Experimental Investigation Of Silica Fume As A Cement .
Iranian Journal of Chemical EngineeringVol. 7, No. 1 (Winter), 2010, IAChEExperimental Investigation of Silica Fume as a Cement Extenderfor Liner Cementing in Iranian Oil/Gas WellsS. R. Shadizadeh1 , M. Kholghi1, M. H. Salehi Kassaei21- Petroleum University of Technology, Department of Petroleum Engineering, Ahwaz, Iran.2- National Iranian South Oil Company.AbstractSilica fume is a by-product of silicon metal or ferrosilicon alloys in smelters usingelectric arc furnaces. It consists of 85% to 95% amorphous silicon dioxide (SiO2). Eachindividual particle of silica fume is spherical with average diameter 0.15-0.3 μm (100times finer than cement particle); therefore its specific surface area is high. Silica fumeparticles are water wet and absorb excess water in cement slurry when cement slurry isextended by water. Silica fume thickens the cement slurry, so rheological properties arecontrolled by dispersants. In this paper, optimal concentration of silica fume and otheradditives for preparing 90 pcf cement slurry for liner cementing in one Iranian oilfieldis determined. The criteria of designing slurry formulation are slurry density,rheological properties, fluid loss, free water, thickening time of cement slurry, andcompressive strength and permeability of set cement. Finally, based on experimentalresults, the preferable slurry compositions are selected. This formulation can be usedfor cementing of oil and gas wells where moderate and light weight cement density isneeded.Keywords: Cement Extender, Light Weight Cement Density, Silica Fume, CementSlurry, Permeability of Set Sement, Compressive StrengthIntroductionCement extenders are a routine additive usedfor reducing slurry density and increasing theyield of cement slurry. A reduction of slurrydensity reduces the hydrostatic pressureduring cementing; this helps to cement oiland gas wells in low pressure or depletedreservoirs and prevent induced lostcirculation because of the breakdown ofweak formations. In addition, the number ofstages required to cement a well may be Corresponding author: shadizadeh@put.ac.ir42reduced. Extenders reduce the amount ofcement required to produce a given volumeof set product which results in a greatereconomy. Different types of cementextenders additives, such as bentonite,pozzolans, microspheres and foam cementare used for preparing light weight cementslurry.Silica fume can serve as an extender byallowing an additional 0.532 gallons of mixwater to be added to the slurry per pound of
Experimental Investigation of Silica Fume as a Cement Extender for Liner Cementing in Iranian Oil/Gas Wellssilica fume (4.4 cc water/gr. silica fume).[1]Some other names of silica fume aremicrosilica and condensed silica fume.Silica fume consists of 85% to 95%amorphous SiO2. Its particles are very fine(95% of SiO2 are less than 1µm), andtherefore act as a microfiller in a set cementmicro-structure and it is a reactive solid topozzolanic reaction with free lime in normaltemperature.[1,2] Trace elements in silicafume depend upon the type of fume; usually,these materials have no impact on theperformance of silica fume.[3]P.K. Mehta and O.E. Gjorv[2] in 1982 hadcompared the compressive strength ofconcrete containing the fly ash and silicafume. The specimens containing the silicafume showed considerably higher strengths,even at early and 90-day ages of curing, thetheir compressive strength was almost twiceas much as the control.At a fixed slurry density, increasing the silicafume concentration improves the earlycompressive strength development andreduces the free water, but it slightlyincreases the slurry viscosity.Silica fume particles act as particulatematerials in filter cake to reduce the fluidloss of slurry into the permeable formation.Silica fume particle size is very small (lessthan 0.5 μm), and therefore can enter thefilter cake and lodge between the cementparticles, block the narrow passage of fluid,and finally, decrease the permeability ofcement cake.Increase of water to cement ratio (WCR) ofcement slurry causes the cement permeabilityto increase [4]. In water extended cementslurry the WCR is high, but Golapudi et.al.[5] had observed significant reduction inIranian Journal of Chemical Engineering, Vol.7, No.1gas permeability when silica fume/fly ashwas blended in cement. In addition, silicafume prevent the chloride and sulfate ionspenetration.Blomberg et. al.[6] and Grinrod et al.