Improving the rheological properties of water-based calcium bentonite drilling fluids using water-soluble polymers in high temperature applications

Most of bentonite used in modern drilling engineering is physically and chemically modified calcium bentonite. However, with the increase of drilling depth, the bottom hole temperature may reach 180 °C, thus a large amount of calcium bentonite used in the drilling fluid will be unstable. This paper covers three kinds of calcium bentonite with poor rheological properties at high temperature, such as apparent viscosity is greater than 45 mPa·s or less than 10 mPa·s, API filtration loss is greater than 25 mL/30 min, which are diluted type, shear thickening type and low-shear type, these defects will make the rheological properties of drilling fluid worse. The difference is attributed to bentonite mineral composition, such as montmorillonite with good hydration expansion performance. By adding three kinds of heat-resistant water-soluble copolymers Na-HPAN (hydrolyzed polyacrylonitrile sodium), PAS (polycarboxylate salt) and SMP (sulfomethyl phenolic resin), the rheological properties of calcium bentonite drilling fluids can be significantly improved. For example, the addition of 0.1 wt% Na-HPAN and 0.1 wt% PAS increased the apparent viscosity of the XZJ calcium bentonite suspension from 4.5 to 19.5 mPa·s at 180 °C, and the filtration loss also decreased from 20.2 to 17.8 mL.

Lethal Dose of Calcium Bentonite in Wistar Rats

Background: Calcium bentonite is a type of clay produced by a devitrification of volcanic ash which is often used as a traditional medicine to absorb toxins and waste products of metabolism. The aim of this study was to determine the lethal dose of calcium bentonite in Wistar rats to explore its toxicity level and safe use.Methods: Fifty male and female Wistar rats were randomly divided into five groups for each sex. The control group was given 5 cc aquadest whereas the other four groups received calcium bentonite solution of 50 mg/kgBW, 300 mg/kgBW, 2,000 mg/kgBW, and 5,000 mg/kgBW, respectively, at a single dose. The weight was observed for up to 7 days and analyzed using the unpaired t-test and Mann-Whitney test. The death rate was calculated using the probit analysis. Median lethal dose results were then classified according to Loomis Criteria. Results: No deaths occurred at the highest dose, suggesting that the median lethal dose value of calcium bentonite was >5,000 mg/kgBW. No weight loss occurred due to the administration of calcium bentonite and a significant increase in the body weight was even observed in the male rat group. Interestingly, a significant decrease was found in the female rats group when compared to the control group.Conclusions: Calcium bentonite is classified as a practically non-toxic material with a median lethal dose of over 5,000 mg/kgBW.

INFLUENCE OF AN ORGANIC ADDITIVE ON THE STRUCTURE OF AN AQUEOUS SODIUM SILICATE FILM ON THE SURFACE OF A REFRACTORY CHROMITE FILLER

Formation of the structure of a film of hydrous sodium silicate on the surface of a refractory chromite filler. Wastes of contact cleaning of oils were used as organic additives, which are calcium bentonite impregnated with oils. The structure of liquid glass films on the surface of a refractory filler, cured at a temperature of 180-400-600-900 ° C, is investigated, which is comparable to the temperature convective system of liquid glass molds and rods, as well as the temperature system of molds after pouring with hot metal.