The practice of scale squeeze treatments to oil and gas production wells to prevent inorganic scale formation has been used for over 30 years. The test methods used for selection of chemicals for these treatments are well understood. Performance testing to determine a minimum effective dose (MED) followed by core flood testing to understand propensity for formation damage has been conducted successfully for many years to allow chemical selection.
This paper describes the steps taken to qualify a new source for a common squeeze scale inhibitor chemistry. Samples from an established supplier were compared with those from the potential new supplier. Physical properties were compared and showed no difference, and the chemicals performed similarly in static jar tests for sulphate scale control. Further testing in a coreflood test confirmed that no formation damage resulted from application of either chemical. Return profiles from the chemical tests indicated similar squeeze lifetimes would be expected for both chemicals.
Further testing was conducted to confirm similar performance following desorption from the reservoir. Static jar tests were conducted using samples taken from the postflush of the coreflood. These indicated very different performance from the initial tests. The sample from the potential new supplier did not perform at the same MED, or at higher dose rates tested. This can be attributed to a difference in the weight distribution of the chemical, which results in different rates of desorption which impacts the sulphate scale inhibition performance.
The results shared in this paper will indicate the importance of ensuring tests conducted to qualify new sources consider more than simple physical properties but also the application environment of the chemical. Testing for continual injection application would have passed the alternative chemical as suitable. However, for squeeze applications, the variation in molecular weight reduced the chemical's sulphate scale inhibition, only observed in coreflood effluent performance tests.
This paper clearly shows that specific evaluation of chemicals under appropriate field conditions are critical to ensure appropriate chemicals are selected and applied in the field.