Thermal effects on differential pressure pipe sticking tendency

• Sticking coefficient of mud samples was strongly affected by temperature.
• Bentonite/polymer and lignosulfonate muds were thermally stable up to 121 °C.
• Undesirable edge effect was observed in bentonite/polymer and lignosulfonate muds.
• Stability of sepiolite muds extended up to 204 °C without edge effect.
• Sticking coefficient of sepiolite muds was stabilized with increasing set time.

Differential pressure pipe sticking as one of the common borehole instability mechanisms occurs when the overbalance pressure pushing drill string toward filter cake. The aim of this study is to experimentally investigate possibility of "stuck pipe" tendency taking place during the utilization of two commonly in use drilling fluids (Bentonite/Polymer, and Lignosulfonate based drilling fluids) and a new developed drilling fluid system (Sepiolite based drilling fluid) at elevated temperatures. Drilling fluid samples were thermally aged for 16 h up to 204 °C (400 °F). Rheological and filtration properties of samples were then measured for initial confirmation. After that, the samples were subjected to the differential sticking test under differential pressure of 3.447 MPa (500 psi). Sticking coefficients and corresponding sticking times were measured at various set times. Results indicated that Bentonite/Polymer and Lignosulfonate drilling fluids have lower sticking coefficients than those of sepiolite drilling fluids at temperatures below 121 °C (250 °F). However, the sepiolite drilling fluids demonstrated remarkable low sticking coefficients particularly above 149 °C (300 °F) implying low stuck pipe possibility due to the differential pressure. This study could contribute on providing database regarding the differential pressure pipe sticking tendency of various drilling fluids at elevated temperature.