Formate Brines for Drilling and Completion: State of the Art

Abstract

Abstract Low solids drilling fluids based on formate brines (sodium, potassium and caesium salts of formic acid) were originally designed to minimise frictional pressure losses in slim hole drilling applications. In addition, their unique capability of stabilising polymers to high temperatures made them more temperature resistant than any other polymer based drilling fluids. Subsequent work has shown that these brines, because of their high densities and low corrosivity, are also ideal completion and packer fluids. Formate brines have excellent HSE profiles and they are compatible with reservoir fluids, good shale stabilisers, gas hydrate inhibitors, and scale dissolves. Also, a technique has been found for cost effective clean-up and recycling of formate based drilling fluids. The commercialisation and introduction of these fluids into the field (especially caesium formate) has taken a long time, due to high prices and few manufacturers. This situation is now changing, as the number of manufacturers is increasing, and buy-back arrangements have been made available. Also, a number of successful drilling and completion trials have been carried out.