Master of Science in Petroleum Engineering (MSPE)
CO2 displacement is the most widely used EOR process, but poor sweep efficiency and large CO2 utilization rates are limitations to the economic and technical success of CO2 floods. Developing a methodology to maximize the sweep efficiency and minimize the CO2 utilization rate would greatly improve the economics of these fields. This thesis evaluates the sweep efficiency of a successful, late-in-life, continuous injection CO2 flood at the Little Creek Field, Mississippi. In this work, we evaluate several heterogeneity measures in terms of recovery efficiency and utilization rate. Core studies available from 41% of the wells in the field were used to compute various heterogeneity measures, and the resulting values were correlated with pattern-by-pattern recoveries and CO2 utilization rates. Weak correlation trends were found for most of the measures in terms of R2 values. However, there was still a trend confirming the idea that more heterogeneity corresponds to higher utilization rates and lower recoveries. Mapping of the well-by-well heterogeneity measures appear to show geological trends better than traditional maps of the basic parameters that make up the measures. These geological trends were then successfully used to adjust rock-types during reservoir modeling. Reservoir simulation was performed to understand the reservoir response to CO2 flooding and develop alternatives for sweep improvement. Continuous CO2 injection under certain alternate operations would help. The WAG process was effective in increasing the sweep efficiency of the reservoir for most of the cases studied by providing favorable mobility ratios and contacting more of the oil in the reservoir. The Gas-Assisted Gravity Drainage (GAGD) process was also evaluated. Solvent saturation profiles show that results are essentially consistent with the proposed GAGD theory. However, oil recovery was less than the best WAG cases, which is not surprising due to the high connate water saturation (0.56), relatively low thickness and lack of dip to the reservoir. Moreover, an increase in recovery could be realized more in the future for both the WAG and GAGD processes because CO2 contacted larger amounts of unswept oil in the reservoir compared to continuous CO2 flooding.
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Senocak, Didem, "Evaluation of sweep efficiency of a mature CO2 flood in Little Creek Field, Mississippi" (2008). LSU Master's Theses. 2486.
Hughes, Richard G.