Oil-well cement

Retarders and Accelerators. Materials that control hardening of cement may be either organic or inorganic. Retarders are often incorporated in oil well cementing and hot-weather concrete appHcations, whereas accelerators may be useful for cold-weather concrete appHcations in which higher rates of reactivity are desirable. In most cases, these admixtures are used in low concentrations, suggesting that they act by adsorption. 

Oil well cements are manufactured similarly to ordinary Portland cements except that the goal is usually sluggish reactivity. Eor this reason, levels of C A, C S, and alkafl sulfates are kept low. Hydration-retarding additives are also employed. 

Oil well cements (78) are usually made from Pordand cement clinker and may also be blended cements. The American Petroleum Institute Specification for Materials and Testing for Well Cements API Specification 10) (78) includes requirements for nine classes of oil well cements. They are specially produced for cementing the steel casing of gas and oil wells to the walls of the bore-hole and to seal porous formations (79). Under these high temperature and pressure conditions ordinary Pordand cements would not dow propedy and would set prematurely. Oil well cements are more coarsely ground than normal, and contain special retarding admixtures. 

There are two basic oil well cementing activities primary cementing and secondary cementing. 

API Standard lOA API Specifications for Oil-Well Cements and Cement Additives, April 1969. 

A terpolymer fonned from ionic monomers AMPS, sodium vinyl sulfonate or vinylbenzene sulfonate itaconic acid, and a nonionic monomer, for example, acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, N-vinyl acetamide, and dimethylaminoethyl methacrylate, is used as a fluid loss agent in oil well cements [1562], The terpolymer should have a molecular weight between 200,000and 1,000,000 Daltons. The terpolymer comprises AMPS, acrylamide, and itaconic acid. Such copolymers also serve in drilling fluids [1892]. 

Lignin amines with high nitrogen content are water soluble at both alkaline and acidic pH values. The lignin amines have various useful properties. For example, they are active as flocculants, filtration aids, scale inhibitors, fluid loss additives, oil well cement additives, and corrosion inhibitors among other potential uses. The nitrogen is introduced into the lignins with the Mannich reaction [1570]. 

Silica powder has been studied as a stabilizer for oil well cement at high temperatures [1895]. Tests indicated that silica powder can improve the stability and pressure resistance strength of cement. The manufacture of very-high-strength concrete (after 28 days the compressive strength is greater than... 

J. F. Baret and P. Drecq. Dispersant for oil-well cement slurries and corresponding slurries (dispersant pour laitiers de ciment petroliers et laitiers correspondants). Patent FR 2622572, 1989. 

S. C. Crema, C. H. Kucera, G. Konrad, and H. Hartmann. Fluid loss control additives for oil well cementing compositions. Patent US 5025040, 1991. 

S. Gopalkirshnan and M. Roznowski. Additive composition for oil well cementing formulations. Patent US 5258072, 1993. 

Y. Zhang and L. Chen. High temperature stabUizer for oil well cement. Drilling Fluid Completion Fluid, 10(3) 58-61,75-76, May 1993. 

Oil-well acidizing, use of aqueous hydrochloric acid in, 73 834 Oil well cement retarders, lignosulfonates as, 75 18... 

Oil-well cements, 5 493, 500t, 502 U.S. shipments, 5 498t Oil wells, cyclic steam stimulation of, 73 619... 

Typical uses include the production of non-dispersible underwater concrete and reduction of the accumulation of bleed water in mass concrete placed in deep forms. Consequently, AWAs are useful in mass concrete work because they prevent the formation of laitance on the surface of the concrete and thereby reduce the excessive cleaning between successive lifts. The admixtures also reduce the voids formed under horizontal reinforcing bars. Therefore, bond to steel increases and potential corrosion problems are reduced. The admixtures are also used in conjunction with WRAs in oil-well cementing grouts to reduce pipeline friction and rapid water loss and grouting of pre- and post-tensioned concrete ducts [47]. New valves and control devices under development in Europe and Japan used in conjunction with AWA will likely advance the field on underwater concrete. 

Oil well cement is designed to withstand high pressure and temperature of the oil wells. 

The conveying characteristics for the oil well cement conveyed through the steel pipeline are presented in Fig. 15. Once again as wide a range of conveying conditions were investigated as possible. Similar sets of conveying characteristics were obtained for the barytes in the steel pipeline and for both materials in the rubber hose pipeline. The rubber hose was rated to a lObar capability. 

Chapter 9), and this is probably today a more usual solution. The specialized requirements of oil well cements are discussed in Section 11.8. 

Fig. 5.4 (A.B) Types I and II C-S-H, respectively (SEM of fracture surfaces courtesy K. L. Scrivener). (C,D) SEM/STEM pair of ion beam thinned section, showing Type III C-S-H (top, right) and Type IV C-S-H (top, left and bottom, right Jennings et al. (HO)). (A) is of an ordinary Portland cement paste, w/c = 0.5, aged 10 h. (B) is of a paste of an oil well cement, w/c = 0.44, with 2.4% of CaClj on the weight of cement, aged 1 day. (C) and (D) are of a CjS paste, w c = 0.47, aged 330 days.

In oil well cementing (R61,D46,S106) a cement slurry is pumped down the steel casing of the well and up the annular space between it and the... 

Following these two surveys, we conducted a literature review based upon Ceramic Abstracts for the years 1988-2002. The results are summarized in Table 2.1. The results presented in Table 2.1 indicate that there has been a significant increase in the literature on CBPCs in recent years. The major thrust of the research has been in biomaterials and dental cements. Though small in number, there have been several articles in structural materials applications, which also include oil well cements. Interest in conventional refractory materials has continued, and as expected, all the applications have been supported by research in materials structure and properties of the CBPCs. 

In addition to sand, the most important bulk additive in CBPC is fly ash. As we shall see in Chapter 14, fly ash is not just a filler it seems to participate in the chemical reaction that forms CBPCs. As a result, the CBPC products containing fly ash have considerably better mechanical properties and provide a dense structure to the body of the ceramic. Therefore, fly ash has been a major ingredient in products in CBPC construction materials and oil well cements. 

Precalcination reduces the rate of dissolution of MgO substantially, and as we shall see later in this chapter, a slurry of MgO and H3PO4 or an acid phosphate can be mixed for several minutes before the exothermic acid-base reaction kicks off. Often, large-scale production of ceramics, such as oil well cements, requires hours of pumping time (see Chapter 15) or long setting times. Even in a production line of refractories that produce castables of consistent quality, the reaction slurry must have a storage life of a few hours. In such cases, chemicals are added to retard the reactions in the slurry. 

Delayed setting time (h) Boric acid 1-7 6h Structural ceramics, oil well cements, waste encapsulation... 

Volume change during setting Most fillers Shght expansion Shght contraction Architectural moldings, oil well cements... 

CBS formulations produce very dense cements, and as we shall see below, the permeability of hardened CBS is always an order of magnitude lower than that of conventional oil-well cements. This characteristic indicates that CBPCs make an excellent sealant against gas migration. 

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