Transport properties of offshore discharged synthetic based drilling cuttings

The general purpose of the present study was to study the transport properties of offshore discharged drilling cuttings produced with synthetic based drilling fluids (SBFs). The transport mechanisms include flocculation and settling. For this reason, a digital imaging system was developed to observe the time variation of floc size distribution under a variety of combinations of fluid shear, solid concentration, and salinity. The system was also employed to measure the settling velocities of both aggregated flocs and individual drilling cuttings particles of different shapes. The samples used in this study were collected from a production oil well on the east coast of Canada. Thermal treated samples were also used to study the effects of oleophyllic components on the transport properties. From the experiments, it was shown that the untreated cuttings flocculate faster and have much larger steady state median floc diameter than thermal treated cuttings due to the bridge effect of oleophyllic components. For the same cuttings, the steady state median floc diameter and time needed to reach steady state decreased as the fluid shear, solid concentration, and salinity increased. The settling velocity of flocs was found to be a function of both floc diameter and fluid shear. The settling velocity increased as the fluid shear increased. The solid concentration had no distinguishable effects on the settling of flocs in this study. The flocs produced from thermal treated cuttings settled faster than those produced from untreated cuttings. For individual particles with diameters larger than 0.1 mm, the equations of settling velocity were derived for both untreated and thermal treated cuttings particles. It was demonstrated by the experiments that the particle shape significantly affects the settling velocity of thermal treated cuttings particles of this size range, while it has no effects on the untreated cuttings particles. For cuttings with the same density, treated cuttings settles faster than untreated cuttings. Experimental results are presented and discussed in the paper.