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Hybrid CO2 and chemical recovery · Eagle Ford cores

What does surfactant imbibition add after CO2 huff-n-puff?

Four Eagle Ford core plugs ran CO2 huff-n-puff at 1,400–3,500 psig and then surfactant-assisted spontaneous imbibition. Gas recovery reached 49% OOIP at 3,500 psig and SASI added a further 8.6%, totaling 57.6%; the plug operated below the MMP produced under 1% from gas but 8.7% from SASI. The two mechanisms act on different pore classes and their contributions are complementary, not additive constants.

Open hybrid recovery planner
core plugs
4
OOIP maximum combined
57.6%
gas RF below MMP
< 1%
of ultimate in cycle 1
41–67%
Definition. Surfactant-assisted spontaneous imbibition (SASI) recovers oil by counter-current imbibition of an aqueous surfactant solution, acting through wettability alteration and interfacial-tension reduction (SPE-191502).

Record status

provenance by plug

Measured values are stated in the source text. Digitized values are read from the published figures. Derived values are per-plug sums of reported or digitized component values and are not reported as totals in the source.

What's in this report

Publications

  1. Zhang, F., Adel, I.A., Park, K.H., Saputra, I.W.R., and Schechter, D.S. 2018. Enhanced Oil Recovery in Unconventional Liquid Reservoir Using a Combination of CO2 Huff-n-Puff and Surfactant-Assisted Spontaneous Imbibition. SPE-191502-MS, SPE Annual Technical Conference and Exhibition, Dallas, Texas, 24–26 September. DOI
  2. Adel, I.A., Tovar, F.D., Zhang, F., and Schechter, D.S. 2018. The Impact of MMP on Recovery Factor During CO2–EOR in Unconventional Liquid Reservoirs. SPE-191752-MS, SPE Annual Technical Conference and Exhibition, Dallas, Texas, 24–26 September. DOI
  3. Zhang, F., Adel, I.A., Saputra, I.W.R., Chen, W., and Schechter, D.S. 2019. Numerical Investigation to Understand the Mechanisms of CO2 EOR in Unconventional Liquid Reservoirs. SPE-196019-MS, SPE Annual Technical Conference and Exhibition, Calgary, Alberta, 30 September–2 October. DOI
  4. Zhang, F., Adel, I.A., Saputra, I.W.R., and Schechter, D.S. 2019. Numerical Investigation of EOR Applications in Unconventional Liquid Reservoirs through Surfactant-Assisted Spontaneous Imbibition (SASI) and Gas Injection Following Primary Depletion. SPE-196055-MS, SPE Annual Technical Conference and Exhibition, Calgary, Alberta, 30 September–2 October. DOI
  5. Zhang, F., and Schechter, D.S. 2021. Gas and Foam Injection with CO2 and Enriched NGL's for Enhanced Oil Recovery in Unconventional Liquid Reservoirs. Journal of Petroleum Science and Engineering 202: 108472. DOI

SPE-191752 supplies the Eagle Ford huff-n-puff pressure series; the 2021 journal article supplies the Wolfcamp A ultimate point.

Core data · records · digitized from published figures

Core records

The selector isolates one plug record and its cumulative gas-recovery sequence.

Prepared by Imad A. Adel

Selected core

SPE-191502
Selected-core cycle plateausdigitized from Figs. 2–3

What it showsFigure 1. Cumulative gas recovery for the selected core. The reported points are production plateaus digitized from SPE-191502 Figs. 2–3.

Identity and recovery

Selected core identity and recovery values
ParameterValueSource status
SPE-191752 reports 49.31% for the same 3,500-psig experiment; SPE-191502 rounds to 49%.

Cycle plateau dataset

Selected core cycle plateau dataset
CycleCumulative gas RF (% OOIP)Source
Core data · cycle dynamics · digitized from published figures

Cycle dynamics

Cumulative gas-recovery plateaus are compared at the same cycle number without extending a core beyond its last reported plateau.

