Wolfcamp A · 155 °F · JPSE 2021

How does gas composition change miscibility pressure?

Move ethane content in the composition planner and compare its interpolated miscibility pressure with the operating pressure you set.

Explore gas composition

gas MMPs measured: 4
OOIP, one 50/50 cycle: 23%
OOIP 50/50 ultimate: 36%
MMP shift, CH₄ to 50/50: −2,862 psi

Read the abstract

On Wolfcamp A sidewall cores at 155 °F and 5,000 psi, one huff-n-puff cycle recovered 23% OOIP with enriched gas (50% CH₄–50% C₂H₆) against 13% for 85/15, 9.7% for methane, and 9% for CO₂ — whose 5,000-psi performance fell below its own lower-pressure results. Ethane enrichment cut the CH₄ MMP from 5,715 to 2,853 psi. Foam co-injection with 50/50 gas recovered 19.2% in one cycle with the smallest CT disturbance of the series.

Prepared by Imad A. Adel

Definition. Enriched gas denotes produced gas whose ethane fraction is raised to lower the minimum miscibility pressure of the injection gas-oil system (JPSE 2021, 202: 108472).

Record status

6 records · 1 live model · 1 schematic

Reference	Record	Contents	Provenance
Fig. 5	MMP vs composition	Four measured minimum miscibility pressures.	Measured record
Table 4	Single-cycle results	Recovery and average CT change, six fluids.	Measured record
Table 4	Foam experiments	Two co-injection records and screening results.	Measured record
Live	Composition planner	Bounded interpolation over the measured axis.	Live calculation
S6	Enrichment ternary	Compositions are schematic; the readout is the measured minimum miscibility pressure.	Reference material Schematic

What's in this report

Publications

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 10.1016/j.petrol.2021.108472
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 10.2118/196019-MS

Measured basis · JPSE 2021 Fig. 5 · Measured record

MMP vs composition

Minimum miscibility pressure was measured for four injection fluids with Wolfcamp A oil at 155 °F.

Prepared by Imad A. Adel

Fig. 1 · MMP ladder

Wolfcamp A · 155 °F

What it showsFig. 1 — Minimum miscibility pressure by injection fluid. Red markers are the three methane–ethane measurements; the blue marker is CO₂, a separate fluid system. The dashed silver line is the 5,000 psi operating pressure of the huff-n-puff experiments; the shaded band marks pressures at or below the CO₂ minimum miscibility pressure, the lowest of the four fluids. All four values are from JPSE 2021 Fig. 5.

Complete figure data

Minimum miscibility pressure measurements at 155 °F.

Fluid	MMP (psi)	Source

CO₂ at 5,000 psi reached 21% ultimate — lower than its lower-pressure CO₂ experiments. Gas blockage of pore space was discussed as the cause. The low CO₂ MMP did not yield the highest recovery at 5,000 psi.

Single-cycle response · JPSE 2021 Table 4 · Measured record

Single-cycle huff-n-puff results

Recovery factor and average CT change were recorded after one cycle at 5,000 psi and 155 °F.

Prepared by Imad A. Adel

Fig. 2 · Recovery and CT response

one cycle · 5,000 psi

What it showsFig. 2 — One-cycle recovery factor is shown by red bars in the upper panel; average CT change is shown by grey markers in the lower panel, on the same fluid axis. Source: JPSE 2021 Table 4.

Complete figure data

One-cycle Wolfcamp A results at 5,000 psi and 155 °F.

Fluid	RF (% OOIP)	Avg CT change (HU)	Source

Highlighted row = highest one-cycle recovery of the series.

For the CH₄ enrichment series, recovery and average CT change increase from CH₄ through 85/15 to 50/50. CO₂ does not follow the trend (17 HU at 9% one-cycle RF). Foam rows are plug-referenced values; see Foam experiments.

Foam records · Wolfcamp A · JPSE 2021 · Measured record

Foam experiments

Foam was co-injected at 5,000 psi and 155 °F after surfactant screening at 3 gpt.

