Hydraulically induced fractures provide a significant fraction of oil supply to the world from unconventional reservoirs due to their high permeability. However, these fractures might choke because of the deposition of organic and in-organic particles. Among organic particles, asphaltene deposition severely reduces reservoir permeability causing an exponential drop in production. The objective of this study is to derive a model that characterizes formation damage and hydraulic fractures choking in unconventional reservoirs due to asphaltene deposition on fracture face and pore surface. This study also analyzes different factors affecting permeability alteration by asphaltene deposition in fractured reservoirs.
In this work, a 1D simulator is developed that predicts the performance of fractured reservoirs by solving the fluid flow governing equations for matrix and fractures. These flow equations were then incorporated with asphaltene deposition equations. The developed model considers constant temperature of the reservoir with negligible gravity and capillary forces. Sensitivity analysis was also performed to investigate the effect of three influential parameters on permeability alteration of fractured reservoirs by asphaltene deposition. These parameters include fracture-to-matrix permeability ratio, production time, and asphaltene concentration.
The study showed that asphaltene deposition could partially or completely choke fractures. This finding is in match with observations in the literature for asphaltene deposition and the consequent fracture choking. The sensitivity analysis showed that long production time and high asphaltene concentration have adverse effect on fracture permeability while matrix permeability was not much affected. On the other hand, low fracture-to-matrix ratio has a negligible effect on permeability of the simulated reservoir model. This work provides an insight into the detrimental effect of asphaltene deposition and estimates fracture choking in hydraulically fractured unconventional reservoirs with problematic oils.