Browsing by Author "Haghighat, Parnian"

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    Effect of Temperature on Performance of Vapex Process for Heavy Oil
    (2014-01-30) Haghighat, Parnian; Maini, Brij; Abedi, Jalal
    Incorporating some heat injection along with the solvent injection appears to be the most viable option for improving the oil drainage rate of Vapex (Vapor Extraction) in extra-heavy oil formations. This study was aimed at quantifying the upper limit of oil rates achievable with heated solvent injection. Results of the performed research can also be used to assess the applicability of Vapex to naturally warm reservoirs and reservoirs with mobile oil in place. The experimental phase of current research involved conducting Vapex experiments in a high-pressure physical model, packed with 250 Darcy sand, saturated with Athabasca bitumen (Mackay River) using propane as the solvent. The physical model was pre-heated to 40, 50 and 60 °C and propane was injected within 0.817 to 1.55 MPa pressure to investigate the effect of temperature elevation and injection pressure on Vapex performance. Due to the mobility of the original oil in place at elevated temperatures, the total rate of oil production is controlled by two mechanisms: 1. solvent dissolution and oil mobilization at the boundaries of the vapor chamber 2. free fall gravity drainage of undiluted oil within the sand matrix beyond the solvent penetration zone. To evaluate warm Vapex performance under different operating conditions, the contribution of free fall gravity drainage to total recovery was experimentally and numerically determined. Experimental results were compared against Vapex analytical models and a reported empirical correlation. The empirical correlation was modified based on the findings of the current experimental study by incorporating the effect of live oil viscosity into the original correlation. The experimental results of warm Vapex tests were numerically simulated with a commercial compositional simulator, Computer Modelling Group’s (CMG) GEM. Bitumen characterization and thermo physical modeling of bitumen/propane system were performed as part of the numerical study. The developed simulation model verified by the experimental production data was used to extend the study to wider ranges of temperature. Results of the current study indicates that elevating the reservoir temperature to 50oC without increasing the injection pressure, can improve production rate only by 70% and reservoir temperature elevation to above 60 oC is required to achieve more impressive rate increase of nearly 200% when Vapex is performed in heavy oil reservoirs.
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    Impact of asphaltene precipitation on vapex performance
    (2008) Haghighat, Parnian; Maini, Brij B.
    The VAPEX (Vapor Extraction) is an oil recovery process, in which heavy oil or bitumen is mobilized by injection of a low molecular weight hydrocarbon solvent and is drained by gravity to a horizontal production well. It has attracted considerable attention because of its potential applicability to problematic reservoirs and the chance of in situ upgrading of the oil during the process. The objective of the current work was to determine whether the beneficial effects of asphaltene precipitation will outweigh any formation damage in Vapex operations. The effects of in situ precipitation and deposition of asphaltenes on the rate of oil drainage and the quality of the produced oil under different operating conditions were experimentally evaluated. The experiments were conducted in a physical model packed with realistic permeability sand and propane was used as the solvent. The experimental results show that the oil produced at higher injection pressures was substantially upgraded but the viscosity reduction by asphaltene precipitation did not lead to higher rates of production. The effect of viscosity reduction was negated by the accompanying damage to formation permeability. Injection of toluene with propane was successful in increasing the rate of production and the extent of upgrading was encouraging. The huff and puff injection of toluene into the production well, to remove damage from the near well zone, was not successful. It led to production of oil with higher asphaltene content and there was no improvement in the rate of oil drainage compared to lower pressure operation with minimal asphaltene precipitation.