Prepared by Imad A. Adel

Foam-1 · surfactant + 85/15

Pressure	5,000 psi
Temperature	155 °F
Gas rate	13.9 ml/min
Solution rate	5.9 ml/min
Gas fraction	70%
RF, one cycle	12.8% OOIP
Foam collapse (normalized CT to zero)	about 48 h

Foam-2 · surfactant + 50/50

Pressure	5,000 psi
Temperature	155 °F
Gas rate	13.9 ml/min
Solution rate	5.9 ml/min
Gas fraction	70%
RF, one cycle	19.2% OOIP
Foam collapse (normalized CT to zero)	about 24 h

Surfactant screening · 3 gpt

Contact angle: 84.4° to 42.9°; screening result
IFT: 18.1 to 1.1; mN/m

Lifetime observations

Reported foam half-life at 5,000 psi: over 24 h (foam-2).

Normalized CT reached zero at about 48 h (foam-1) and 24 h (foam-2).

Foam-1 recovered 12.8% against 13% for its pure-gas pair. Residual oil remained in the glass-beads pack, so the plug-referenced recovery factor understates foam performance.

Evidence matrix · JPSE 2021 · Measured record

Cross-comparison

The matrix keeps one-cycle and ultimate recovery in separate columns.

Prepared by Imad A. Adel

Gas and foam comparison

Measured and reported outcomes for the six Table 4 fluids.

Fluid	MMP (psi)	RF, one cycle (%)	Avg CT change (HU)	RF, ultimate (%)	Cycles to ultimate	Source

Highlighted row = highest one-cycle recovery of the series.

Em dash = not reported. Foam-system MMP not measured; the carrier gas MMP appears in its own row.

Ultimate recovery records

Enriched 50/50 gas reached 36% OOIP after 5 cycles; more than 60% of the ultimate recovery was produced in the first cycle.

Related modeling work · SPE-196019

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

SPE-196019-MS · DOI 10.2118/196019-MS

Interactive model · measured compositions only · Live calculation

Composition planner

MMP is interpolated piecewise between the measured methane–ethane compositions. CO₂ remains a separate reference. The source reports one minimum miscibility pressure per fluid, so the planner resolves two regimes; the near-miscible band used elsewhere in the GEOR set is not defined for this fluid system.

Prepared by Imad A. Adel

Scenario controls

How to useSet the ethane fraction and the pressure; the readouts and Fig. 3 recompute.

Set composition. Choose an ethane fraction from 0% to 50%.
Set pressure. Choose the operating pressure and compare it with the interpolated MMP.
Save a case. Export a scenario, or import a prior text file to restore both controls.

Reading the chart: the open red marker is the composition you selected, placed on the interpolation line; the dashed silver line is the operating pressure you selected. The marker sitting on or below that line is the miscible condition. Hover for values; drag to zoom; use Reset axes in the figure toolbar, or double-click the plot.

C₂H₆ fraction (%)

Pressure (psi)

Fig. 3 · Composition planner15% C₂H₆ · 5,000 psi

Live outputsinterpolated between measured compositions

Interpolated MMP: 4,452.0 psi; piecewise linear
Regime: Miscible — multi-contact; regime code 1 = miscible · 0 = immiscible; 1
CO₂ reference MMP: 2,016 psi; separate fluid system

What it showsFig. 3 — Piecewise-linear MMP interpolation across the measured methane–ethane compositions. The open red marker is the selected composition; the dashed silver line is the selected operating pressure. CO₂ is excluded from this axis.

Complete figure data

Measured methane–ethane points and separate CO₂ reference.

Fluid basis	C₂H₆ (%)	MMP (psi)	Role
CH₄	0	5,715	measured axis point
85% CH₄–15% C₂H₆	15	4,452	measured axis point
50% CH₄–50% C₂H₆	50	2,853	measured axis point
CO₂	—	2,016	separate reference row

Model basis · equations and bounds · Live calculation

Model & equations

The planner contains one bounded interpolation. The CT equation is reproduced for interpretation of the reported CT response.

