Influence of ionic hydration inhibitors on triple inhibition system mud properties - clay rock swelling

A major problem during drilling clay rock is its swelling under influence of the mud filtrate. In relation to this, for clay rock drilling it is applied mud with inhibition system. Based on the analysis of industrial data (amongst others mud reports), it can be concluded that recently past years, while drilling clay rock, mainly mud with triple inhibition system is applied. In the light of abovementioned fact, it can be seen growing importance of studies related to improvement and development of this type of mud formulas. In the mud with triple inhibition system, three types of hydration inhibitors are used. The most common ones are: – polymeric inhibitors – out of those the most popular is PHPA-type polymer (partially hydrolyzed polyacrylamide), which contains about 30 of anionic groups (–COOH), – polyglycols – e.g. block oligomers of propylene oxide and of ethylene oxide with molecular masses of 1000–2000 atomic mass unit and with different turbidity temperature, – ionic inhibitors – mainly K+ ions originating from potassium chloride.