Next Generation High Performance Invert Emulsion Drilling Fluids with Flat-Rheological Behavior

Abstract

The rheological properties of drilling fluids are crucial parameters for efficient drilling operations. Invert emulsion drilling fluids are the industry's preferred choice when it comes to extreme conditions like deepwater or high temperature and high pressure (HTHP) drilling due to their inherent thermal stability and effectiveness against water sensitive formations. In addition, another highly desired property of such drilling fluids is minimal sensitivity of the fluid flow properties for a wide range of application temperatures, known as flat-rheology behavior. We have developed four novel and next generation chemical additives: (i) a high temperature stable emulsifier, (ii) a low-end rheology modifier, (iii) a viscosifier with covalently linked organic groups, and (iv) a fluid loss control additive. Molecular architectural designs and synthesis of all four chemicals were carried out in our laboratory and used in optimum quantities to build industry's next generation invert emulsion fluids at density ranges from 75 – 135pcf (10-18ppg) and application temperature range of 60-450°F. Rheological and other important drilling fluid properties were tested at different downhole pressures and temperatures using a standard API recommended HTHP apparatus. The results demonstrated extreme thermal stability all the way from 60-450°F with excellent fluid loss control and ultrathin filter cake. The novel covalently-linked organophilic viscosifier used herein has proven superior thermal stability compared to existing organo-clay based systems especially at temperatures above 350°F. Novel secondary emulsifier and low-end rheology modifier have demonstrated excellent emulsion stability at temperatures up to 450°F. It has been an industry challenge to obtain true flat rheological behavior under high pressure and temperature using commercially available chemistries. However, very interestingly, fluids optimized in this work have exhibited excellent flat-rheological behavior for a wide range of temperatures. We will present a comparative analysis of the relationship between molecular structure and properties perspective of what is currently used in the industry versus those developed in this work. The current work has led to development of four novel chemical additives which are responsible for the industry's next generation high performance invert emulsion drilling fluids with flat-rheological behavior.