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A Novel Oil Well Cementing Technology.pdf

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Petroleum Science and Technology, 24:1267–1282, 2006 Copyright © Taylor & Francis Group, LLC ISSN: 1091-6466 print/1532-2459 online DOI: 10.1081/LFT-200056771 A Novel Oil Well Cementing Technology Using Natural Fibers M. M. Al-Darbi Department of Materials Engineering, The University of British Columbia, Vancouver, British Columbia, Canada N. O. Saeed, L. O. Ajijolaiya, and M. R. Islam Department of Civil Engineering, Dalhousie University, Halifax, Nova Scotia, Canada Abstract: In many indust
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  Petroleum Science and Technology , 24:1267–1282, 2006Copyright © Taylor & Francis Group, LLCISSN: 1091-6466 print/1532-2459 onlineDOI: 10.1081/LFT-200056771 A Novel Oil Well Cementing TechnologyUsing Natural Fibers M. M. Al-Darbi Department of Materials Engineering, The University of British Columbia,Vancouver, British Columbia, Canada N. O. Saeed, L. O. Ajijolaiya, and M. R. Islam Department of Civil Engineering, Dalhousie University, Halifax,Nova Scotia, Canada Abstract:  In many industrial processes, the pipeline systems are lined with a protec-tive layer of cement mortar. In petroleum wells, cement slurry is placed in a wellboreto be hardened into an impermeable mass that seals the annulus from fluid flow andprotects the casing from corrosion for the life of the well. When uniform linings of neat cement fail in tension, one or more large cracks are formed and the pressurizingfluid or mud easily flows through the cracks. The necessity to check the damagingeffect of plastic shrinkage in cement mortar, and thus the formation of cracks, hascalled for further studies in this topic. In the past, the most common research topichas been in the areas of polymer fibers that are expensive and environmentally un-acceptable. In the quest of pursuing technologies that are environmentally friendly,inexpensive, and innovative, this paper suggests the use of human hair, a waste ma-terial, in order to replace polymer fibers. Hair waste has been used as a new naturalfiber to reinforce mortar and cement and improve their impermeability. The investi-gation reported herein concerns the effects of human hair fibers on the reduction of shrinkage cracking of mortar. The influence of mix proportions on the plastic shrink-age of human hair fiber reinforced mortar has been studied. The approach selectedin this study is based on the factorial design of experiments, in which the consideredparameters are cement/sand ratio, water/cement ratio, and human hair fibers content.The results show that human hair fibers are effective in reducing the plastic shrinkagecracks area of mortar by a remarkable percentage up to 92%. Keywords:  shrinkage cracking, mortar, human hair waste, petroleum well cementingAddress correspondence to M. M. Al-Darbi, Killam & NSERC Post-Doctoral Fel-low, Department of Materials Engineering, The University of British Columbia, 309-6350 Stores Road, Vancouver, B.C. V6T 1Z4, Canada. E-mail: aldarbi@interchange.ubc.ca 1267  1268 M. M. Al-Darbi et al. INTRODUCTION Cement mortar lining is a process by which metal pipelines are coated inter-nally to protect their structures. There are several advantages of the cementmortar lining of pipes compared to other pipeline protection methods. Someof those advantages are: preventing pipe leakage, protecting the inner surfaceof the pipe against corrosion by forming an alkaline environment in contactwith the pipe material where corrosion of the steel is inhibited, decreasingthe pumping energy consumption by providing a smooth interior surface witha high flow coefficient, and as a result, reducing pipe maintenance.The objective of cementing the annulus, which is present between thecasing and the formation, is to provide zonal isolation of the formationsthat have been penetrated by the wellbore. It has been known for decadesthat cemented annuli in the wellbore are prone to leaks and hence can leadto corrosion (Gollapudi, 1993; Talabani and Islam, 2000). However, no fluidcommunication should develop during the life of the well among these variousformations, whether they are saturated with water, oil, or gas, and the surface(Thiercelin et al., 1998; Nowak and Patout, 1997). When uniform linings of neat cement fail in tension, one or more large cracks are formed and thepressurizing fluid or mud easily flows through them. When fiber containingcement fails in tension, they usually form large numbers of small cracks. Thecement matrix fails first by forming microcracks, and then the fibers take overthe loading. The fiber-laced cracks give a high resistance to fluid leak off.When fiber cement samples are subjected to high impact loads, the cementmatrix shatters, but the fibers hold the broken matrix together (Stewart et al.,1997).In addition, fibers reduce the plastic shrinkage of cement. In the settingprocess, cement slurries shrinkage and that causes the cement hydrostaticpressure to drop. The hydrostatic pressure is important, as gas starts to flowinto the cement when the pressure of the cement column falls below thatof a gas-bearing formation. After the gas has entered the pore system of thecement, the gas inside may overcome the tensile strength of the cement struc-ture, break the cement matrix, and migrate through the microfractures. A lowshrinkage rate is preferable because the decline in the resulting hydrostaticpressure will be slower than that for slurry with a higher shrinkage rate. Slowshrinkage has two advantages: (a) the pressure equilibrium between forma-tion and slurry columns can be reached, and (b) the driving force behind theflow of pore fluid into the cement will be lower. Both factors should reducethe risk of early time gas migration (Backe et al., 2001, 1999; Sabins andWiggins, 1997).The cement sheath integrity is important for safe and economical opera-tion of gas storage, geothermal and producing wells. Loss of cement integritycan cause the following serious events: loss of gas reserves, unsafe operations,premature water of gas cap production, extra costs because of unplanned re-medial operations, and well shutdown (Bybee, 2002).  