In Situ Combustion of Heavy Oil Within Carbonate Naturally Fractured Vuggy Reservoir
Creators: name: Fazlyeva, Rita
Publisher: name: Graduate Studies
Year: 2023
Subjects: subject: In situ combustion
subject: Air injection
subject: Carbonate reservoir
subject: EOR
subject: Accelerated Rate Calorimeter
subject: Combustion Tube
subject: Heavy oil
subject: Education--Technology
subject: Geology
subject: FOS: Earth and related environmental sciences
subject: Engineering--Chemical
subject: Engineering--Petroleum

description: Worldwide proven recoverable heavy oil and bitumen reserves make up more than 64 %, and more than 60 % of the world’s total oil reserves are trapped in carbonates. Air injection has immense potential for hydrocarbon recovery from various reservoirs. While most of the successful air-based techniques were performed within the carbonate reservoirs containing light oil, theoretically, in situ combustion (ISC) has great potential to recover heavy oil and bitumen from such reservoirs as well. However, carbonates are complex in geology and often associated with fractures and vugs, that affect the fluid flow, pressure propagation and progression of the ISC reactions. This research provides a comprehensive overview of the heavy oil properties and thermal behavior in response to air injection through various experiments using samples collected from a reservoir located in the European part of Russia; Accelerated Rate Calorimetry (ARC), Calvet C600 calorimeter and combustion tube (CT). Once the screening of the oil to ignite and maintain energy generation in the bond scission mode using ARC was confirmed, the study directed towards investigating the contribution of each fraction in the maltenes (saturates, aromatics, resins) as well as the asphaltenes with regard to heavy oil energy generation. After cross-verifying the obtained results from both calorimetry systems, the studies were shifted to a greater scale. The first feasibility experiment was performed using a CT in which the triple porosity concept was applied to resemble heterogeneity through artificially induced vugs, core matrix and fractures. The outcomes of this study provide a methodology to estimate the apparent heat of the reactions, identify a transition from the low-temperature to high-temperature oxidation mode and evaluate the thermal behavior of the whole oil and its SARA fractions using calorimetry results. The CT feasibility study results demonstrated a possibility to recover oil trapped in the separated vugs using air injection. The novelty of this work and the experimental approach followed in this study lies in the representation of the carbonate reservoir using core plugs physically fabricated and assembled to best resemble the actual reservoir conditions in terms of the complexity of the oil-bearing-formation-containing matrix, fractures and vugs. Post-ISC core assessment that involved XRD, CT-scanning, permeameter and visual analyses confirmed a significant decomposition of the dolomite core that was observed during the experiment, allowed to identify newly formed minerals as well as displayed alteration of the porosity and permeability parameters in the consolidated samples. The results of this experimental study can be incorporated into numerical reservoir simulators to improve the prediction capabilities and increase confidence prior to large scale field applications.