(559o) Investigations on Petrophysical Property Alterations Induced By CO2 Injection into Sandstone Reservoirs

The objective of this work is to investigate variations in petrophysical properties that may be caused by CO₂ injection activities in a partially-depleted oil reservoir. A field-scale numerical simulation model is established to study the Upper Pennsylvanian Morrow B sandstone formation. The reservoir model is employed to examine the CO₂ dissolution inthe aqueous phase and the chemical interaction of reservoir minerals. The reactive fluid transportation model is competent to evaluate the field’s potential for long-term CO₂ sequestration, and investigate the impact of the CO₂ injection on petrophysical properties of the Morrow B formation, including pore fluid composition, mineralogy, porosity and permeability.

A field-scale reservoir model is structured utilizing a compositional simulator. Extensive field data collected from Morrow B formation are involved, including well log data, core analysis data, 3D seismic survey data, fluid properties and engineering design parameters. The reservoir model is tuned via a rigorous history matching study using available field CO₂-WAG flooding data. The history-matched model is employed to assess the multiple trapping mechanisms including residual trapping, solution trapping and mineral trapping. The numerical experiments are conducted by considering the intra-aqueous and mineral dissolution/precipitation reactions, which may promote pore structure alterations. Moreover, we take advantage of Kozeny–Carman model to calculate the resistance factor and estimate the permeability changes. The reservoir is monitored for 1000 years after all the injectors and producers are shut-in to investigate the long-term impact of CO₂ injection to the petrophysical properties of the field.

The study is anticipated to confirm the changes in Morrow B petrophysical properties observed from the laboratory chemo-mechanical responses and show optimum amount of CO₂ storage potential within the Farnsworth Unit. The results of this work indicate that: (1) dissolution of authigenic carbonate minerals enhances porosity in calcite-dominated regions, (2) permeability enhancement is observed in areas with high dissolution, (3) amounts of dissolution/precipitation of the principal accessory minerals evolves through time.

In this work, we successfully establish a robust and well-validated field scale CO₂ injection reservoir model that comprehensively couples the complex fluid transportation mechanisms with considerations of chemical reactions. Observations and results generated from the numerical simulation model provide valuable insight regarding the petrophysical properties alterations induced by the CO₂ injection activities. The study may serve as a benchmark case for future CO₂ EOR projects when reactive transportations are considered.