Investigation on the micro-structure and mesoscale transport behavior in the steel cord-rubber composites with lattice Boltzmann methodology

Abstract

Annular blowout preventer (BOP) is the vital equipment for sate well control. The internal porous microstructures and multiscale flow properties in the steel cord-rubber composites (SRCs) of annular BOP are directly related to the erosion area of drilling mud and rubber environment. However, current studies have rarely reported the fluid transport behavior in SRCs from a mesoscale viewpoint. The computed tomography (CT) scanning technology and lattice Boltzmann method (LBM) were innovatively introduced in this study to reconstruct and compare the real three-dimensional (3D) pore structures and fluid flow in the original and tensile SRCs. The results demonstrated that before and after the stretching, fluid velocities increased as displacement differential pressures increased in the SRCs, but with two different critical values of 3.6131 Pa and 3.1437 Pa, respectively; three transport channels can be observed, where the average and maximal velocities of primary flow channel were both greater than those of secondary flow channels; the average and maximal velocities in the primary flow channel of tensile sample increased by 222.8% and 241.03% than those of original sample. These phenomena should be attributed that when the original sample was stretching, its porosity increased, its micro-pore radius increased, and then its mesoscopic flow channel became wider, resulting in a lower critical value of displacement differential pressure, higher average and maximal velocities. However, the average seepage velocity at the 1/2 section in the original sample was greater than that in the tensile sample owing to the deteriorated connectivity of flow channel. Depending on the Zou-He Boundary and Regularized Boundary, the relative error of simulated average velocities was only 1.389%. The Xu-Yu fractal model always overestimated the permeability values, however, K-C equation underestimated the results.