Impact of Sub-core-scale Heterogeneity on Meter-Scale Flow and Brine Displacement in Drainage by CO2

Z. Moreno, A. Rabinovich

Research output: Contribution to journalArticlepeer-review

Abstract

Studies of CO2-brine two-phase flow are predominantly carried out on core samples or reservoir-scale domains. In this work we investigate intermediate-scale flow considering a cubic rock with 1 m3 volume incorporating sub-core (mm)-scale heterogeneity. First, a coreflooding experiment is analyzed to estimate subcore permeability spatial distribution and the results are used as input into the meter-scale model without any upscaling required. High-resolution numerical simulations are conducted to model CO2 injection into a brine saturated rock. We find significant differences between the meter-scale rock simulation and core experiment saturation distributions resulting from highly influential boundary effects on the core scale and pronounced gravity impact on the meter scale. A detailed analysis of flow and brine trapping in rock simulations is presented considering different flow models and permeability structures. It is shown that gravity and capillary heterogeneity have substantial impact on the saturation in the deeper regions, which exhibit sufficiently low capillary pressure, and these regions also show increased trapping of brine. Two trapping mechanisms are discussed: Type I which is a result of entry pressure considerations and Type II, which occurs due to lack of CO2 connectivity. The two types of trapping are found to be correlated to the permeability structure. A formula is presented relating between trapping and permeability statistical parameters, that is, variance of log-permeability and correlation length scale, as well as to the Bond number characterizing the ratio between gravity and capillary effects.

Original languageEnglish
Article numbere2020WR028332
JournalWater Resources Research
Volume57
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • CO storage
  • CO-brine flow
  • capillary trapping
  • meter scale
  • permeability statistics
  • subcore heterogeneity

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