Miscible or Near-Miscible Gas Injection, Which Is Better?

Thomas, F.B.; Holowach, Nancy; Zhou, Xuelong; Bennion, D.B.; Bennion, D.W.

doi:10.2523/27811-ms

Cited by 5 publications

(3 citation statements)

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“…Near-miscible gas drives appear more attractive compared to miscible gas drives, from both economic and operational standpoints. − A leaner injectant [lower liquefied petroleum gas (LPG) or natural gas liquid (NGL) enrichment in dry gas] is less expensive than a richer injectant. A lower pressure process also reduces costs because the injectant density is lower and costs of compression are reduced at near miscibility .…”

Section: Introductionmentioning

confidence: 99%

Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Fatemi

Sohrabi

2013

Energy Fuels

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Near-miscible gas injection represents a number of processes of great importance to reservoir engineers, including hydrocarbon gas injection and CO 2 flood. Very little experimental data is available in the literature on displacements involving very low interfacial tension (IFT). In this paper, we present the results of a series of two-and three-phase gas injection (drainage) and oil injection (imbibition) core flood experiments for a gas/oil system at near-miscible (IFT = 0.04 mN m −1 ) conditions. Two different cores, a high-permeability (1000 mD) and a lower permeability (65 mD) core, were used in the experiments, and both water-and mixed-wet conditions were examined. The results show that, despite a very low gas/oil IFT, there is significant hysteresis between the imbibition and drainage oil and gas relative permeability (k r ) curves in the 65 mD core. Hysteresis was less for the 1000 mD core (in comparison to the 65 mD core), but it still could not be ignored. Near-miscible k r hysteresis was significant for both water-and mixed-wet systems. The presence of immobile water in the water-wet cores improved oil relative permeabilities but reduced gas relative permeabilities in both imbibition and drainage directions. As a result, oil recovery for gas injection experiments improved when the rock contained immobile water. Both oil and gas relative permeabilities reduced when the rock wettability was altered to mixed-wet from water-wet, and as a result, oil recovery by gas injection in the mixed-wet rock was less than that obtained under water-wet conditions. We offer explanations for these observations based on our understanding of the pore-scale interactions and mechanisms, the distribution of fluid phases, and their spreading behavior. The results help us better understand the impact of some of the important parameters pertinent to k r and its hysteresis, especially in very low IFT gas/oil systems and mixed-wet rocks. Understanding these effects and behavior is important for the improved prediction of the performance of gas injection and water-alternating-gas (WAG) injection in oil reservoirs.

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Section: Introductionmentioning

confidence: 99%

Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Fatemi

Sohrabi

2013

Energy Fuels

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“…[16] Simulation studies have demonstrated that an injectant with less enrichment than that required for first-contact miscible with the oil often yields optimum oil recoveries owing to better sweep efficiencies in heterogeneous reservoir models. [30,31] Field-scale simulations show that near-miscible solvents are attractive because of improved sweep over miscible solvents. [32] Burger et al [30] showed that economically optimum enrichment in highviscosity-ratio secondary gas floods could be operated at pressures below the MMP.…”

Section: Introductionmentioning

confidence: 99%

“…[32] Burger et al [30] showed that economically optimum enrichment in highviscosity-ratio secondary gas floods could be operated at pressures below the MMP. Thomas et al [31] reported that gas-oil IFT can be reduced adequately under near-miscible conditions and that zero IFT is unnecessary for effective displacement processes in realistic porous media. Shyeh-Yung [33] demonstrated that tertiary gas flood recoveries below MMP do not decrease as severely as predicted by slim-tube tests for CO 2 .…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of simultaneous water and CO₂ (SWACO₂) injection for oil recovery in immiscible and near‐miscible conditions: A comparative study

2014

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A simultaneous water and CO2 injection to a dead crude oil has been performed on sandstone cores to evaluate oil recovery under secondary immiscible, secondary near‐miscible, tertiary immiscible, and tertiary near‐miscible injection modes. It is demonstrated that secondary SWACO2 injection as well as tertiary flood is an effective method for oil/residual oil recovery from oil‐saturated/water flooded porous media. In near‐miscible condition, oil recovery is higher than in immiscible condition because there is another active pore‐scale production mechanism in near‐miscible injection besides volumetric displacement mechanism. In secondary near‐miscible SWACO2 injection, the ultimate oil recovery increases by increasing SWAG ratio from 0.2 to 0.4 but due to some limits, e.g., topological effects, prohibiting contact of injected gas with residual oil in pores, altering SWAG ratio from 0.4 to 0.6 showed no essential effect on ultimate oil recovery. Secondary SWACO2 injection can recover higher fraction of oil than tertiary SWACO2 injection. This higher oil recovery results from the oil being more accessible by injected gas due to less water‐shielding effects. The results of this work can be helpful to better recognition and selection of gas‐based oil recovery methods to be implemented in depleted reservoirs.

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A Laboratory and Numerical Simulation Study of Co-optimizing CO2 Storage and CO2 EOR

Kamali

Hussain

Cinar

2014

SPE Asia Pacific Oil &Amp; Gas Conference and Exhibition

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This paper presents experimental observations that delineate co-optimization of CO2 EOR and storage. Pure supercritical CO2 was injected into a homogeneous, outcrop sandstone under various miscibility conditions. A mixture of hexane and decane was used for the oil phase. Three experiments were run at 70°C and different pressures (1,300, 1,700 and 2,100 psi). Each pressure was determined using a PVT simulator to create immiscible, near-miscible and miscible displacements. Oil recovery, differential pressure and compositions were recorded during experiments. A co-optimization function for CO2 storage and incremental oil was defined and calculated using the measured data for each experiment. A compositional simulator was then used to examine gravity effects on displacements and derive relative permeabilities. Experimental observations demonstrate that an almost similar oil recovery was achieved during miscible and near-miscible displacements whereas about 18% less recovery was recorded in the immiscible displacement. More decane was recovered in the miscible and near-miscible displacements than the immiscible displacement. The co-optimization function suggests that the CO2 storage efficiency was highest in the near-miscible displacement and that the near-miscible displacement displayed the best performance for coupling CO2 EOR and storage. Numerical simulations show that, even on the laboratory scale, there were significant gravity effects in the near-miscible and miscible displacements. It was revealed that the near-miscible and miscible recoveries depend strongly on the end-point CO2 relative permeability which increased with miscibility.

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Miscible or Near-Miscible Gas Injection, Which Is Better?

Cited by 5 publications

References 0 publications

Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Experimental investigation of simultaneous water and CO₂ (SWACO₂) injection for oil recovery in immiscible and near‐miscible conditions: A comparative study

A Laboratory and Numerical Simulation Study of Co-optimizing CO2 Storage and CO2 EOR

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Miscible or Near-Miscible Gas Injection, Which Is Better?

Cited by 5 publications

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Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-Miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis, and Permeability

Experimental investigation of simultaneous water and CO2 (SWACO2) injection for oil recovery in immiscible and near‐miscible conditions: A comparative study

A Laboratory and Numerical Simulation Study of Co-optimizing CO2 Storage and CO2 EOR

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Experimental investigation of simultaneous water and CO₂ (SWACO₂) injection for oil recovery in immiscible and near‐miscible conditions: A comparative study