Prepared by Imad A. Adel

Cycle lookup

16
All-core production sequencesSPE-191502 Figs. 2–3

What it showsFigure 2. Cumulative gas recovery by cycle for the four Eagle Ford plugs, digitized from SPE-191502 Figs. 2–3. The first cycle produced 41–67% of each plug's own ultimate, the per-cycle increment declined, and the sequences leveled off; fresh CO2 was injected each cycle.

CORE4 ran three cycles; oil was produced only in cycles 1 and 2. A dash is shown beyond its last reported production plateau.

Cycle plateau dataset

Complete cycle plateau dataset for all cores
CoreCycle 1Cycle 2Cycle 3Cycle 4Cycle 5Cycle 6
Core data · aqueous stage · contains derived sums

SASI contribution

Per-plug gas recovery and the subsequent SASI increment are kept as separate measured contributions.

Prepared by Imad A. Adel

Gas and SASI recovery shares

SPE-191502

Figure 3. Gas recovery is shown in red and the subsequent SASI increment in blue. Combined totals are per-plug sums; tags above the bars distinguish reported text from derived sums.

Gas and SASI contributions for all cores
CoreGas RF (%)SASI (%)Combined (%)Status

Foam appeared in the graduated cylinder early in SASI after CO2 huff-n-puff; CO2 had adsorbed or penetrated the plugs. CORE4's SASI share dominated its total. The SASI contribution was measured over approximately 240–300 h.

Core data · pressure dependence · reported measured values

Pressure dependence

Eagle Ford huff-n-puff recovery increased across the reported pressure series; the separate Wolfcamp A point uses a different rock and oil.

Prepared by Imad A. Adel

CO2 huff-n-puff recovery

170 °F · Eagle Ford MMP 2,132 psig

Figure 4. Eagle Ford experiment ultimates are connected across 1,450–3,500 psig. The open square is Wolfcamp A · ultimate · JPSE Fig. 11, labeled 5,000 psi (as published, JPSE); it is not joined to the Eagle Ford line. The dashed line marks the Eagle Ford MMP at 2,132 psig and the shaded band spans the near-miscible regime from 2,132 to 2,399 psig; pressures at or above 2,400 psig are miscible. The below-MMP gas result establishes the basis for a subsequent SASI stage.

Complete pressure response dataset
Rock/oil systemPressureRF (% OOIP)Source

Eagle Ford values are as tabulated in the source figure. The Wolfcamp A result is an ultimate value for a different rock and oil.

Related modeling work

SPE-196055SASI and gas injection sequencing after primary depletion; a core-scale history match carried into a hydraulically fractured well model with realistic fracture geometry and conductivity. DOI

SPE-196019CT-derived core-scale model; primary mechanisms multi-contact miscibility and vaporizing gas drive; diffusion minor; ternary-diagram analysis; upscaled dual-porosity compositional field model. DOI

Interpretation · matrix · contains derived sums

Cross-comparison

The measured and derived fields are aligned by plug without normalizing pressure or cycle count.

Prepared by Imad A. Adel

Core comparison matrix

SPE-191502
Cross-comparison of four hybrid recovery cores
CorePressure (psig)CyclesGas RF (%)SASI (%)Combined (%)Sources
Shaded row: CORE3, the plug with the highest combined recovery
Interpretation · interactive planner · interpolated scenario output

Hybrid planner

The gas envelope is the piecewise-linear interpolation of the Eagle Ford huff-n-puff dataset.

Prepared by Imad A. Adel

Scenario controls

How to useSet a pressure and a SASI increment; the readouts and the figure recompute.
  1. Set a pressure inside the measured Eagle Ford span of 1,450 to 3,500 psig.
  2. Set a SASI increment inside the 5.2 to 11.6 percentage-point range reported or digitised across the four plugs.
  3. Read the interpolated gas recovery and the scenario sum; the sum is not a prediction outside these bounds.

Reading the chart: the red envelope is the piecewise-linear interpolation of the five measured Eagle Ford points. The open circle marks the interpolated gas recovery at the selected pressure. The blue vertical segment above it is the selected SASI increment, so the top of the segment is the scenario sum. The dashed line at 2,132 psig is the Eagle Ford MMP and the shaded band spans the near-miscible regime up to 2,400 psig.