[7]observed that silica fume has a gas migrationcontrol effect. If static gel strength of cementslurry quickly increase from 100 lb/l00ft2 to500 lb/l00ft2 (often referred to as the cementslurry transition), then it is viewed asfavorable for restricting gas percolationthrough the unset cement. In gas-tightcement, a transition time less than 30 min isrecommended. A key ingredient in thecement design is high fineness amorphoussilica that produces several important gastight properties.[8] In this paper, the optimalconcentration of silica fume and otheradditives for preparing 90 pcf cement slurryfor liner cementing in one Iranian oilfield isdetermined. The criteria of designing slurryformulation are slurry density, rheologicalproperties, fluid loss, free water, thickeningtime of cement slurry, and compressivestrength and permeability of set cement. Thefollowing section describes the procedures offormulating the slurry compositions 90 pcfcement.Material and MethodSilica fume is obtained from Iran FerrosiliceCompany. Table 1 shows the Physicochemical properties of silica fume (SF).Class G type HSR Dyckerhoff cement is usedas Portland cement and its chemical analysisis given in Table 2. Distilled water is used formaking cement slurry.Cement Slurry Design ParametersBefore cement slurry is pumped into a well,various laboratory tests can be conducted to43
Shadizadeh, Kholghi, Salehi Kassaeiensure proper placement and to assist inpredicting the performance and behavior ofthe slurry as it is pumped and after itsplacement. The following factors will affectcement slurry design[9]: Well depth and temperature Max. allowable pumping or thickeningtime Strength of cement required to supportcasing Quality of available mixing water Type of drilling fluid and its additive Slurry density Filtration controlTwo basic affecting factors on the downholeperformance of cement slurries are temperature and pressure.In this study, 90 pcf cement slurries aredesigned for 7 in liner cementing in oneIranian oilfield. Cement slurry density isreduced by increasing WCR and addingsilica fume as an extender additive.Liner shoe depth is approximately 2400-2500m and liner length is about 400-500 m. Thetemperature gradient (TG) of this field is1.15-1.2 F/100ft. The bottom hole statictemperature (BHST) is about 170-180 F andLiner lap static temperature is approximately160 F. According to Table 4 of APIRecommended practice 10B[10], TG andliner shoe depth, schedule 9.18 is selected.Also, Bottom Hole Circulating Temperature(BHCT), Heat up rate, initial pressure andfinal pressure are 132 F, 1.6 F/min, 650 psiand 5000 psi, respectively. Liner lap is thecritical point of liner; therefore liner lapstatic temperature is used for compressivestrength and water permeability tests.Minimum allowable pumping time for 7 inliner is approximately 180 (min), thereforethe minimum designed slurry ThickeningTime (TT) should be 180 min. The API fluidloss of cement slurries must be controlled to70 cc/30min.Table 1. Physicochemical properties of the used silica fume.Chemical composition, 0.90.6-1.5Average grain size0.2-0.3 µmSpecific surface area14000 m2/kgSpecific gravity2.2Bulk density200 kg/m3Color in bulkLight grayColor in slurryBlackTable 2. Chemical composition of class G Dyckerhoff cement.Chemical composition, 751.80.740.100.64Iranian Journal of Chemical Engineering, Vol. 7, No. 1
Experimental Investigation of Silica Fume as a Cement Extender for Liner Cementing in Iranian Oil/Gas WellsWell Cement Tests ProceduresAmerican Petroleum Institute (API) haspresented “Recommended practice for testingwell cements”, API recommended practice10B[10], attempting to unite the well cementtest procedures worldwide. These tests weredevised to help drilling personnel todetermine if a given cement composition willbe suitable for given well conditions. APIRP-10B[10] is used to determine the cementslurry and set cement specification.Slurry PreparationCement slurry was prepared according tosection 5 of API RP-10B [10]. The mixingmethod strongly affects slurry and set cementproperties. Cement additives can be dryblended or wet blended in cement slurry.When additives are added to mixed waterbefore cement, it is called wet blending.Sequence of adding additive and mixing timeare important in the wet blending method.The solution of cement slurry is prepared atlow rpm of mixer (4000 200 rpm).Slurry Density DeterminationSlurry density was determined according tosection 6.5 of API RP-10B.