Prevention of hematite settling using perlite in water-based drilling fluid

Abstract

The stability of the weighting materials in the high-density water-based drilling fluid was remarked as a serious issue to be controlled. It can cause several problems including formation fracturing, circulation loss, well control issues, etc. The usage of an anti-sagging chemical as a drilling additive is one of the sagging mitigation methods. In this study, amorphous volcanic alumina silicate (perlite) was evaluated as an anti-sag additive for hematite water-based drilling fluid. Several experiments were conducted to assess the perlite efficiency including static and dynamic sag test, mud properties measurements such as filtration behavior, filter cake properties, rheological and viscoelastic behavior. The tests were conducted at elevated temperature (250 °F). Perlite concentration was varied from 0, 1, 2, 3, and 4 lb/bbl. The obtained results showed that the loaded perlite was able to improve the mud stability and eliminate the sagging under static and dynamic issues at an optimum concentration of 4 lb/bbl. In term of filtration properties, there was an obvious improvement that could be observed through the reduction of filtration volume with 50% and filter cake thickness. In addition, the perlite contacting drilling fluid was able to form a thin and dense filter cake layer. The filter cake porosity and permeability were decreased by 24% and 68%, respectively. The rheological and viscoelastic behaviors were improved as well by the addition of perlite.