1,4503,500 psig
5.211.6%
Gas envelope and scenariowithin measured span only
Gas RF
31.03%
piecewise interpolation
SASI increment
8.6%
scenario input
Scenario combined recovery
39.63%
scenario sum — recorded combined values ranged 9.6–57.6%
Pressure regime
Miscible
at or above 2,400 psig

What it showsFigure 5. The red curve is the piecewise-linear gas envelope. The open scenario marker gives the interpolated gas value; the blue vertical segment adds the selected SASI increment to the scenario sum.

Envelope and scenario dataset

Gas envelope dataset and current scenario values
RecordPressure (psig)Gas RF (%)SASI (%)Combined (%)
Shaded row: current scenario
Interpretation · model

Model & equations

The planner applies a bounded interpolation and a per-plug recovery sum; it does not recompute a compositional or fracture-scale model.

Prepared by Imad A. Adel

Governing equations

Piecewise-linear gas recovery
Eq. 1
RFgas(P) = RFi + (P − Pi) · (RFi+1 − RFi) / (Pi+1 − Pi)
Applied between adjacent HNP_EF measurements from 1,450 to 3,500 psig inclusive. No extrapolation is performed.
Combined-recovery definition
Eq. 2
RFcomb = RFgas + RFSASI
A per-plug sum of reported or digitized component values, where RFSASI is the recovery increment contributed by the aqueous stage on that plug. It is not a universal additive constant.

Assumptions and bounds

  1. The HNP_EF pressure-response points are experiment ultimates as tabulated in SPE-191752 Fig. 9.
  2. Linear interpolation is restricted to adjacent measured points from 1,450 to 3,500 psig.
  3. Two pressure spans coexist. The four core plugs span 1,400–3,500 psig; the HNP_EF pressure-response series spans 1,450–3,500 psig. CORE4 sits at 1,400 psig, below the interpolation floor, so the planner does not reproduce that plug.
  4. The selected SASI increment is restricted to the measured 5.2–11.6 percentage-point range; it does not represent a pressure correlation.
  5. The combined result is a plug-scale scenario sum. Matrix heterogeneity, fracture geometry, soak time, and fluid-contact differences are outside this calculation.
  6. The slider ranges, steps, and defaults are interface ranges, not data.
  7. The pressure regimes are read against the Eagle Ford MMP of 2,132 psig: immiscible below 2,132 psig, near-miscible from 2,132 to 2,399 psig, miscible at or above 2,400 psig.
  8. The gauge/absolute distinction (at or below 15 psi) is below the resolution of the reported values and is not reconciled.
Figures · huff-n-puff cycle · digitized from published figures

Schematic

The schematic steps through the inject, soak, and produce phases of one huff-n-puff cycle on a fractured plug. It is a diagram of the reported sequence, not a simulation.

Prepared by Imad A. Adel

CO2 huff-n-puff cycle

Selected cycle
Cycle 3 of 6
Phase
INJECT

Cycle plateaus are the measured Core 3 values at 3,500 psig, digitized from SPE-191502 Fig. 3a (25.8 to 49.3% OOIP over six cycles).

Schematic pressure–time trace of one huff-n-puff cycle: injection to the working pressure, soak at constant pressure, production drawdown.

Figure 6. Schematic of one CO2 huff-n-puff cycle on a fractured Eagle Ford plug. Cycle plateaus driving the saturation readout are the measured CORE3 values at 3,500 psig, digitized from SPE-191502 Fig. 3a (25.8 to 49.3% OOIP over six cycles).

Reference · nomenclature

Nomenclature

Symbols and abbreviations used in the report.

Prepared by Imad A. Adel

Symbols

Symbols
SymbolDefinitionUnit
PPressurepsig
RFgasCO2 huff-n-puff recovery factor% OOIP
RFSASIRecovery increment contributed by the SASI stage% OOIP
RFcombCombined gas and SASI recovery factor% OOIP
RFiGas recovery factor at the bracketing measured pressure% OOIP

Abbreviations

Abbreviations
TermDefinition
CO2Carbon dioxide
HNPHuff-n-puff
MMPMinimum miscibility pressure
OOIPOriginal oil in place
SASISurfactant-assisted spontaneous imbibition