Investigation on Geothermal Drilling Muds with High Temperature Stability

Abstract

The aim of this laboratory research is to investigate different clays and other minerals as mud making base colloids and as additives to formulate mud compositions resistant to high temperature and brine environment for use in geothermal wells. The investigated mud compositions may also have potential for use in deep oil and gas wells.

The loughlinite and nontronite, rare clay minerals are found around Eskisehir and Canakkale regions of Turkey respectively. In this study, these minerals were investigated as drilling mud colloids and additives to the muds made up by sepiolite. In addition to loughlinite and nontronite, minerals such as borax and talc were also investigated as additives to sepiolite mud within the framework of this study. Various possible combinations of mud slurries were made up by using the above mentioned clays and minerals and then, their rheological and filtration properties were investigated to define a drilling mud composition with high temperature stability characteristics.

After discovering good filtration properties of loughlinite clay, it was considered to use it as an additive to sepiolite based mud, which itself has bad filtration characteristics, to reduce free water retention usually associated with sepiolite muds. As a result, water loss of sepiolite-loughlinite mud was reduced to acceptable levels. Moreover, loughlinite was also found to be resistant to chemical contamination and especially from the brines. When it is treated with saturated salt water, loughlinite provided good filtration properties. Finally, proposed mud slurry mixtures were aged under high temperature conditions, and the results are reported.