Experimental Study of Heavy Oil Recovery Mechanisms during Cyclic Solvent Injection Processes
Date
2019-03-22
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Abstract
In recent years, the Cyclic Solvent Injection (CSI) process has shown to be a promising method for enhanced heavy oil recovery in Canada. CSI laboratory studies work for only 2 to 3 cycles due to low incremental oil in subsequent cycles whereas field pilots continue for years over multiple cycles This experimental study is intended to capture the production mechanisms responsible for heavy oil production in CSI. Primary production and CSI tests were conducted using physical sandpack models saturated with live heavy oil of 9,530 mPa.s viscosity. The experiments were conducted in horizontal and vertical mode injection at high- and low-pressure depletion rates using two solvent mixtures of CH4 and C3H8. The sandpack was Computed Tomography scanned after every cycle to analyze the evolution of gas and oil saturations. Three cores were used to study the effect of gravity forces, depletion rate, solvent composition, and initial oil saturation (dead/live oil systems) on the performance of CSI processes. CSI after primary in horizontal systems produced negligible incremental oil for both slow and fast drawdown rates due to the large void space and high free gas saturation inhibiting the pressure build up to push the solvent-diluted oil. These CSI experiments were only successful in dead oil systems, where the initial oil saturation was high and pressure gradient was generated through fast depletion rates until conditions of high void space and gas channels were reached. When the sandpack was flipped vertically, CSI cycles exhibited higher incremental oil recovery per cycle. Slow depletion cycles were more efficient in terms of pressure and incremental recovery per cycle, however, faster depletion cycles performed better as a function of time. The higher C3H8 content solvent mixture exhibited better performance in comparison to the lower C3H8 content as higher volume of diluted oil was drained out of the core. These results demonstrate the importance of gravity drainage in the CSI process and its significance on successful oil recovery rates. This study illustrates the limitations of previous horizontal laboratory tests and shows an improved test configuration for modelling and prediction of the improved response observed in CSI pilots
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Keywords
Cyclic Solvent Injection, Solvent mixture, Depletion rate, Heavy oil recovery, Initial oil saturation, Gravity drainage
Citation
Plata Sanchez, M. A. (2019). Experimental Study of Heavy Oil Recovery Mechanisms during Cyclic Solvent Injection Processes (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.