Esters were found to be promising alternatives to oil, as a constituent of drilling fluids, due to their biodegradability and bioaccumulation attributes. In this study, we used ethyl octanoate ester (EO) as a low molecular weight synthetic oil for formulating an ester-based drilling fluid (EBDF). Aluminum oxide nanorods (nanoparticles) were introduced as a Pickering emulsion stabilizer. Like the commercial emulsifiers, they showed that they stabilized the invert emulsion drilling fluid in our study. The rheological and filtration properties of the EBDF were tested at normal pressure and three temperatures: low temperature deepwater (LT) conditions of 2.6 °C, normal pressure and normal temperature (NPNT) conditions of 26.8 °C, and elevated temperature conditions of 70 °C. To enhance the stability and filtration properties of the drilling fluid, aluminum oxide nanoparticles (NPs) were used. An optimum concentration of 1 wt% was found to provide superior rheological performance and higher stability than samples without NPs at NPNT, LT, and elevated temperature conditions. Steadier gel rheology was exhibited at elevated temperature conditions, and a slow rate of an increasing trend occurred at the lower temperatures, with increasing NP concentrations up to 1.5 wt%. Filtration loss tests presented a reduction of fluid loss with increasing the NP concentration. The results demonstrate that a reduction of up to 45% was achieved with the addition of 1 wt% NP. These results show that nano-enhancement of ethyl octanoate drilling fluids would suffice to provide a wider range of operational temperatures for deepwater drilling operations by providing better thermal stability at elevated temperatures and maintaining stability at lower temperatures.

A new compound of probable formtda Ba3Ai2(OH)12 was formed at about 90°C from solutions of high BaO/AI203 ratio. Its composition could not be verified analytically because of contamination with hydrous alumina. Its unit cell (cubic, a= 13.16 ,~) and space group (Ia3d) are analogous to those of hydrogarnet [CaaAIE(OH)12]. Infrared studies and full structural analysis confirm that it is a barium analog~le of hydrogarnet.

The compound of approximate formula Ba0.A1203.H20 has been synthesised. Infra-red and X-ray studies suggest a structure based on a framework of AIO, tetrahedra. Thermal dehydration and differential thermal analysis curves are presented, and are explained in terms of the suggested structure.

The stability relationships of xonotlite, foshagite and hillebrandite relative to kilchoanite and calcio‐chondrodite have been studied under saturated steam pressures at 180° and 250°. Kilchoanite was unstable relative to xonotlite plus hillebrandite at 180°, or to foshagite plus hillebrandite at 250°; calcio‐chondrodite was unstable relative to hillebrandite plus some more lime‐rich phase, possibly Ca(OH)2, at both temperatures. Foshagite was stable relative to xonotlite plus hillebrandite at 250°, but unstable relative to these phases at 180°.

A new compound of formula 2BaO·Al2O3·2H2O has been synthesised and studied by infra‐red, X‐ray and thermal analytical techniques. This hydrate yielded another crystalline product, 2BaO·Al2O3, during dehydration.