A novel inorganic compound has been developed that combines with dispersed bentonite producing a fluid which exhibits unusual shale inhibition, solids suspension, and contamination resistance. Laboratory and field test data are discussed.
over the last several years a great deal of research has been done in the area of mixed metal layered hydroxide chemistry. Until recently, the bulk of the efforts were fundamental in nature. Recent endeavors have become more applications oriented. The work that is described here is the result of this research effort, utilizing a compound that was engineered to produce the properties described below .
STRUCTURE AND CHEMISTRY
Mixed metal layered hydroxide compounds (MMLHC) are inorganic materials which are made up of discreet layers, consisting of two or more metal ions surrounded by hydroxide ions. Due to symmetry considerations, there is not enough room in the unit cell to accommodate a stoichiometric number of hydroxide ions. Thus, the sheets are electron deficient and a crystallographic positive charge is generated, Figure 1. Because the positive charge must be balanced by anions in order to achieve electrical neutrality, anions associate with the basal plane of the crystallites. The surface interacts with these anions through an ion exchange mechanism, similar to that of anion exchange resin or clay mineral.
The MMLHC that is being utilized in this application consists of very small particles having dimensions of approximately 0.05 microns in diameter by approximately 0.0008 microns thick. Thus when dispersed, the particles are smaller than an average bentonite particle. Due to their particle size and positive charge density, the particles are capable of interacting with cation exchangers such as sodium bentonite through an ion exchange mechanism, producing a salt as a by product. Figure 2. is a diagram which illustrates this reaction. Here, MMLHC in the chloride form reacts with sodium bentonite to produce the bentonite-MMLHC complex.
Figures 3 through 6 are transmission electron micrographs of specimens prepared by McAtee's techniques . Dilute dispersions were atomized onto grids chilled to -195C. The ice was then sublimed at 10- mm of mercury and the grids were sputter coated with carbon film to preserve the samples. The micrographs were taken with a JEOL 2000CX Analytical Scanning Transmission Electron Microscope.
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