Barite abrasion

Zinc oxide (ZnO) is widely used as an active filler in rubber and as a weatherability improver in polyolefins and polyesters. Titanium dioxide (TiOj) is widely used as a white pigment and as a weatherability improver in many polymers. Ground barites (BaS04) yield x-ray-opaque plastics with controlled densities. The addition of finely divided calcined alumina or silicon carbide produces abrasive composites. Zirconia, zirconium silicate, and iron oxide, which have specific gravities greater than 4.5, are used to produce plastics with controlled high densities. 

Solid Phases. The commonest weighting agent is barite, which, in its pure form, has a density of 4500 kg/m3. The American Petroleum Institute (API) specification (12) for the density of barite is that it must be at least 4200 kg/m3. Other API specifications are the soluble alkaline metal concentrations must not exceed 250 ppm and a maximum of only 3 wt% of the barite must have a particle size in excess of 75 pm with a maximum of 30 wt% having a particle size of less than 6 m. Other suspended weighting agents are calcium carbonate and iron oxide [hematite (12)], although iron oxide is not often used due to its abrasiveness. 

Since the 1940 s, barite has been the most dominant material for weighting muds. The reasons are Its fairly high specific gravity, low abrasiveness, usefulness as inert material in both water-base and oil-base muds, and the availability at a low cost. 

The results of rheological and filtration properties are presented in Table 2 for all mud types. It is apparent from the results that a treated or untreated Itabirite mud systems has better rheological characteristics than a barite mud system (untreated or treated). This is due to the fewer inert solid particles in the itabirite mud system that cause less mechanical interaction and electro-chemical attraction between the active particles. With the addition of polymer at each concentration, lower PV and YP can be obtained with the Itabirite mud system than with barite. Therefore, the use of polymers In the Itabirite mud system were more compatible than in the barite mud. This advantage would enable the itabirite mud system to be tested with an even higher polymer concentration, overcoming the abrasion problem in the mud system. 

Resulting weight losses of mud types B, IL, IM, and IS with no polymer concentration (untreated mud. Table 3) indicated that the selected ranges of particle size of itabirite did not lower the abrasiveness to the barite level, but a more acceptable level of abrasion appeared. Itabirite particle sizes between 37 and 44 microns showed more than 55% lower abrasion compared to the particle sizes between 74 and 125 microns. In addition, ranges of particle size of itabirite between 44 and 74 microns showed more than 43% lower abrasion compared to particle sizes between 74 and 125 microns. Abrasiveness was seen to have a similar dependence on the particle size distribution In a mud system. The smaller the solid particle sizes contained within the mud of the same density, the less abrasive it was. 

In this study, Drispac Superlo or Kelzan XCD polymer with concentration of 0.25, 0.5, and 0.75 Ibm/bbI were used as coating agents for the purpose of lowering the abrasiveness. It is apparent from the results (Table 3) that 0.75 Ibm/bbI concentration of DS or KXCD for large particle sizes (74-125 microns) and 0.5 Ibm/bbI for small particle sizes (37-44 microns) were adequate for lowering the abrasivity of the itabirite mud system to the barite level. 

Fillers, generally inorganic materials such as calcium carbonate, barite, silicate, kaolin, or china clay, are used primarily to lower costs and also to impart special properties such as hardness, abrasion resistance, and no sticking. 

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