Investigating the Uniformity of In-Situ Asphaltene Deposits in Sandstone Rocks

The stability of asphaltene molecules is tied to the changes induced by temperature, pressure or composition. Therefore, the precipitation of these molecules is expected during various operations and at different stages of well life. While the deposition and remediation of asphaltenes in wellbores and pipelines are well-addressed, the deposition phenomena in reservoir rock and its impact on rock characteristics and fluid dynamics is still not well-developed. We have developed an experimental workflow to create a uniform deposit of asphaltene inside the core sample. The results show that injecting oil or a heptane/oil mixture results in a non-uniform deposition of Asphaltene, which was quantified using the TOC and density measurements. Uniform exposure to crude oil and deposition was obtained through vacuum saturation of the cores. However, permeability impairment is evident in both cases; whether the deposition is developed using vacuum-saturation or injection. Interestingly, the absolute permeability damage could be mitigated by reversing the injection flow direction which suggest that pore throat plugging is the main damage mechanism, while deposition onto the rock surface is the secondary damage mechanism for absolute permeability.