Innovative Chemistry for Drilling Fluid Additives

Abstract

Abstract The enhanced performance of drilling fluids, especially High-Temperature, High-Pressure (HTHP) compatibility, will allow faster and safer drilling in challenging environments. This paper presents a novel class of synthetic polymers that were developed as high performance rheology modifiers (viscosifiers). The leading polymer candidate was shown to be an effective thickener, with excellent salt-tolerance and thermal stability compared to conventional viscosifiers used in water-based drilling fluids. This new class of synthetic polymers was suitable for demanding drilling conditions where conventional viscosifiers cannot perform satisfactorily. For example, xanthan gum is known to start losing rheological properties above 250-300°F so it is not always suitable for HTHP drilling operations. A desired rheology modifier should possess similar rheological properties to xanthan gum (e.g. highly shear thinning) with enhanced salt tolerance and thermal stability. These enhanced properties will allow drilling fluids to maintain critical functions under harsher field conditions. This paper presents the basic characteristics of the newly developed polymeric rheology modifier as well as its rheological and thermal stability properties. The rheological properties of the polymers were studied in fresh water, in brines and in formulated drilling fluids. Thermal stability studies were conducted using stainless steel pressure aging cells, a roller oven, and a conventional oven. The novel polymer developed was shown to exhibit a similar thickening efficiency and rheological profile (i.e. shear thinning) to xanthan gum. After thermal aging up to 350–375°F (177–190°C) for 16 hours, drilling fluids based on this polymer were shown to maintain excellent rheology and suspension power. The new synthetic rheology modifier also demonstrated synergistic effects with other ingredients commonly used in water-based drilling fluids, further enhancing thermal stability. Development of these high-performance drilling fluid additives is critically important to the drilling industry. HTHP compatible drilling fluids may allow more environmentally-friendly drilling operations to be undertaken in a safe and efficient manner.