The Development of a Geopolymer-Based Pill as an Engineered Solution to Lost Circulation

Lost circulation is a common and highly varied drilling challenge. Whole fluid loss can be the result of entry into a highly permeable zone, vugular formation, or natural or induced fracture. Losses are further impacted by variables such as engineering practices, wellbore conditions, type of fluid (drilling, completion, cement, etc.) and formation properties. A variety of materials and techniques have been developed to stop lost circulation and stabilize the wellbore. One of the more common fluid solutions is the use of a dedicated pill formulation. These technologies may be comprised of particulate and/or fibrous material that is completely inert, or may be a chemically reactive solution that is triggered to form a sealant throughout the thief zone. Historically, these pills have proven highly effective, but most function under a narrow set of conditions. Another technical limitation for the materials used as a pill treatment is lack of structural integrity (strength) and a reduced tolerance to higher temperatures. This paper presents a comprehensive summary of the development of a new type of chemically reactive pill based on aqueous alkali alumino silicate as the key component. The aqueous alumino silicate is a low molecular weight, low viscosity solution that is sometimes referred to as a “geopolymer”. Set times can range from several minutes to several hours based on the type and concentration of setting agent. By controlling the type, size and quantity of particulate material in the chemically reactive pill formulation, properties such as density, temperature resistance, strength and flexibility can be regulated to suit a wide range of lost circulation challenges. Models were developed on factors affecting set times, as well as properties of the uncured and cured formulas. These results are utilized to design a lost circulation pill that could be easily pumped through a bottomhole assembly over a wide range of loss rates and downhole conditions. The alumino silicate pill can provide strength properties approaching those of cement with a corresponding tolerance of high downhole temperatures. The environmental characteristics of the system and the economics of its application are also presented.