Experimental Study of the Multiphase Flow of Sand, Viscous Oil and Gas in a Horizontal Pipe

Abstract This study provides horizontal pipe pressure drop and liquid holdup measurements for three-phase flow of sand, viscous oil and gas with a focus on slug flow. We developed a correlation for predicting the liquid holdup and dimensionless pressure gradient in the presence of solids during slug flow. A multiphase flow loop facility with 1.5in (0.0381m) Schedule 80 PVC pipes was designed and constructed to flow viscous oils ranging from 150 to 218cP (0.15 to 0.218Pa-s). A progressive cavity pump (PCP) was used to pump the complex mixture from a double walled steel tank. Compressed air was used as the gas phase and 0 to 1% of 180μm diameter sand by weight was added to the flow. The facility had a clear test section for flow pattern visualization and photography. Equipment issues and operational difficulties in the setup were identified during initial tests and rectified. Oil and gas flow rates, differential and absolute pressures, liquid holdup (both with and without the presence of solids), and fluid temperatures were measured and flow pattern observations were photographed. Gas and viscous oil superficial velocities ranged from 0.5 to 10m/s and from 0.1 to 1m/s respectively. We validated the setup by comparing actual single phase liquid pressure drop measurements to an analytical expression for computing the pressure drop during single phase viscous oil flow. Sand was introduced into the system thereafter. We found that the presence of sand did not shift the flow pattern boundaries appreciably and slug flow was the most commonly encountered flow pattern. As such, we focused on the slug flow region. Slow motion photo and videography revealed that the presence of sand disrupted the sharp head and tail profiles in the liquid slug body. Regression analysis using the observed data revealed that for slug flow of viscous oil and gas, the most important dimensionless groups affecting both the holdup and the dimensionless pressure gradient are the fluid velocity numbers and the Froude number. For three-phase slug flow of sand, viscous oil and gas, the most important dimensionless groups for affecting holdup in the presence of solids are the fluid velocity, Reynolds, and Froude numbers in addition to the pipe diameter number and the sand fraction in the flow stream. For dimensionless pressure gradient, the most important dimensionless groups are the fluid velocity numbers, the Reynolds/Froude numbers and the input liquid fraction. Slug unit length was also measured and the data was matched with an existing correlation. We also detailed the effect of sand on pattern behavior in each of the commonly observed horizontal pipe multiphase flow patterns using videography. To the best of our knowledge, this is the first recorded attempt at measuring pressure drop and liquid holdup in the presence of solids for the horizontal multiphase flow of sand, viscous oil and gas. This work provides laboratory data/models that can support the characterization of the pressure drop and flow patterns experienced in horizontal wells completed using the Cold Heavy Oil Production with Sand (CHOPS) process and other viscous oil producing wells.