The cement covered by this specification is suitable for use in shrinkage-compensating concrete and shall be designated as Type E-1. for completion or for remedial operations, Compositions for cementing, e.g. ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SPANGLE, LLOYD B.;REEL/FRAME:004948/0070, Free format text: method for placing a seal, plug or fitting in a well. Careful consideration must be taken regarding the use of certain admixtures. The performance of these accelerators depends on the cement chemical composition and fineness, and the presence of mineral additions such as flyash, and blastfurnace slag. 15. of deionized water with 20 ml. Expansive cement shall conform to the requirements as to chemical composition prescribed. Further, the BET surface area of the particles is preferably between about 0.8 to about 1.8 m. 1. In such a particle size range, the 14 day expansions are increased dramatically over what would be expected, based upon the increased proportion of magnesium oxide present. No. 12, R. S. Gordon and W. D. Kingery. However, this may be a result of the fact that, as shown in Table 1A, the magnesium oxide used in Trial 11 has a larger number of particles which are smaller than 38 microns in diameter. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this … Cement: Cement is the mixture of calcareous, siliceous, argillaceous and other substances. trays. Chemical composition of pozzolana cement is: Silicon Dioxide 21%, Al2O3 2.59%, SO3 2.41 … 1. An expansive cement composition made of argillaceous and calcareous materials and containing from about 1 to about 70% by weight thereof of free CaO and from about 2 to about 7% by weight thereof of MgO uniformly distributed therein, with the remaining portion of said materials being primarily tricalcium silicate … When the calcining temperature and time are carefully controlled within the ranges above, and the particle size of the magnesium hydroxide starting material is also controlled, it is possible to obtain a resulting magnesium oxide product which has particle sizes, a BET surface area, and an acid neutralization time within the parameters specified above, without any further processing of the magnesium oxide being required. The composition is particularly useful for cementing a casing in place in a bore of an oil, gas, or other well, which may experience at some point in time a relatively high bottom hole static temperature(BHST). However, there is no indication as to the amount of magnesium required, nor is there any indication as to the size or surface area of the magnesium oxide particles. 4. Fineness of Cement. The slurries were allowed to hydrate to a hardened state at 200° F. (93° C.), and some also at 300° F. (149° C.) All of the foregoing variables, other than particle size, are tabulated in Table 5. %) given for all of the trials described below are based upon the weight of dry cement present(BWOC), unless otherwise indicated. 22. In the process for making the composites, the concrete is allowed to cure at about 159° C. to 200° C. under 6 to 15 atmospheres pressure. Furthermore, there is disclosed a method for cementing a casing in a bore of a well, which comprises placing a cement slurry composition of the foregoing type between the casing and the bore. At temperatures higher than 160° C., magnesium oxide calcined at 1600° C. is suggested as an expanding additive. A well-known practice in oil, gas, or other wells, which have a bore penetrating a number of earth formations, is to cement a steel casing in place within the bore by placing cement slurry between the steel casing and the bore walls. U.S. Pat. 2. Tests were apparently conducted with magnesium oxide calcined at up to 950° C. Neither particle size nor surface area of the magnesium oxide, was controlled in any of the test results disclosed in that paper. ;ASSIGNOR:SPANGLE, LLOYD B.;REEL/FRAME:004948/0070, Owner name: The expansions were 0.68 and 0.80% for the initial and final mix specimens, respectively (both from an average of two measurements). … A method as defined in claim 14 wherein the BET surface area of the particles is between about 0.8 to about 1.8 m. 16. Expansive Cement. Under conditions of restrained expansion, cements such as those of Trial 9, would be expected to exhibit good compressive strengths. The expansion mechanism is the expansion of ettringite generated in cement paste. added 1N. No. Such situation may allow undesirable fluid (which term includes liquids and gasses) communication between different formation zones penetrated by the bore, or even allow fluids produced from certain zones to undesirably leak to the surface. All expansions were measured with the cement exposed to a temperature of 