the nitrogen to be vented in a safe and controlled manner and reduced the pit volumes needed. Because of the high ECD caused by reverse circulation, this process requires bumping the liner wiper plug. If the plug is not bumped, there is considerable risk of a wet shoe.

The overall operation of circulating out cement from the top of the liner and reinjecting it complies with the zero-discharge philosophy and was vital in the overall success of this project. Computer-Based Control. A means for accurately predicting the foam cement volumes being circulated out was essential to the success of the operation. A series of computer simulations correlated the volumetric expansion of the foam cement as the pressure slowly decreased toward surface conditions. Tables and graphical presentations from these simulation runs yielded control functions for when to initiate the defoaming process, how much defoaming fluid to pump, and what pressures to expect. Examples of these charts can be found in Fig. 6. Post-Job Review The typical Eldfisk horizontal well is perforated over 15 intervals, spaced about 250 to 300 ft apart. Each interval is

approximately 1 ft long, with a perforation density of 6 to 8 shots per ft. A typical stimulation attempts to acid-fracture each interval with a single treatment, often divided into stages consisting of gel, acid, diversion, and overflush. Thus, good zonal isolation is needed to ensure that each interval is stimulated.

With good zonal isolation, wellhead-treating pressures throughout the stimulation job exhibited a characteristic stairstep pattern. Such behavior is indicative of diversion balls sealing off those zones taking the most stimulation fluids and stimulation fluids moving to other open intervals but requiring more pressure to overcome casing and liner friction pressure losses. Without exception, the team produced the desired stairstep pattern on the wells completed with foam cement (Figs. 11 and 12). Conventional cements rarely show this stairstep behavior. In fact, many jobs exhibit wellhead treating pressures that go to vacuum due to lack of sealing behind the pipe. Cement Bond Evaluation. Methods to evaluate conventional cements with logging data may not yield valid results in foamed cements. These methods rely on the contrast of acoustic properties of the materials in the annulus. When using low-density foam cements, the acoustic properties are similar to those of the wellbore fluid. Therefore, the resulting poor CBL attenuation and minimal contrast in acoustic impedence invalidate standard data processing techniques. Logging tools commonly used in foam cement evaluation are the traditional cement bond log (CBL) tools and the modern ultrasonic scanning tools.10

CBL tools provide waveform images and acoustic amplitudes that together help describe cement-to-pipe and cement-to-formation bonding. Ultrasonic scanning tools contribute circumferential images and detailed information regarding the cement-to-pipe bond.

Although the average absolute value of acoustic impedence of foam cement is typically similar to wellbore fluids or gases, it is still possible to distinguish cement using statistical variation techniques. This is because the solid crystalline structure of cement exhibits a high degree of impedence variation compared to a fluid. This statistical interpretation method correlates the two datasets and can enable accurate determination of cement quality.

The statistical variance method was applied to the ultrasonic and acoustic data gathered from one of the Eldfisk wells cemented with foam. The results were very good. Although complete losses were experienced throughout the entire liner running and cementing, results from the log showed 81% coverage in the production interval. Conclusion The results gathered from the stimulation work, overall operational execution, and cement bond evaluation indicate that foamed cement fulfilled the initial requirements for cementing in the Eldfisk field.

The operational aspect of performing foam cement jobs in the North Sea has been overcome. Challenges related to strict environmental regulations and equipment standards have been met and overcome.

SPE/IADC 79912 5

The improved stimulation results have led to discussions regarding extended treatments in the future, including hydraulic fracturing and potential conformance treatments.

Zonal isolation is a critical factor to properly stimulate the well and perform water shutoff. In wells that are proppant-fractured, good zonal isolation is necessary. Proper placement of proppant and the expense of such treatments dictate that zonal isolation be fundamental to success. Many of the new Eldfisk wells (both production and injection) are horizontal, with lengths ranging from 2,000 to 5,000 ft. Because the flooding pattern is rather complicated and sometimes unpredictable, water shutoff must be possible. Foamed cements can enable the operator to consider and implement many conformance technologies because each producing interval is isolated from the others.

The Eldfisk case study reflects the excellent performance of foamed cement. The cements properties give the cements superior placement qualities and excellent long-term zonal isolation features. Acknowledgments The authors wish to thank the following groups and individuals for their contributions to this paper:

ConocoPhillips and Halliburton management Co-ventures: TotalFinaElf, Norsk AGIP, Statoil,

Norsk Hydro, and Petoro Operational team Operational management Onshore support staff Ian McPherson

References 1. Anvik, H.K. and Gibson, W.R.: Drilling and Workover

Experiences in the Greater Ekofisk Area, paper IADC/SPE 1650 presented at the 1987 SPE/IADC Drilling Conference, New Orleans, Louisiana, 15-18 March.

