Flow properties of water-in-North Sea heavy crude oil emulsions

In the present research, rheological and pipeline flow properties of North Sea heavy crude oil emulsions (w/o) were investigated using a stress-controlled rheometer and lab scale flow rig. The rheological properties of the emulsions were studied at different aqueous phase volume fractions (ϕ) from 0.0 to 0.70, temperatures from 20 °C to 50 °C, and shear rates from 0.1 s−1 to 1000 s−1. The rheology measurements indicate the crude oil and emulsions exhibit strong shear thinning at low temperatures and the power law fits quite well the rheology data of the crude oil as well as emulsions. Viscosities of the emulsions were determined from the rheograms at different shear rates and temperatures and modeled successfully using the Pal and Rhodes viscosity equation. Droplet size distributions measured using the Nuclear Magnetic Resonance (NMR) and digital video microscopy (DVM) techniques indicate the emulsions have an average droplet size of around 3–4 μm. The pipeline flow properties of the emulsions were investigated in a 3 m horizontal test section of pipe with 0.0221 m inner diameter using the lab scale flow rig at different aqueous phase volume fractions from 0.0 to 0.50 and flow rates from 0.10 m/s to 0.70 m/s for 50 °C. The pipeline flow measurements indicate the pressure gradients (ΔP/L) in the pipeline increase as a function of aqueous phase volume fraction and flow rate and water and North Sea heavy crude oil flows are not fully dispersed at aqueous phase volume fractions above 0.10.

► Flow properties of North Sea heavy crude oil emulsions (w/o) were studied.
► Power law fits sufficiently for all emulsions.
► Pal and Rhodes model predicts viscosity of emulsions.
► Pressure gradients in pipe increase with increasing aqueous phase and flow rate.
► Free water layers exist in pipe when flow rate is between 0.10 m/s and 0.70 m/s.