Drag reduction characteristics of RJD-suitable surfactant-polymer composite fluids under high shear.

Radial Jet Drilling (RJD) provides favorable conditions for exploitation of coalbed methane (CBM). However, the jetting medium always remains in a high-shear state (Re >> 1 × 105) during the construction of RJD, with significant pressure loss that is difficult to control. In this paper, two surfactant-polymer composite systems for high-shear conditions are firstly preferred: CTAC-PEO and OTAC-PEO, with drag reduction rates (DR) of 31.92 % and 21.97 %, respectively. Secondly, three fluids were further optimized by adjusting the ratio and concentration of drag reducers: CP11–1000, OP41–1000, and OP41–3000. Their drag reduction characteristics were investigated at different temperatures and shear durations. Among them, the average DR of OP41–3000 at 55 °C is 2.28 and 2.95 times that of CP11–1000 and OP41–1000, respectively. Moreover, terminated DR after 30 mins of cyclic shear is 4.74 and 7.5 times greater than that of them, with a drag reduction retention rate exceeding 80 %. Finally, the "laminae encapsulate chains-network structure" was proposed to explain the mechanism of drag reduction under high shear. This study is the first to investigate drag reduction from the perspective of the jetting medium. The research findings will improve the future advancement of CBM mining utilizing RJD. Additionally, this study can assist in the selection of appropriate drag reducers for high-shear environment and the exploration of drag reduction mechanism. [ABSTRACT FROM AUTHOR]