[10]Rheological PropertiesRheological properties and the gel strength ofcement slurry are measured according tosections 12.6 and 12.7 of API RP-10B[10],respectively. Before conducting tests, cementslurry was conditioned for 35 to 40 min in anatmospheric consistometer to BHCT. Duringthese tests, the temperature of the slurry waskept roughly fixed. Rheological properties ofcement slurry are determined by “Chan35 VG meter” of Chandler Engineering Company.Iranian Journal of Chemical Engineering, Vol.7, No.1Well Simulation Free Water TestFree water test of cement slurry is performedaccording to sections 15.2, 15.3, 15.4.1 and15.5 of API RP-10B[10]. Cement slurry wasconditioned for 35 to 40 min in anatmospheric consistometer to BHCT beforethe test. According to section 15.4.1 of APIRP-10B[10] the graduated cylinder must beimmersed in a water bath with a vibrationfree condition, but in this study, due to lackof an appropriate water bath, the graduatedcylinder was put in the circulated water bath.According to section 15.5 of API RP10B[10] the graduated tube must be static inambient temperature. The graduated cylinderwas held in vertical position because the wellwas assumed vertically.Static Fluid Loss TestFluid loss test was performed according tosection 10 of API RP-10B[10] and some ofthem are based on standard API filter presstest in which filtration pressure is 100 psi anddouble layer screen 325 mesh on top andsupport screen 60 mesh are used as thefiltration area. Cement slurry wasconditioned for 35 to 40 min in anatmospheric consistometer to BHCT beforetest.For tests that “blowout” before 30 min in thestandard API filter press, the followingequation is used for calculating standard APIfluid loss.Calculated standard API fluid loss Qt5.477tFor tests that “blowout” before 30 min inAPI fluid loss (filtration pressure is 900 psi),the following equation is used.45
Shadizadeh, Kholghi, Salehi KassaeiCalculated API fluid loss 2 Qt5.477tQt is the volume (cc) of filtrate collected atthe time t (min) of the blowout.Well Simulation Compressive StrengthTestSet cement compressive strength is achievedaccording to section 7 of API RP-10B[10] atatmospheric pressure after 24 hr curing in160ºF. Some of the cement slurries wereconditioned to BHCT before molding toprovide better simulation of the wellcondition.Permeability TestWater permeability of set cement isdetermined according to section 11 of APIRP-10B[10]. Cement slurry was molded in aspecial mold sample holder and cured at160ºF at atmospheric pressure. Some of thecement slurries were conditioned to BHCTbefore molding for better simulation of wellcondition. After removing permeabilitymolds from the curing water bath anddetaching the top and bottom plates,permeability molds are placed in a coolingbath for four hours. Curing time ofpermeability mold in water bath is 24hr.Well Simulation Thickening Time TestSlurry thickening time test was performedaccording to section 9 of API RP-10B[10] atatmospheric and pressurized consistometerconsistent with schedule 9.18.Slurry Solution StabilityAfter mixing the wet blend additives withmixed water, the solution is poured in a250(cc) graduated cylinder and put in rest46and free-vibration condition at ambient temperature. Accumulated free water on top ofthe slurry solution is monitored and recorded.Results and DiscussionExperimental results of 90 pcf cement slurrytests are graphed in this section. This dataconsist of cement slurry composition,density, rheological properties, fluid loss,free water, thickening time test of cementslurry,compressivestrength,waterpermeability of set cement and solutionstability.According to the additives concentration,different cement slurry compositions aredesigned in this study. Every cement slurrycomposition has a number used in thediscussion.90 pcf water extended cement slurry isprepared by using class G Dyckerhoffcement. 15% and 20% BWOC Silica fumeare used to hold excess water in cementslurry and to obtain stable cement slurry.D145A is a dispersant additive used todecrease the cement slurry rheologicalproperties. Also, D112 is a fluid loss controlfor high water to cement ratio (WCR) cementslurry[11] used to decrease the fluid loss ofcement slurry. At last BA-100S and NaCl areused in cement slurry. BA-100S is a bondingagent and anti gas migration additive of BJService Company and NaCl is a salt used toincrease the compressive strength of cement.Weight of cement slurry is decreased byincreasing the WCR of the slurry. The WCRof 100 pcf and 90 pcf cement slurry are 0.81and 1.22, respectively. Cement slurry and setcement properties of 100 and 90 pcf cementslurry are compared in Table 3.Iranian Journal of Chemical Engineering, Vol. 7, No. 1
