Asphaltene inhibitors

Asphaltene deposition is complex, and varies from field to field, and even within the same field. Modelling of Asphaltene is difficult, though computer simulations of Asphaltene precipitation tendencies are possible. The most effective procedure is configuring the production conditions to reduce precipitation tendencies previously established for the well. This involves minimizing pressure drops within the production system—possibly fracturing the formation to minimize drawdown. The use of pressure maintenance by water injection might be appropriate if the field is of sufficient size.

If prevention cannot be achieved in this manner, chemical inhibitors can be used to prevent Asphaltene precipitation. The inhibitors must be placed in the oil before Asphaltene precipitation has taken place. In completion systems where capillary tubing already exists, a continuous injection of an inhibitor can be used. Continuous injection of an inhibitor into pipelined crude is straightforward, as well as the injection of inhibitors immediately before the mixing of Asphaltene in incompatible oils. Asphaltene inhibitors can be squeezed into the formation, similar to inorganic-scale inhibitors. However, these inhibitors are not necessarily oil soluble, resulting in a short functional lifetime for the inhibitor.

Asphaltene inhibitors are, generally, resinous organic polymers. Their functional groups interact with the Asphaltenes in much the same way natural resins keep the Asphaltenes dissolved. It is claimed that the strength of the interaction is stronger than with natural resins, keeping the Asphaltene dissolved over a broader range of pressures and temperatures. Given the variability in the Asphaltene structure, it is important that the polymer inhibitor be evaluated on the specific crude in which it will be placed. In principle, it is possible that these polymers could also cause formation damage by altering the wetting properties of the rock. It is obviously prudent to evaluate this possibility on core samples before treatment.