Bulk Scale Analysis - Case histories
There are many, many case histories where BSA is used for cost effective scale management decisions. A few are shown below.
A customer squeezed wells based on potential of calcium carbonate deposition. The preventive strategy was selected because any scale removal operations would be costly.
The strategy is now changed. Instead of preventive costly squeeze operations, BSA is used to verify if actual scaling takes place or not. It turns out that the scaling tendencies are less than estimated, and no wells have been squeezed since startup of BSA. Million of dollars are saved by use of BSA only for this case alone.
This example shows how BSA is used to optimize the timing to re-squeeze wells. Usually, re-squeeze is done when the back-produced inhibitor concentration (RSI) decline towards the Minimum Inhibitor Concentration (MIC). However, this strategy will always be uncertain because MIC is measured at lab conditions and since the scale inhibitor can be unevenly distributed along the wellbore. Many oil companies now use BSA to secure a better decision basis for the timing of re-squeeze. This secure that the re-squeezing not is too late and not unnecessarily early.
The graph below illustrates how squeeze lifetime can be extended by use of BSA, instead of re-squeezing when the Inhibitor concentration is in the range of MIC, the timing relyes in BSA result.
BSA can be successfully used to verify the placement of scale squeeze, one case is shown below. Despite squeezing and high inhibitor concentration in the back produced fluid, the sulphate coverage is very high on the filter. This indicate that part of the well is unprotected, despite the recent squeeze. In this case a new squeeze using higher pumping rate was successfully performed and the low sulphate coverage verifies the improved placement.
Graph showing sulphate coverage over time (bars) and inhibitor concentration (blue line). Despite squeeze and high inhibitor concentration, the BSA indicate severe scaling in the well. This is because of poor placement, and this is corrected by increase in pumping rate in the next squeeze.