200° F. (93° C.) for 7 and 14 days. An expandable cement composition as defined in claim 5, wherein the magnesium oxide has been calcined at between about 1150° C. and about 1250° C. 7. Without watering, type G additives promote larger total longitudinal expansion. One known expansive agent comprises calcium sulfate. A method as defined in claim 18 wherein the bottom hole static temperature of the well is between about 70° C. and about 290° during placement of the cement. Furthermore, for practical reasons, it will often be desirable that the expansion in the set cement must be at a practical rate under the temperature and other conditions to which it is to be exposed in use. To ascertain the effectiveness of cements using magnesium oxide of the type described, as an expansive agent, a field trial was conducted in which a steel casing was cemented in place within the wellbore of an oil well. The composition is reacted in a conventional cement kiln at a temperature range of 2500° F. to about 2900° F., which the patent indicates will inherently cause the magnesium oxide to "become diffused throughout the composition in the form of very fine crystallites of crystals of periclase, the vast majority of which have a size no greater than about 10 microns." However it is apparent from those Trials and Trials 1-3, that not only must the ANT, and hence surface area, be controlled, but also that the particle size range must also be controlled, as already shown by Table 3. The expansive agent must be designed such that, at the temperature to which the liquid cement will be exposed, it does not attempt to produce most of its expansive effect while the cement is still liquid. The foregoing article deals primarily with the use of calcium oxide typically calcined at between about 850° C. and about 1400° C., as an expansive agent in amounts of between 7 and 15 percent (%). It will be seen, that none of the above references teach or suggest an expansive cement composition of the present invention, which is useful for cementing a casing within the wellbore of an oil, gas or other well, and contains as an expansive agent, magnesium oxide calcined at 1100° C. to 1500° C., at least 50% of the particles of which have a diameter of greater than 30 microns, and which has a surface area of about 0.8 to about 1.8 m2 /g. PPC or Portland Pozzolana Cement: Pozzolana is a type of volcanic ash that is used for mortar, concrete, and plaster purposes. The cement used may include a Portland cement, a high aluminate cement, or a gypsum cement, or any other hydraulic cementitious material such as type C fly ash. This magnesium oxide had an ANT of 26.4 minutes and a BET surface area of 0.82 m2 /g. The foregoing does not appear to be the case though, for the results of Trial 11 at 300° F. (149° C.) versus those of Trial 13 at the same temperature. added 1N. An expandable cement composition as defined in claim 3, wherein a sufficient amount of magnesium oxide is present to produce an expansion in the set cement composition of at least about 0.5% when the set composition is exposed to at least one temperature which is within the range of about 200° C. to about 500° C. 5. An expandable cement composition as defined in claim 7 wherein the acid neutralization time of 1 g of the magnesium oxide in 60 ml. (1) Type K expansive cement — a mixture of portland cement, anhydrous tetracalcium trialuminate sulfate (C 4 A 3 S), calcium sulfate … It should be noted that the crystallite size, is distinct from the particle size which is indicated by sieving, since it was evident from the SEM studies that the particles of magnesium oxide were made up of individual smaller particles (referred to as crystallites) fused together. A method as defined in claim 15 wherein the acid neutralization time of 1 g of the magnesium oxide in 60 ml. 9. 1, with those of Trial 12 (all having almost identical calcination temperatures and times), a larger proportion of particles below 40 microns in size, tends to result in substantially reduced expansion at 300° F. (149° C.). 11, pages 10-13, November, 1973. % magnesium oxide was used. Rapid Hardening Cement. By "net expansion", or simply "expansion" of a cement, is meant that the unrestrained set cement will exhibit a volume increase over its liquid (i.e. Specimens of the mixed cement composition were taken from both the initial field mix, and the final field mix, prior to pumping down the well. These samples were checked for BET surface area using a MICROMERITICS FLOW SORB II 2300 (rapid surface area instrument). 