Experimental Investigation of Silica Fume as a Cement Extender for Liner Cementing in Iranian Oil/Gas WellsTable 3. Cement slurry and set cement properties of100 and 90 pcf cement slurries.Properties100 pcf90 pcfPV (cp)YP (lbf/ 100ft2)4.8754.1253.752.2510 sec GS (lb/ 100ft2)3.5210 min GS (lb/ 100ft2)129.5Std Fluid Loss(cc/30min)1415.41741Free Water (%) at80 F9.627.6Compressive Strength(psi)1220150Water Permeability(md)0.015850.3391When the WCR of slurry increases from 0.81to 1.22, the rheological properties of cementslurry are decreased, but the free water ofcement slurry is increased drastically from9.6% to 27.6%. Standard FL of 100 and 90pcf cement slurry are 1415.4 and 1741(cc/30min), respectively. By increasingWCR, the solid fraction of cement slurry isdecreased; hence the thinner cement cake iscreated when a certain volume of cementslurry is in the filtration chamber, whereuponthe fluid loss of cement slurry is increased.WCR has a detrimental effect onCompressive Strength (CS) and waterpermeability of set cement. When the WCRis increased, the compaction of set cement isdecreased. Water of slurry occupies the porevolume in set cement.Pore volume acts as a stress concentrator inset cement and causes a decreases in thecompressive strength.[12] Set cement porevolume is directly related to WCR.Thickening time of high WCR slurry is long;long thickening time causes the the CS of setIranian Journal of Chemical Engineering, Vol.7, No.1cement to decrease. More excess water in 90pcf neat cement creates a wider channel inset cement, so water permeability of 90 pcfneat cement is 21.4 times more than thewater permeability of 100 pcf neat cement.A WCR of 90 pcf cement slurry is 1.22,whereas the API WCR is 0.44. High WCRcement slurry is unstable and its free waterpercentage is high. According to D.T.Mueller and R.L. Dillenbeck[1] therecommended 5 %BWOC and 10 %BWOCsilica fume do not provide stable slurrytherefore, 15% and 20% BWOC silica fumeare used to prepare cement slurry.PV and YP of 90 pcf cement slurry with 0%,15% and 20% BWOC silica fume (SF) areshown in Fig. 1. SF increases the PV and YPof slurry. It is obvious that YP and GS ofslurries are more affected than PV. SFabsorbs the water in the solution andincreases the gel of the slurry, making astrong network of cement and SF particles.PV is the result of friction between solid tosolid and solid to liquid and liquid viscosity.SF does not increase the viscosity of theliquid phase of the slurry and its sphericalparticle shape acts as a ball bearing betweenthe cement particles[13], hence it does nothave a significant effect on the PV of cementslurry with respect to other rheologicalproperties. Also, 10 sec and 10 min gelstrength of 90 pcf cement slurry are increasedthe same as PV and YP (see Fig. 2).Standard Fluid Loss (FL) and Free Water(FW) of the mentioned cement slurry areshown in Fig. 3. FL of 90 pcf neat cementslurry decreases from 1741 to 537 and 490.7(cc/30min) when 15% and 20% BWOC SFare added to the cement slurry. Note that theFL of 15% and 20% BWOC SF is close47
Shadizadeh, Kholghi, Salehi KassaeiMueller and R.L Dillenbeck[1], 15% BWOCSF has 24 (cc) excess water, but the FW of15% and 20% BWOC SF is zero.together. The mechanism of fluid losscontrolling of SF is bridging and blockingthe pores in the cement cake.Regarding the recommendation of D.T40222018Slurry Density:90 pcfComposition:1. Class G Dyckerhoff cement2. SF35YP, lbf / 100 ft230PV, cp162514201210158106542005101520% BWOC SFFigure 1. Effect of SF on PV and YP of 90 pcf cement slurries.30251210208156410 min Gel Strength, lb/ 100 ft14Slurry Density:90 pcfComposition:1. Class G Dyckerhoff cement2. SF210 sec Gel Strength, lb/ 100 ft2161020505101520% BWOC SFFigure 2. Effect of SF on 10 sec and 10 min Gel Strength of 90 (pcf) cement slurries.48Iranian Journal of Chemical Engineering, Vol. 7, No. 1
