synopsisA process for preparing metallic cobalt particles of uniform size in the 10-1000 A. range is described. Dicobalt octacarbonyl is thermally decomposed in solutions of dispersant polymers to form stable colloids of discrete particles which are separated by polymer coatings. Variation of polymer composition, molecular weight, and solvent used results in a variation of particle size and colloid stability. Preparation of single-domain ferromagnetic cobalt particles with good magnetic properties depends on a very delicate balance between dispersant polymer, solvent, and the growing metal particle. A number of addition and condensation polymers can act as dispersants. The most successful are linear addition polymers of high molecular weight having relatively nonpolar backbones. Ideally, groups with a polarity greater than the backbone are attached at intervals of at least 100 but not more than 200 backbone atoms. The need for more polar groups and their spacing becomes less critical with increasing polymer molecular weight. The polymers appear to stabilize the metal particles by adsorption to form a thick film which s e p arates the particles sufficiently to keep van der Waals energy of attraction below thermal energy levels. The solvent must solubilize the polymer coating sufficiently to allow the particle to grow. It should be less polar than the most polar group in the polymer and be chemically inert.

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The recent letter by Skinner' draws attention to two features of capillary rheometry which are not often appreciated in routine viscometric meauurements. One of thebe effects has received considerable attention in these labor5 tories in connection with the flow of molten polypropylene and the establishing of a melt flow index test method for that material.2 Skinner shows that with the standard melt indexer there may be a 50% increase in flow rate during the complete extrusion of a full charge of polythene, assuming a power law of flow, and making no capillary end connection. It is, of course, a prerequisite that for a standardized test method, the measured quantity shall respond to the test conditions in the same way for all materials tested-in this case that the flow rate shall be constant at all points during the extrusion. It is clear from Skinner's example, that this is not true in the case quoted: whether or not this has been experimentally observed durin? routine measurements of melt index in the United States or Canada is not known but as the ASTM test method requires only one sample of extrudate to be cut, it is unlikely that changes in rate would be noticed: on the other hand, the B.S.I. method inrludes, in its proccdure, a check on the constancy of flow rate.With polypropylene, the position becomes much worse, for the index n may be as much as 2.5, and the consequent increase in flow rate is by a factor of 3.6 in the course of a run. It was the direct observation of such an increase that initiated work on this problem, which showed that the pressure gradient in the barrel, or "reservoir effect," was responsible.Oakes and Peover in 1946 and Clegg in 19578 convidered the Melt Indexer as a system of two extruders in series, and showed that the barrel pressure gradient was only of the order of a few percent for most polythenes at grading stress (1.7 X 106 dynes/cm.*). Clegg showed, however, that for materials with n > 2 (e.g., P.V.C.) the effect was very great, and could not be ignored in the measurement of melt indices.His treatment gives an expression for the output rate:where L = length of polymer column between die and piston, 1 = length of die, r = radius of die, R = radius of barrel, and n = flow power law exponent. This result can also be derived from the equation given by Skinner.In the Melt Indexer, with n = 2, Q increases by 100% between the beginnin% and end of the run, and attains the value equivalent to that due to the whole pressure on the piston only at the end of the run.Measurements of the pressure in the melt near the die entry were made (a) by the deflection of a diaphragm in the barrel wall2 and later ( b ) by a pressure transducer in a similar location (Lamb and Benbow*). A parallel register of the rate of flow was also made and both showed an increase as the piston descended. Values of apparent viscosity calcylated from the rate alone and assuming full pressure to be operative at the die entry showed a decrease by a factor of 2 in the course of the run, whereas those using the pressure...

The chemical process described here has proved to be an effective method of preventing fluid movement out of or into a wellbore. This process provides a strong, durable plug at normal formation temperatures as well as under steam injection conditions where most plugging methods fail. Introduction Control of fluid movement, from the wellbore into earthen formations or from the formation into the wellbore, is a universal problem in the oil industry. Injection profile control is an integral part of most assisted recovery or steam stimulation programs. Premature entry of water or gas into the producing Premature entry of water or gas into the producing wellbore in both primary and assisted recovery operations also creates many problems. Numerous mechanical, physical, and chemical techniques have been used to try to overcome these problems. The most commonly used technique is cement problems. The most commonly used technique is cement squeezing, a method that is much less effective than generally recognized. Cement, a particulate material that cannot penetrate formation matrix to any great depth, forms a filter cake on the formation face that often breaks down under pressure. Mechanical packers are used to isolate zones in a wellbore. packers are used to isolate zones in a wellbore. This technique is effective if the wellbore is cased and good cement bonding exists between the casing and formation. Lost circulation materials are often used to form a filter cake, which impedes fluid flow into thief zones; for the most part, noted improvements are temporary. A number of chemical processes for plugging or reducing formation permeability are commercially available. These processes range from pumping two chemical solutions into the formation to mix and form an insoluble precipitate to using relatively sophisticated polymer systems that are chemically activated prior to pumping into the matrix where they set up at a later time to form a gel or solid that plugs and reduces permeability. All are based on true solutions that can be pumped through matrix. The success of these techniques depends on the formation being treated (matrix or fracture plugging, carbonate content, etc.), volume of chemical used (large volume treatments are recommended with gel-forming systems to assure coverage), and the precautions taken to assure proper fluid placement. None of the commercial processes proper fluid placement. None of the commercial processes are recommended for steam injection wells. We have developed a chemical method for permanent formation plugging that has a number of permanent formation plugging that has a number of advantages over commercially available processes. In the following pages the process, process fluids, laboratory development, and field applications are summarized and discussed. Process Description Process Description This new process is based on the acid-catalyzed polymerization of furfuryl alcohol resins. It is polymerization of furfuryl alcohol resins. It is applied by injecting an acidic solution into the interval to be plugged, followed by the resin solution. The two solutions mix in the formation to start a rapid, vigorous, exothermic reaction forming a hard solid that fills the pore space (or fracture). JPT P. 559

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