2. White, J., Moore, S., Miller, M., and Faul, R.: Foaming Cement as a Deterrent to Compaction Damage in Deepwater Production, paper SPE 59136 presented at the 2000 IADC/SPE Drilling Conference, New Orleans, 23-25 February.

3. Goodwin, K.J. and Crook, R.J.: Cement Sheath Stress Failure, SPEDE (December 1992) 291 (SPE 20453).

4. Thiercelin, M.J., Dargaud, B., Baret, J.F., and Rodriguez, W.J.: Cement Design Based on Cement Mechanical Response, SPEDE (December 1998) 266-273 (SPE 38598).

5. Ravi, K.M, Beirute, R.M., and Covington, R.L: Erodibility of Partially Dehydrated Gelled Drilling Fluid and Filter Cake, paper SPE 24571 presented at the 1992 Annual SPE Technical Conference and Exhibition, Washington, D.C., 4-7 October.

6. Griffith, J.E. and Osisanya, S.: Thickness Optimization of Drilling Fluid Filter Cakes for Cement Slurry Filtrate Control and Long-Term Zonal Isolation, paper SPE 29473 presented at the 1995 SPE Production Operations Symposium, Oklahoma City, Oklahoma, 2-4 April.

7. Smith, T.R. and Ravi, K.M.: Investigation of Drilling Fluid Properties to Maximize Cement Displacement Efficiency, paper SPE 22775 presented at the 1991 Annual SPE Technical Conference and Exhibition, Dallas, Texas, 6-9 October.

8. RP 10B, Recommended Practice for Testing Well Cements, 22nd edition, API, Dallas (December 1997).

9. Foam Application Manual, Nitrogen Data for Oil Well Servicing, (Halliburton P/N 252.11115, 1992).

10. Frisch, G.J., Graham, W.L., and Griffith, J.: Assessment of Foamed CementCement Slurries Using Conventional Cement Evaluation Logs and Improved Interpretation Methods, paper SPE 55649 presented at the 1999 Rocky Mountain Regional Meeting, Gillette, Wyoming, 15-18 May.

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Portland G CementLiquid Additives, gal/secWater, gal/sec

Total Mixing Fluid, gal/secDensity, lb/galYield, ft3/sk

Foamer, gpsDensity with Foamer, lb/galNitrogen Quality, %Downhole Density, lb/gal

Time to 30 Bc, hr:minTime to 70 Bc, hr:minTime to 100 Bc, hr:minBc Units at Test Temperature

Temperature, F 80 194300 rev/min 79 33200 rev/min 59 25100 rev/min 36 1760 rev/min 24 1430 rev/min 17 116 rev/min 7 103 rev/min 6 8Gel Strength, 10sec/10min 2 15Plastic Viscosity (PV) 65 24Yield Point (YP) 15 9Foam Blender Time, secFoam Stability, lb/gal 11.68 11.76

50 psi Compressive Strength, hr:min500 psi Compressive Strength, hr:min24 hr Compressive Strength, psi

94 lb/sk1.384.5

5.8815.31.26

0.1415.21

27

5:501-8

11.2 to 11.6

5:37

10:592,000

Table 1Laboratory Test Results

Thickening Time

Fann Data

15

9:32

5:45

Design Open Hole Size 8.98 in. (20% annular xs)Foam Quality 20 to 30% Foam Design Method Constant nitrogenBase Slurry 15.3 lb/gal Dyckerhoff GBack Pressure Zero (atmospheric)Surface Pressure Preferrably > zeroWell Fluid 8.7 lb/gal WBMBase Slurry Pump Rate 4 to 6 bbl/minSurface Iron 2-in. iron: 100-ft run, rising 30 ftFlush/Spacer 70 bbl, 8.34 lb/gal

Table 2Computer Program Input Parameters

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Base Slurry 15.3 N2 Conc. 286.0 (scf/bbl)

Yield 1.26 (ft^/sk) N2 Choke 12 (/64 in.)

