New Insights from an Old Method after History Matching a Newly Designed 1D Cyclic Steam Stimulation Experiment

Summary A cyclic steam stimulation (CSS) laboratory experiment was conducted with dead heavy oil. Four cycles of steam injection and fluid production were performed, at reservoir pressure, to assist in the numerical modeling and understanding of the main mechanisms involved in the process. This was an important step in developing a base model for a broader project evaluating CSS steam-hybrid experiments with live oil. Experimental data, history matching approach and results, as well as key insights are presented. An experimental setup, originally designed to evaluate CSS hybrid processes, was improved by fitting a sight glass to identify the fluids flowing out of the opposite core end (into a ballast system), during injection cycles. Dead oil was used to facilitate the analysis of this experiment. Relative permeability curves were tuned to history match each cycle sequentially. Injection periods were matched before production ones to estimate the amounts of oil and water displaced to the ballast during injection (unknown, although total liquid volumes in the ballast were recorded continuously), which were later injected back into the core during production periods. A 1D grid represented the core section, while the ballast system was modeled with a production well and an injection well. Experimental data such as temperature profiles, pressures, and rates were honored. A volumetric ratio of 40% water and 60% oil appeared to be the typical composition of the fluid received by the ballast during injection periods, based on simulation results. Fluids reinjected from the ballast back into the core were modeled as an emulsion (i.e., a water-oil mixture). Relative permeability curves were the same for injection and production periods within the same cycle, except for an increased critical water saturation during the last two production periods. One set of relative permeability curves was obtained for each of the four cycles. Although all the cycles of the CSS experiment were history matched successfully using water-oil relative permeability curves, the need to have different curves for each continuous cycle suggests that different flow phenomena were taking place during the CSS test. After reviewing different mechanisms associated with steam injection processes, it appears plausible that injected steam, after condensing to water, partially emulsified with the heavy oil in the core. Insights from this work suggest a need to rethink the traditional way of modeling heavy oil recovery with steam, where water-in-oil emulsion formation typically occurs.

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