Practical Metrics for Monitoring and Assessing the Performance of CO2-EOR Floods and CO2 Storage in Mature Reservoirs

Abstract

Monitoring an appropriate set of performance metrics is an essential part of a reservoir management strategy that seeks to maximize the efficiency of CO2-EOR floods, and benchmark the performance of the reservoir to other fields in the region. While a number of studies have outlined various options for evaluating the performance of the reservoir, many are not applicable to depleted oilfields that are commonly encumbered with limited data availability. As interest in CO2-EOR grows beyond giving new life to old fields, into a means of reducing anthropogenic CO2 emissions, metrics that enable the analyst to assess the storage capacity of the reservoir in addition to oil recovery efficiency have also become increasingly desirable. This paper will present a streamlined set of metrics that meet these objectives, along with their implementation in a dashboard-style presentation. These metrics provide complementary and non-redundant information, and crucially, are still applicable where a paucity of pressure data exists. The analyst is equipped with four groups of critical information. These are (A) flow rate and cumulative production data; (B) EOR performance trends (incremental oil recovery efficiency, CO2 storage efficiency, and net CO2 utilization factor); (C) operational performance trends (voidage replacement ratio and producing CO2-oil ratio); and (D) storage performance trends (incremental oil recovery factor vs. CO2 storage and CO2 storage capacity vs. voidage). To facilitate comparison, all metrics are normalized to percentage of original hydrocarbon pore volume (HCPV) injected. The utility of the selected set of metrics is demonstrated with data obtained from CO2-EOR activities in depleted oilfields of the Midwest Regional Carbon Sequestration Partnership (MRCSP) region. First, a nine-panel dashboard is populated using the metrics discussed for the D-33 reservoir, and will be shown to be useful in: quantifying CO2 storage capacity, highlighting reservoir performance parameters (CO2 breakthrough, oil recovery, voidage-related pressure changes during EOR etc.) and identifying CO2-flood maturity. Second, a four-panel dashboard is displayed as a comparative tool across all reservoirs in the region in order to highlight best and worst performing reservoirs and establish representative ranges for reservoir performance. Both dashboards will be useful when comparing performance against averages published in literature. This work's novelty is attributed to presenting an ideal set of performance metrics by streamlining the numerous options available. A unique dashboard-style presentation is suggested as a means of rapidly assessing oil recovery and CO2-storage performance, and collectively yielding useful insights.

Large CO2 Storage Volumes Result in Net Negative Emissions for Greenhouse Gas Life Cycle Analysis Based on Records from 22 Years of CO2-Enhanced Oil Recovery Operations

“…Together, these meters provide a comprehensive account of the CO 2 moving through EOR system operations . The metering data was used to calculate the mass of CO 2 purchased, mass of CO 2 produced with oil, CO 2 recycle, and CO 2 injected into the reservoirs.…”

“…Together, these meters provide a comprehensive account of the CO 2 moving through EOR system operations. 23 The metering data was used to calculate the mass of CO 2 purchased, mass of CO 2 produced with oil, CO 2 recycle, and CO 2 injected into the reservoirs. The cumulative net CO 2 stored associated with the EOR operations was based on methods for calculating the mass of CO 2 that remains in the reservoirs based on a net balance.…”

Assessment of CO2‐enhanced oil recovery and associated geologic storage potential in the Michigan Northern Pinnacle Reef Trend

“…As noted earlier (‘Analog‐based performance assessment’ section), the scaled performance metrics of interest for the monitored reefs are fractional primary recovery, f PR ; fractional incremental EOR recovery, f EOR ; net utilization ratio, UR; and storage efficiency factor, SEF. These are generally calculated directly from field data as part of reservoir surveillance . Following the practice of ARI, the metrics are calculated at a time that corresponds to 1.5 hydrocarbon pore volumes (HCPV) of CO 2 injection.…”

“…These are generally calculated directly from field data as part of reservoir surveillance. 16 Following the practice of ARI, 10 the metrics are calculated at a time that corresponds to 1.5 hydrocarbon pore volumes (HCPV) of CO 2 injection. When the data do not extend to 1.5 HCPV, either a simple trend is assumed to be valid for the performance metrics, or the functional forms suggested by Azzolina et al 17 are applied to these as the basis for extrapolation.…”