Gas EOR Project · Texas A&M University
CO2, rich-gas, foam, and hybrid huff-n-puff corefloods on Eagle Ford and Wolfcamp plugs at reservoir temperature and pressure, monitored by time-lapse computed tomography. Combined gas and surfactant recovery reached 57.6% OOIP in a single plug.
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Organic-rich shale formations recover less than 10% of original oil in place under primary depletion. Production declines rapidly, and thousands of wells drilled in formations with high remaining oil saturation present a target for enhanced oil recovery. The Eagle Ford and Wolfcamp campaigns summarized here address that target with gas injection: huff-n-puff corefloods at reservoir temperature and pressure, monitored by time-lapse computed tomography to track fluid movement inside the core plugs.
Recovery in these systems is governed by the interaction between fluids in the fracture network and oil stored in the matrix. Above the minimum miscibility pressure, a multi-contact vaporizing gas drive extracts light and intermediate components from the larger pores, and recovery factor continues to rise with operating pressure beyond the MMP. Surfactant-assisted spontaneous imbibition acts on the smaller pores through wettability alteration and interfacial-tension reduction, and enriched produced gas (50% CH4–50% C2H6) extends the method to fields where CO2 supply or flaring constraints govern. The two mechanisms are complementary, and their combination defines the hybrid scheme.
Interactive scene requires WebGL.Miscible — multi-contact · 17% OOIP
Miscibility develops by contact, not on injection. The injected gas vaporizes light and intermediate components from the oil it meets; the enriched gas moves ahead and contacts fresh oil, and each contact moves the gas composition toward the critical mixture. Above the minimum miscibility pressure the two-phase region has contracted enough for the contact path to reach a single phase, and the displacement becomes piston-like at the front. Below it the path ends on a tie line and the front stays two-phase, leaving bypassed oil behind.
The core plugs carry two pore classes that respond to different agents. Gas extracts oil from the larger pores, where the CT number falls as density falls. Aqueous surfactant solution imbibes counter-currently into the smaller pores under wettability alteration and interfacial-tension reduction, and the CT number rises. The hybrid scheme applies the two agents in sequence to the two classes.
Miscible — recovery rising with pressure toward 50% OOIP
Anchors: MMP 2,132 psig · RF < 5% OOIP below MMP · RF 50% OOIP at 3,500 psig · Eagle Ford CO2 huff-n-puff dataset
Miscible — recovery rising with pressure toward 50% OOIP
Light and intermediate components extracted from larger pores — up to 50% OOIP
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Interactive reports
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Slim tube and huff-n-puff · Interactive report
Slim-tube determination of the CO2–crude MMP (2,132 psig, Eagle Ford) using a 20-ft fast-slim-tube protocol, and huff-n-puff corefloods showing that recovery factor continues to increase as operating pressure is raised beyond the MMP — behavior opposite to conventional reservoirs. Operating below the MMP yields recovery factors under 5% OOIP.
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Gravity drainage · Interactive report
Slim-tube, bead-pack, and reservoir-core experiments across immiscible, near-miscible, and miscible conditions isolate the contribution of gravity drainage during CO2 flooding. Vertically stable downward displacement outperformed horizontal displacement, indicating gravity drainage carries greater significance than phase behavior alone.
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Gas composition and foam · Interactive report
Wolfcamp core experiments compare methane, ethane-enriched gas, carbon dioxide and foam. Inspect the measured recovery results, then use the composition planner within its stated interpolation range.
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Hybrid gas and surfactant · Interactive report
CO2 huff-n-puff recovered up to 49% OOIP from Eagle Ford cores; surfactant-assisted spontaneous imbibition added between 5.2 and 11.6 percentage points — including from a plug that had produced under 1% under gas injection — and the maximum combined recovery observed in a single plug was 57.6% OOIP.
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