A novel packer fluid for completing HP/HT oil and gas wells

Abstract

Today, many oil and gas resources in onshore and offshore environments worldwide are often in high-temperature, high-pressure and low-permeability reservoirs, creating challenges for well completion in these reservoirs. Thus, designing a completion fluid which is solid-free and has high-density and high-thermal resistance is essential in the oil industry. Parameters that make it more challenging to choose a completion fluid include: cost-effectiveness, availability of components, low corrosion rate, environmental compatibility, fluid stability, compatibility with the reservoir, low crystallization point, high density, suitable pH, and low damage potential. The primary purpose of this study is to overcome these parameters. In this study, a novel packer fluid for well completion was developed using potassium hydroxide and phosphoric acid for the first time. The novel packer fluid is a brine that can act as a high-density, solid-free fluid during drilling and completion in HT/HP reservoirs. This brine is prepared using an experimental design in three different densities and is compared with potassium formate and calcium bromide. Potassium formate is prepared from the reaction of potassium hydroxide and formic acid, while potassium hydroxide is cheaper and more available compared to other brines. The results show that novel brine is stable at changes in density and pH under surface and bottom-hole conditions. The concentration of toxic elements in the novel brine indicates that this brine is environmentally compatible. The corrosion rate of L80 steel after contact with novel brine at temperatures above 180 and 300℉ is low and very close to traditional completion fluid. In addition, return permeability of the carbonate core can reach 88.38% of the initial permeability. The novel brine is compatible with formation water, and has excellent performance against clay swelling. Furthermore, results of the wettability test show that novel brine causes changes in the wettability of carbonate core from oil-wet to water-wet conditions.