Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1994-10-06
1995-12-12
Willis, Davis L.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
25033908, G01N 2135, G01N 3338
Patent
active
054752205
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns the analysis of samples of neat cement and blends containing a cement component. In particular, the analysis provides a method with which to quantify the various mineral phases in such samples, and is applicable to dry powdered samples of cements such as might be used in the construction industry or oil well operations.
2. Description of the Related Art
Oil-well cementing operations are either "primary", done in the course of drilling a well, or "secondary" or "remedial", intended to remedy deficiencies in primary cementing or alter the well completion for production. During a "primary" cementing process, a cement slurry is pumped down the steel casing and up the annulus between the casing and the surrounding rock formation. The cement slurry must remain sufficiently mobile for the pumping operation to be completed. After it has been placed in the annulus, the cement hardens to form a hydraulic seal in the wellbore, preventing the migration of formation fluids in the annulus. The set cement sheath provides support to the casing string and protects the casing against corrosion by formation fluids. Examples of "secondary" or "remedial" cementing processes are "squeeze" cementing, during which a cement slurry is forced through holes or splits in the casing into voids or a porous rock formation and "plug" cementing, during which a relatively small volume of cement slurry is placed in the wellbore in order to prevent the loss of drilling fluid during the drilling phase or to seal off a depleted zone during the production phase.
The basic ingredient in current cement compositions is portland cement. The raw ingredients of portland cement are lime (CaO), silica (SiO.sub.2), alumina (Al.sub.2 O.sub.3) and iron oxide (Fe.sub.2 O.sub.3). Lime is obtained from calcareous rock deposits and industrial alkali waste products. Silica, alumina and iron oxide are derived from argillaceous materials such as clays, shales and marls and from artificial sources such as blast furnace slag or fly-ash waste from coal-fired power stations. The diversity of raw materials used to manufacture cements contributes to the wide range of composition of the final products. A pulverised blend of the raw materials is fed into a rotating kiln where temperatures as high as 1500.degree. C. produce a molten mixture; subsequent cooling induces a complex series of reactions to produce the four principal mineral phases: "Alite" which is a tricalcium silicate, Ca.sub.3 SiO.sub.5 (commonly abbreviated to C.sub.3 S, which devotes three moles of CAO and one mole of SiO.sub.2); "Belite" which is a dicalcium silicate, Ca.sub.2 SiO.sub.4 (C.sub.2 S); "Aluminate" which is tricalcium aluminate, Ca.sub. 3 Al.sub.2 O.sub.6 (C.sub.3 A); and "Ferrite" which is tetracalcium aluminoferrite, Ca.sub.4 Al.sub.2 Fe.sub.2 O.sub.10 (C.sub.4 AF). These four principal mineral phases leave the kiln as a "clinker" which is subsequently ground with gypsum CaSO.sub.4.2H.sub.2 O to produce the finished portland cement product.
The finished portland cement product may contain a variety of sulphate minerals which are produced during the manufacturing process. The added gypsum may dehydrate to bassanite and/or anhydrite during grinding, and it may also react with alkali sulphate to produce syngenite. The concentration and form of the minor sulphate and hydroxide/carbonate components of a cement may have a considerable effect on the slurry performance. For example, the presence of syngenite in oil well cement may cause premature or "false" setting of the slurry.
Specifications for oil-well cements have been established by the American Petroleum Institute (API). There are currently eight classes of API Portland cement, designated Class A through to H which are classified according to the depths to which they are placed, and the temperatures and pressures to which they am exposed. The main chemical criterion for classifying Portland cements is the relative distribution of the four main clinker phases, kno
REFERENCES:
patent: 4801445 (1989-01-01), Fukui et al.
Fletcher Philip
Hughes Trevor L.
Jones Timothy G. J.
Hanig Richard
Kanak Wayne I.
Lee Peter Y.
Schlumberger Technology Corporation
Willis Davis L.
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