Prepared by Imad A. Adel

Equations

Normalized CT = (avg CT current − avg CT end) / (avg CT change)

Eq. 1

Normalized CT

JPSE Eq. 1.

MMP(x) = MMP_i + (MMP_i+1 − MMP_i) · (x − x_i) / (x_i+1 − x_i)

MMP interpolation

Applied piecewise to measured x = 0%, 15%, and 50% C₂H₆. The bound is x from 0% to 50%; no extrapolation is performed.

Assumptions and limits

Composition is expressed as the C₂H₆ volume fraction x on the measured CH₄–C₂H₆ axis.
Piecewise-linear interpolation is restricted to the measured compositions; CO₂ is a separate fluid system.
Regime is classified as immiscible below the interpolated MMP and miscible at or above it. The dataset reports one MMP per fluid, so no near-miscible band is resolved.
The composition and pressure control bounds, steps, and opening values are interface ranges, not data.
Gauge/absolute distinction (15 psi or less) is below the resolution of the reported values and is not reconciled.

Figures · JPSE 2021 Table 4 · Measured record

Foam vs pure gas in the fracture

The schematic contrasts the two fracture-filling behaviours behind the Table 4 CT record: foam holds the fracture volume, pure gas channels through it. Geometry is illustrative; the CT and recovery values driving the readout are measured.

Prepared by Imad A. Adel

Fracture sectionMeasured record

Injection progress

CT disturbance and one-cycle recovery from JPSE Table 4 at 5,000 psi: pure 50/50 gas 22 HU · foam-2 3 HU. Foam fills the fracture uniformly; pure gas channels through it.

Ethane enrichment on the pseudo-ternaryReference material

Composition schematic accompanying the 5,000 psi huff-n-puff experiments. Ethane enrichment moves the injection-gas marker toward the intermediates apex. The envelope and contact path are illustrative; they do not predict phase equilibrium or miscibility. The MMP readout uses the JPSE 2021 Fig. 5 measurements.

What it showsFig. 4 — Ethane enrichment moves the injection-gas marker toward the intermediates apex. The fixed envelope and contact path are schematic constructions, not measured compositions or phase-equilibrium results. The MMP readout is measured.

Reference · symbols and abbreviations · Reference material

Nomenclature

Symbols and abbreviations used in the report.

Prepared by Imad A. Adel

Symbols

Symbols used in the equations.

Symbol	Definition	Unit
x	Ethane fraction in the methane–ethane mixture	%
MMP	Minimum miscibility pressure	psi
CT	Computed-tomography attenuation	HU
RF	Recovery factor	% OOIP

Abbreviations

Abbreviations used in the report.

Abbreviation	Meaning
CH₄	Methane
C₂H₆	Ethane
CO₂	Carbon dioxide
HU	Hounsfield unit
OOIP	Original oil in place
gpt	Gallons per thousand (gallons of surfactant per 1,000 gallons of solution)
NGL	Natural gas liquids

How does gas composition change miscibility pressure?

Record status

What's in this report

MMP vs composition

Single-cycle results

Foam experiments

Cross-comparison

Composition planner

Model & equations

Publications

MMP vs composition

Fig. 1 · MMP ladder

Complete figure data

Single-cycle huff-n-puff results

Fig. 2 · Recovery and CT response

Complete figure data

Foam experiments

Foam-1 · surfactant + 85/15

Foam-2 · surfactant + 50/50

Surfactant screening · 3 gpt

Lifetime observations

Cross-comparison

Gas and foam comparison

Ultimate recovery records

Related modeling work · SPE-196019

Composition planner

Scenario controls

Complete figure data

Model & equations

Equations

Assumptions and limits

Foam vs pure gas in the fracture

Fracture sectionMeasured record

Ethane enrichment on the pseudo-ternaryReference material

Nomenclature

Symbols

Abbreviations