Comparison of Experimental Techniques for Evaluation of Chemistries against Asphaltene Aggregation and Deposition: New Application of High-Pressure and High-Temperature Quartz Crystal Microbalance

Asphaltene precipitation and deposition caused by temperature variation, pressure depletion and oil composition changes can result in formation damage, oil production reduction and increased operating costs. Use of chemical additives is probably the most effective option for preventing or reducing asphaltene problems. Selection of inhibitors for asphaltene deposition is commonly based upon simple tests conducted on stabilised crude oil samples at ambient conditions. The results obtained from the current testing techniques in the labs are sometimes in disagreement with the outcome at field conditions. Therefore, the current techniques which are employed to select the most appropriate asphaltene inhibitor based on their efficiency should be revisited to provide a better methodology for choosing the most suitable strategy for inhibitor/solvent injection.
This research study addresses this asphaltene challenge using a Quartz Crystal Microbalance (QCM) based technique, with emphasis on selection of chemical additives for remediation/prevention strategies to handle gas induced asphaltene deposition problems. The proposed technique can work at high pressure conditions, simulating the effect of pressure and dissolved gas on asphaltene phase behaviour and deposition tendencies with and without inhibitors. It can also assess the deposition rate onto the quartz crystal surface due to asphaltene deposition under real reservoir conditions. In this study, the ability of different asphaltene inhibitors to shift asphaltene onset points (AOPs) and reduce the amount of deposited asphaltenes in dead crude oils is investigated. A comparison between the results of the QCM technique at high pressure-high temperature and dead crude oil testing at ambient condition is presented. The results of this work indicate that the change in temperature, pressure and presence of gas could alter the ranking of chemistries for mitigating asphaltene challenges.