8 (Aug. 1, 1951); "Relations Among Particle Size, Shape, and Surface Area of Mg(OH)2 and Its Calcination Product", by V. A. Phillips et al., Journal of the American Ceramic Society, V. 61 No. An expandable cement composition useful for cementing a well casing within the bore of a well, comprising: 4. MEHTA et al. Thus, from the general trend discussed in connection with Table 4 and reviewing the 300° F. (149° C.) expansions in Table 2, it appears that the best expansions are obtained with magnesium oxide samples having ANTs somewhere between about 20 to 30 minutes. in "Magnesium Oxide Additive For Producing Self Stress in Mass Concrete", 7th International Congress on the Chemistry of Cement, Paris 1980, Volume III, pages v-6,9. 10. %'s as expansive agents in expansive cement slurry compositions consisting of 793 grams PERMANENTE Class G cement, 0.3% lignosulfonate retarder, 0.5% bentonite and 44% water. Not only would the compressive strength of such cement compositions not decrease under restrained conditions with such temperature variations, it would in fact be expected to increase. Table 1A identifies the calcining temperature and duration of calcination at that temperature(often referred to herein as simply the "calcining time"), for each sample, as well as the corresponding trial number in Table 2 in which it was used as an expansive agent. Each slurry in these trials consisted of MARYNEAL LONE STAR Class H cement, 40 wt.% silica flour, 0.5 wt.% of a lignin sulfonate retarder, and 50 wt.% water, plus varying weight percentages of different magnesium oxide samples as described in Table I below. Such can occur for example in geothermal wells or wells exposed to heat from fire flooding procedures. Another paper of relevance in disclosing large numbers of attempts to produce expansive cements utilizing various additives, is that by W. Kurdowski, entitled "Expansive Cements", 7th International Congress on the Chemistry of Cement, Paris 1980, Vol I, pages v-2/1 to v-2/11. It has now been discovered that cement compositions with consistently high rates of unrestrained linear expansion and good compressive strengths can be obtained by using magnesium oxide as an expansive agent in the composition. U.S. Pat. That is, an expansion was obtained in Trial 3 (MgO calcined at 1200° C.) which was better than that obtained in Trial 5 (MgO calcined at 1000° C.), by an amount of about 300% at 93° C., and about 30% at 149° C., even though the concentration of magnesium oxide in Trial 3 was about 25% less than that in Trial -5. A method as defined in claim 10 wherein the hydratable cement of the cement slurry composition is a Portland cement. 7TH INTERNATIONAL CONGRESS ON THE CHEMISTRY OF CEMENT. Definition: a cement that when mixed with water produces a paste that after setting increases in volume to a greater degree than does portland-cement paste. Also, the same magnesium oxide was used in the Trials 2, 4, and 6 of Table 9 below, as was used in Trial 8 of Table 2 above. added 1 N. acetic acid, is between about 17 to about 25 minutes. There is no discussion in the patent on the affect of calcining magnesium oxide at various temperatures, nor the affect of particle size or surface area of magnesium oxide. of deionized water with 20 ml. To illustrate the foregoing, a cement slurry was prepared using PERMANENTE Class G cement, 35 wt. An expandable cement composition as defined in claim 4, wherein 80% of the magnesium oxide particles have a diameter of between about 150 to about 400 microns, and wherein the magnesium oxide particles have a BET surface area of between about 1 and about 2 m. 6. This latter feature allows magnesium oxide to be produced with particles of the required size and surface area, without the necessity of regrinding the particles. for killing wells, Compositions for cementing, e.g. Thanks! % of magnesium oxide. Expandable cement compositions using such magnesium oxide, and a method of using them in cementing of wells, are also disclosed. It will be seen from Table 7B then, that the horizontally restrained compressive strength is always higher than the unrestrained compressive strength. Likewise, it will be seen that the expansions produced after 14 days in Trial 2 (MgO calcined at 1200° C.) are significantly greater than the expansions produced in Trial 4 (MgO calcined at 1000° C.) even though in Trial 2 the magnesium oxide concentration is one-half that present in Trial 4. It has been discovered that this may be accomplished by providing an expansive agent in the cement, which agent will produce most of its expansion only upon the later raising of the BHST. One is designed to expand and compensate for the shrinkage which occurs in conventional portland cement concrete as it hardens. Compensate for the shrinkage losses for mortars, concrete or artificial stone, e.g Trial! 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