Analysis of formation damage and fracture choking in hydraulically induced fractured reservoirs due to asphaltene deposi
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ORIGINAL PAPER--PRODUCTION ENGINEERING
Analysis of formation damage and fracture choking in hydraulically induced fractured reservoirs due to asphaltene deposition Ilyas Khurshid1 · Emad Walid AlShalabi1 · Hazim Al‑Attar2 · Ahmed Khalifa AL‑Neaimi3 Received: 17 March 2020 / Accepted: 11 May 2020 © The Author(s) 2020
Abstract 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. In this work, a 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. Primarily, a numerical model is developed to predict the rate of asphaltene deposition and fracture choking in a radial geometry. It is found that asphaltene deposition could partially or completely choke fractures. Finally, the results are compared with the experimental data and determined various factors affecting fracture choking. From the detailed analysis, it is found that fracture choking is a few percent, but it increases with long production time. The sensitivity analysis was performed to investigate the effect of different influential parameters on permeability alteration of fractured reservoirs by asphaltene deposition. These parameters include fracture-to-matrix permeability ratio, production time, and asphaltene concentration. It is observed that, low fracture-to-matrix permeability ratio has a negligible effect on permeability of a reservoir. The developed model assumes negligible gravity and capillary forces. However, these forces might increase fracture choking in unconventional fractured reservoirs. Keywords Oil production · Pressure drop · Precipitation · Flocculation · Asphaltene deposition · Formation damage · Fracture choking List of symbols A Reservoir area (m2) B Formation volume factor (res-bbl/STB) d Asphaltene deposition rate E Activation energy (J/mol) f Fracture width (m) G Deposition rate of asphaltene h Height (m) k Reservoir permeability (m2) K Reaction rate coefficient n Conversion factor * Ilyas Khurshid [email protected] 1
Khalifa University of Science and Technology, Abu‑Dhabi, UAE
2
Chemical and Petroleum Engineering Department, UAE University, Al‑Ain, UAE
3
Reservoir Engineering Department (Zakum), Abu-Dhabi National Oil Company (ADNOC), Abu‑Dhabi, UAE
P Reservoir pressure (psi) q Flow rate (STB/day) Q Fluid flow rate (m3 per unit time) R Gas constant (J/mol K) s Skin factor S Saturation (%) t Time (h) T Reservoir temperature (K) v Fluid flow rate (kg/h) V Volume (m3) w Width of fracture (m) x Fracture half-length (m) X Concentration Z Rate of asphaltene deposition on fracture face Greek le
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