Experimental Investigation of Silica Fume as a Cement Extender for Liner Cementing in Iranian Oil/Gas Wells30Slurry Density:90 pcfComposition:1. Class G Dyckerhoff cement2. SF1800251600201400151200101000Free Water at 80 F, %Standard Fluidloss, 5101520% BWOC SFFigure 3. Effect of SF on Standard Fluid loss and Free Water of 90 pcf cement slurries.cement is increased and water permeabilitydecreases drastically. Compressive strengthof set cement is improved by the microfilling effect of silica fume particles and theirpozzolanic reaction.Compressive strength and water permeabilityof 0%, 15% and 20% BWOC SF are shownin Fig. 4. When the 15% and 20% BWOCsilica fume are added to 90 pcf neat cementslurry, the compressive strength of setSlurry Density:90 pcfComposition:1. Class G Dyckerhoff cement2. SFStandardFluid loss,cc/30 0.004010000.00350.00308000.0025600Water Permeability, 5101520% BWOC SFFigure 4. Effect of SF on Compressive Strength and Water Permeability of 90 pcf cement slurries.Iranian Journal of Chemical Engineering, Vol.7, No.149
Shadizadeh, Kholghi, Salehi KassaeiHeight reduction of neat cement inpermeability mold is equal to 5 (mm). 20%height reduction of neat cement slurry in thepermeability mold leads to cement particlesgetting close together, but the heightreduction of 15% and 20% BWOC is zero.Silica fume particles hold the excess water ofthe cement slurry creating a narrow channeland increasing the pores tortuosity of setcement by its small size and pozzolanicreaction. Although 15% and 20% BWOC SFslurries have preferable characteristics, 15%BWOC SF is selected based on economicalconcern. The summary of 15% BWOC SFslurry and set cement properties are shown inTable 4.Table 5 shows the composition number,cement slurry composition, mixing methodand density of the cement slurries thatcontain 15% BWOC silica fume.Table 5.Composition No., cement slurry composition,mixing method and density of 90 pcf and 15% BWOCSF cement slurry.Comp. No.55565758596066676869Table 4. Summary of composition No. 56 properties.Composition No. 562 cc AF ITG Dyckerhoff cement15%BWOC SFMixing methodCompressive Strength (psi)1250PV (cp)1870Wet blended71722YP (lbf/100ft )19.510 sec GS (
according to sections 15.2, 15.3, 15.4.1 and 15.5 of API RP-10B[10]. Cement slurry was conditioned for 35 to 40 min in an atmospheric consistometer to BHCT before the test. According to section 15.4.1 of API RP-10B[10] the graduated cylinder must be immersed in a water bath with a vibration free condition, but in this study, due to lack
Fig.2 Fly Ash Fig. 3 SILICA FUME i. Silica Fume: Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. One of the most beneficial uses for silica fume is in concrete. Because of its chemical and physical properties, it is a very reactive pozzolan. Concrete containing silica
Hootan (1993)3 reported that for silica fume concrete split tensile strength increases only at 28 days. Rao (2003)4 studied effect of silica fume on cement pastes. He observed that consistency of cement increase with increase in silica fume content .Alshamsi et al (1993)5 concluded that addit
and Other Non-Crystalline Forms . CAS Registry Numbers: 7631-86-9 (synthetic amorphous silica) 60676-86-0 (fused) 69012-64-2 (silica fume) 61790-53-2 (uncalcined diatomaceous earth) 112945-52-5 (pyrogenic colloidal silica) 112926-00-8 (precipitated silica and silica gel) Prepared by . Jong-
ASTM C618 25 Slag cement conforming to ASTM C989 50 Silica fume conforming to ASTM C1240 10 Total of fly ash or other pozzolans and silica fume 35 Total of fly ash or other pozzolans, slag cement and silica fume 50 WHAT 0.40, and a minimum specified stren
Jan 23, 2018 · Concrete Mix Design and Mix Design Acceptance under the new 2018 PennDOT ASR Specification. . Silica Fume—Use a quantity of silica fume between 5% and 10%, by weight, of the total cementitious material. Use of silica fume will be allowed on an experiment
Laboratory Fume Hoods Sash Closed Sash Open Sash Closed Sash Open 3 Sash Closed Sash Open Definitions BMC/Laboratory Fume Hoods Exhaust Collar -Connection between exhaust duct and Fume Hood through which all exhaust air passes. Face Velocity -Speed of air moving into Fume Hood entrance or access opening, expressed in feet per minute (FPM).
Fume hoods also provide physical protection against fire, spills, and explosion. Laboratory fume hoods only protect users when they are used properly and are working correctly. A fume hood is designed to protect the user and room occupants from exposure to vapors, aerosols, toxic materials, odorous, and other harmful substances. Fume hoods provide
Fume Hood Controller (FHC) Installation & Mounting Open the controls enclosure on the Antec Controls valve that is installed in the fume hood exhaust duct. Follow the wiring diagram in the project submittals. Required items: 1 Venturi Valve or Venturi FX 2 Fume Hood Controller 3 Fume Hood Interface 4 RJ-45 Plenum Rated FHI Cable, by .