A Novel Oil Well Cementing Technology 1269 Plastic shrinkage cracks are random cracks that occur in the exposedsurface of fresh mortar during the first few hours after the mortar is placed,while the mortar is still plastic and before attaining any significant strength(Shaeles and Hover, 1988; Samman et al., 1996). As drying starts, the mortarnear the surface dries and shrinks faster than the inner mortar, causing tensilestress and possible cracks. Plastic shrinkage cracking is usually associatedwith hot-weather concreting; however, it can occur within ambient conditionsthat produce rapid evaporation of moisture from the mortar surface (Kosmatkaet al., 1995).Cement and mortar products are notable for their weakness in tensionand for their lack of toughness, which gives risk to frequent cracking underimpact loads, thermal shocks, or dimensional changes due to humidity vari-ation. Fibers have been used for decades to overcome such deficiencies andto improve the impermeability and minimize shrinkage, which are essentialrequirement properties of concrete besides its strength. The three main typesof fibers that may be used as reinforcement for concrete are steel, glass, andorganic (natural and synthetic) fibers. As far as natural fibers are concerned,animal and vegetable fibers (i.e., wood-cellulose, sisal, bast, coconut, andbagasse) are all being used in various sheet materials (Padron and Zollo,1990; Krenchel and Jensen, 1980; Majumdar and Nurse, 1978). The draw-backs of using these natural materials are: the high water absorption whichmust be allowed for in the mixing process, the biological deterioration of thefiber if not treated, and the strength loss that may occur in alkaline environ-ments. Additional processing may be required, as in the case of bagasse, toremove the sugar from the fiber (Soroushian and Ravanbakhsh, 1998; Cook,1980).In this paper, human hair waste is introduced as a new mortar-reinforcingmaterial. It would be highly pertinent to talk about the hair morphology, me-chanical, chemical, physical, and electrical characteristics, to elucidate andprovide the reader with the unique characteristics of hair that make it poten-tially usable as a composite in cement matrix. Human hair consists of fivedefinite morphological components: cuticle, cortex, medulla, melanin gran-ules, and cell membrane complex, each distinct in morphology and chemicalcomposition. Human hair consists of approximately 80% protein, 15% water,and 5% lipids. The water content of hair varies directly with the ambientrelative humidity (Potsch, 1995).Regarding the hair mechanical properties, the load required to obtainbreakage of a natural and healthy hair varies between 50 and 100 g. Theaverage healthy human head, which contains approximately 120,000 hairs,may handle 12 metric tons (Katz and Chatt, 1988). For an average hair, thedistribution point corresponds to a load of 12 kg/mm 2 , and this exceeds that of aluminum. The unusual hair strength is caused by the keratin, which is a typeof protein found in the hair cortex. The long keratin molecules in the cortexare compressed to form a regular structure, which is not only strong but alsoflexible. Keratin is unique in that its chains contain high concentrations of a  1270 M. M. Al-Darbi et al. particular amino acid called cystine. Every cystine unit contains two cystineamino acids in different chains that have come to lie near to each other andare linked together by two sulfur atoms, forming a very strong chemical bondknown as a disulphide linkage. Many disulphide bonds form down the lengthof the keratin chains, joining them together like the rungs of a ladder (Gray,2000).Hair has a high frictional coefficient, higher than that of vegetable orsynthetic fibers. The high frictional coefficient of hair is attributed to itsspecial surface structure (presence of scales), as can be seen in Figure 1(Katz and Chatt, 1988). Hair is permeable to water in liquid form as well asto water vapor. After sufficient contact, hair keratin can absorb water up to35 or 40% of its weight. The absorbed water is partially linked to the keratinprotein by hydrogen bonds, but it can also exist in the free form. When wateris absorbed by keratin the hair diameter can increase by 15–20% and itslength can increase only by 0.5–2%. The water absorption and subsequentswelling depends mainly on the pH level. Swelling is limited if the pH islow, and greatly enhanced if the pH is high (Zviak, 1986).It was found recently that human hair is a good absorbent material. Forinstance, in 1998 the US EPA’s (Environmental Protection Agency) Oil SpillProgram Internal Journal published an astonishing report on hair as a goodabsorbent material for crude oil spill clean up. It was reported therein thatNASA (the National Aeronautical and Space Administration) was testing anunusual absorbent material for oil spill clean up with human hair, after a  Figure 1.  Scanning electron microscope (SEM) photomicrograph for a human hairfiber.
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