Water Ratio 5.88 (gal/sk) Foamer Rate 2.58 (gal/min)

Cement Rate 4.0 (bbl/min) Foamer Rate 15.38 (gal/1,000 gal cement)

Mix H2O 5 (increment bbl) Foamer Conc. 0.140 (gal/sk)

Surf Depth 0.088 (cm/ltr)

Rates and Pressure VolumeCement Surfactant Nitrogen Nitrogen Surfactant Volume Volume Cement Mixing Volume

Rate Rate Rate Pressure depth Surfactant Nitrogen pumped Water Cement(bbl/min) (gal/min) (SCF/min) (psi) (cm) (gal) (scf) (bbl) (bbl) (sk)

1.5 0.97 429 1,023 0.7 2.0 917 3 2 141.6 1.03 458 1,093 2.3 7.0 3,209 11 7 501.7 1.10 486 1,162 4.0 12.0 5,501 19 12 861.8 1.16 515 1,231 5.7 17.0 7,793 27 17 1211.9 1.23 543 1,300 7.3 22.0 10,085 35 22 1572.0 1.29 572 1,369 9.0 27.0 12,378 43 27 1932.1 1.35 601 1,439 10.7 32.0 14,670 51 32 2292.2 1.42 629 1,508 12.3 37.0 16,962 59 37 2642.3 1.48 658 1,577 14.0 42.0 19,254 67 42 3002.4 1.55 686 1,646 15.7 47.0 21,546 75 47 3362.5 1.61 715 1,715 17.3 52.0 23,838 83 52 3712.6 1.68 744 1,785 19.0 57.0 26,130 91 57 4072.7 1.74 772 1,854 20.7 62.0 28,423 99 62 4432.8 1.81 801 1,923 22.3 67.0 30,715 107 67 4792.9 1.87 829 1,992 24.0 72.0 33,007 115 72 5143 1.94 858 2,061 25.6 77.0 35,299 123 77 550

3.1 2.00 887 2,131 27.3 82.0 37,591 131 82 5863.2 2.06 915 2,200 29.0 87.0 39,883 139 87 6213.3 2.13 944 2,269 30.6 92.0 42,176 147 92 6573.4 2.19 972 2,338 32.3 97.0 44,468 155 97 6933.5 2.26 1,001 2,407 34.0 102.0 46,760 163 102 7293.6 2.32 1,030 2,477 35.6 107.0 49,052 172 107 7643.7 2.39 1,058 2,546 37.3 112.0 51,344 180 112 8003.8 2.45 1,087 2,615 39.0 117.0 53,636 188 117 8363.9 2.52 1,115 2,684 40.6 122.0 55,928 196 122 8714.0 2.58 1,144 2,753 42.3 127.0 58,221 204 127 9074.1 2.64 1,173 2,823 44.0 132.0 60,513 212 132 9434.2 2.71 1,201 2,892 45.6 137.0 62,805 220 137 9794.3 2.77 1,230 2,961 47.3 142.0 65,097 228 142 1,0144.4 2.84 1,258 3,030 49.0 147.0 67,389 236 147 1,0504.5 2.90 1,287 3,099 50.6 152.0 69,681 244 152 1,0864.6 2.97 1,316 3,169 52.3 157.0 71,973 252 157 1,1214.7 3.03 1,344 3,238 54.0 162.0 74,266 260 162 1,1574.8 3.10 1,373 3,307 55.6 167.0 76,558 268 167 1,1934.9 3.16 1,401 3,376 57.3 172.0 78,850 276 172 1,2295.0 3.23 1,430 3,445 59.0 177.0 81,142 284 177 1,2645.1 3.29 1,459 3,515 60.6 182.0 83,434 292 182 1,3005.2 3.35 1,487 3,584 62.3 187.0 85,726 300 187 1,3365.3 3.42 1,516 3,653 64.0 192.0 88,018 308 192 1,3715.4 3.48 1,544 3,722 65.6 197.0 90,311 316 197 1,4075.5 3.55 1,573 3,791 67.3 202.0 92,603 324 202 1,4435.6 3.61 1,602 3,861 69.0 207.0 94,895 332 207 1,4795.7 3.68 1,630 3,930 70.6 212.0 97,187 340 212 1,5145.8 3.74 1,659 3,999 72.3 217.0 99,479 348 217 1,5505.9 3.81 1,687 4,068 74.0 222.0 101,771 356 222 1,5866.0 3.87 1,716 4,137 75.6 227.0 104,063 364 227 1,6216.1 3.93 1,745 4,207 77.3 232.0 106,356 372 232 1,6576.2 4.00 1,773 4,276 78.9 237.0 108,648 380 237 1,693

Table 3Job Control Sheet, Foam Cement

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Fig. 1ECD plot.

Fig. 2Surface pressure.

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Fig. 3Displacement efficiency (erodibility) plot.

Fig. 4Operational rig up.

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Fig. 5Eldfisk defoaming manifold.

Fig. 6Defoaming control plot.

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Fig. 7Eldfisk well schematic.

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Fig. 8Nitrogen, base slurry, and foamer flow data.

Fig. 9Density of base slurry and foamed cement.

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Fig. 10Downhole foam density.

Fig. 11Eldfisk stimulation curves, normal jobs.

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Fig. 12Eldfisk stimulation curves, foam jobs.