Rapid, green synthesis of high performance viscosifiers via a photoiniferter approach for water-based drilling fluids

Abstract

The generation of high-performance materials under benign conditions is very much needed in the efforts to reduce the carbon footprint of oil and gas explorations. Developing high performance novel additives for drilling operations that help reduce material consumption, and inevitably carbon consumption, through improved tolerance to harsh and extreme environmental conditions is an area that has been gaining momentum. Viscosifiers play a crucial role in water-based drilling fluids as they help in suspending and transporting formation cuttings during drilling operations. Natural viscosifiers such as xanthan gum are cost effective options, but they do not perform well at temperatures above 100 °C due to thermal degradation. Linear synthetic polymers, such as partially hydrolyzed polyacrylamide (PHPA) and modified starches, provide higher thermal stability, but they are unable to resist shear degradation due to mechanical stress. Therefore, more effective viscosifiers that are able to provide thermal stability for high temperature, high pressure (HTHP) drilling while providing high mechanical stability during high shear rate and high flow velocity are very much needed. This study provides a green, sustainable approach for designing such novel viscosifiers. In this study, a photoiniferter approach was employed to synthesize ultra-high molecular weight (UHMW) linear block copolymers and UHMW branched block copolymer microgel viscosifiers in a short duration (∼1 hour) under aqueous conditions by using mild UV irradiation. These viscosifiers required no additional purification as monomers (∼99%) were completely consumed at the end of the reaction. The UHMW branched block copolymer microgels were found to be excellent viscosifiers for HTHP drilling as they provided superior viscosification, higher mechanical and thermal stability, and greater shale inhibition capabilities over commercial PHPA viscosifiers and linear UHMW block copolymers.