CFD simulation of viscosity modifier effect on cutting transport by oil based drilling fluid in wellbore

• The effect of viscosity modifiers were simulated on cuttings transportation in wellbore.
• As the value of viscosifier increases, it becomes easier to clean out particles.
• As the viscosifier content of fluid augments, pressure drop increases constantly.
• Cuttings transport decreases as concentration and density of cuttings increases.

In this study particle transportation has been predicted in a wellbore for an oil based drilling fluid containing viscosity modifier using CFD simulation. The effects of fluid viscosity on particle transport capacity of fluid were studied by considering various particle parameters such as density, diameter, shape, and initial particle concentration and wellbore inclination through using the Algebraic Slip Mixture (ASM) model. Rheology of the drilling fluid was expressed by Herschel–Bulkley non-Newtonian fluid model. The influence of viscosifier concentration on fluid rheology show that it improves carrying capacity of particles but its effect attenuates in higher concentration. For 2 ppb of viscosifier in drilling fluid, the cutting transport capacity has been increased almost 12% whereas adding 4 ppb of viscosifier, only created about 14% escalation on the transportation of cuttings. Against this positive effect viscosity modifier make more pressure drop that was a costly effect for operation and this effect had constant rate (for each ppb viscosifier, pressure drop growth is equal to 200 kPa/m approximately). Also, the results indicate higher particle density or larger particle size results in less particles transportation in the wellbore. Increasing initial solid loading has an adverse impact on the transmission of solid particles in wellbore.