Abstract Of Paper.docx

In the drilling process, shales account for 75% of the all footage drilled and are responsible for 90% of wellbore stability problems (Steiger and Leung, 1992). Uptake of water in shale weakens the wellbore and causes problems such as hole collapse and stuck pipe. Maintaining wellbore stability is one of the most critical aspects of drilling. Therefore, for many decades, a large research effort has been directed to address the shaleswelling inhibition problems. A variety of water-based drilling fluids and non-aqueous fluids have been used, meanwhile many kinds of shale stabilizing additives have been developed. Van Oort (2003) classified these clay stabilizers into several groups, including inorganic salts, formates, polymers with special shale affinity, asphalts, sugars and sugar derivatives, glycerols and glycols and silicates. These fluids have not been completely successful in inhibiting the hydration of highly water sensitive clays and have various limitations. Oil based drilling fluid provides a definite solution to avoid borehole instability when drilling through water-sensitive shales. Compared to water-based drilling fluid, oil-based drilling fluid has many inherent advantages, including excellent clay inhibition, wellbore stability, lubricity, anti-accretion property, temperature stability, tolerance to contamination, and corrosion protection (Dye et al., 2006). However, increasingly strict environmental regulations limit its wide range of application. Salts like potassium chloride can inhibit the swelling of clay, however it's highly flocculating and its presence in the mud can adversely affect rheology and filtration control (Chesser, 1987). Moreover, a large quantity is needed for its inhibition, which adversely affects the environments and results in high costs for disposal. Silicate sodium exhibits highly inhibitive properties but has problems relating to rheological control. Cationic polymers have been proved to be almost as inhibitive as oilbased drilling fluid. However, their incompatibility with other anionic additives limits application in the field. Therefore, developing a novel water based drilling fluid that will provide performance like oil-based drilling fluid and be environmentally acceptable is paramount to continue economically viable drilling operations. Most clay inhibitors act on the principle of replacing a cationic species in the clay crystal layer for a sodium ion, which motivates researchers to use amine compounds to substitute traditional prior art materials to acquire better effects (Gholizadeh-Doonechaly et al., 2009 ; Horton and Jones, 1998). Amine compounds and derivatives have been used as shale inhibitors for a long time. Patel et al. (2007) reviewed the development of amine (ammonium) derivatives as shale inhibitors, and classified the amines into three major categories. He summarized the chemistry, functionality and some of the shortcomings of various kinds of amines (Patel, 2009). However the first generation of amine compounds displayed poor result, and the evolution of the amine compounds lead to higher inhibition level. Therefore, a novel nitrogencentered derivative called polyether diamine was then introduced. Due to its excellent inhibition and low toxicity, the low-molecule-weight polyether diamine was chosen as shale inhibitor. Based on this shale hydration inhibitor, a new type of high performance water-based drilling mud (HPWBM) which also includes dispersion suppressant, rheological controller, filtration controller and accretion suppressant, ha