Electromagnetic devices (EMDs) have been reported to be a method for scale management in the field. One proposed mechanism for scale mitigation is that the device imparts an electromagnetic (EM) pulse that provides sufficient energy to the fluids to cause homogeneous nucleation, resulting in the formation of very small particles (5 to 9 µm), which will pass through the production system, hence preventing/reducing heterogeneous nucleation and deposition on the tubing surface. Previous work revealed that such a device had a measurable impact on a Barium Sulphate scaling system. This paper extends this work by performing visualisation experiments and comparing the results with baseline findings previously published in 2016 using the same test apparatus.
Comparative experiments were performed with the device "on" and "off" and images of crystal growth within the test cell taken at regular intervals over the test period. The same conditions as those from 2016 (scaling brines (SR), T, P and Q) were used and then extended by increasing the residence time of the fluid in the test cell by a factor of 2 and 4. The images were analysed using MATLAB to quantify the number of crystals formed, their size and the surface coverage achieved. ESEM images of the test coupon within the cell were also taken for analysis.
From all the comparative experiments performed, it was seen that the EMD had a significant, measurable, and positive effect on BaSO4 control with a reduction in crystal growth rate, crystal size and the numbers formed. Comparison with previous data were consistent with results obtained with a lower SR scaling system, suggesting that the EM signal has effectively reduced the surface saturation ratio of the system as it passes through the test cell. Increasing the residence time of the fluid within the EM field enhances the impact of the device in terms of the number of crystals formed, their size and surface coverage within the cell. All these observations support the previously proposed mechanism, that the EMD promotes bulk (homogeneous) nucleation and precipitation, and therefore reduces the energetic favourability of surface (heterogenous) crystal formation.