Effects of Gravity and Viscous Crossflow on Hydrocarbon Miscible Flood Performance in Heterogeneous Reservoirs

Pande, Karan

doi:10.2118/24935-ms

Cited by 36 publications

(14 citation statements)

References 16 publications

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“…1.48). Channeling occurs only when the 85 percent enriched gas and three-point weighting is used because the denser gas reduces gravity crossflow to the top lower permeability layers (these results are similar to Pande (1992).…”

Section: Resultssupporting

confidence: 61%

Development of More-Efficient Gas Flooding Applicable to Shallow Reservoirs

Rossen¹,

Johns²,

Pope³

2003

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ABSTRACT:The objective of this research is to widen the applicability of gas flooding to shallow oil reservoirs by reducing the pressure required for miscibility using gas enrichment and increasing sweep efficiency with foam. Task 1 examines the potential for improved oil recovery with enriched gases. Subtask 1.1 examines the effect of dispersion processes on oil recovery and the extent of enrichment needed in the presence of dispersion. Subtask 1.2 develops a fast, efficient method to predict the extent of enrichment needed for crude oils at a given pressure. Task 2 develops improved foam processes to increase sweep efficiency in gas flooding. Subtask 2.1 comprises mechanistic experimental studies of foams with N 2 gas. Subtask 2.2 conducts experiments with CO 2 foam. Subtask 2.3 develops and applies a simulator for foam processes in field application.Regarding Task 1, significant research was accomplished in the last three and one-half years with over 11 journal and conference publications, many of which have been repeatedly referenced by other researchers. All goals, except one, were accomplished for both Task 1.1 and Task 1.2. The remaining goal on the development of accurate CO 2 MMP correlations is near completion and will be published in a future paper. Task 1.1 focused on the effect of dispersive processes on oil recovery and how to enrich gas so that the MMP can be reduced. Simulation studies (Solano et al., 2001; 4 Stalkup, 1990) show that oil recovery for enriched gas drives depends on the amount of dispersion in reservoir media, but the value of dispersion, expressed as dispersivity, at the field scale, is unknown. This research investigated three types of dispersion in permeable media to obtain realistic estimates of dispersive mixing at the field scale. These types are echo dispersivity, which is unaffected by fluid flow direction, transmission dispersivity, which is caused by layering in permeable media, and local dispersivity, which is the mixing observed at a point in the reservoir as tracer flows past.We analyzed a collection of single-well tracer test (SWTT) data to estimate echo dispersivity at the SWTT scale. The estimated echo dispersivities closely match a published trend with length in dispersivities obtained from groundwater tracer tests. This unexpected result-it was thought that transmission dispersivity should be greater than echo dispersivity-is analyzed with numerical simulation. The agreement between the SWTT echo dispersivities and the field trend suggests that the field data are measuring local dispersivities, which are on the order of 2 ft. All dispersivities appear to grow with length.The interaction of phase behavior and flow, in the presence of dispersive mixing, was examined for 1-D four-component and twelve-component enriched-gas displacements. Numerical and analytical solutions demonstrated that oil recovery may be substantially increased by gas enrichment above the minimum enrichment for miscibility (MME). For the twelve-component oil, the increase in recovery (displ...

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Section: Resultssupporting

confidence: 61%

Development of More-Efficient Gas Flooding Applicable to Shallow Reservoirs

Rossen¹,

Johns²,

Pope³

2003

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“…Field-scale simulations show that near-miscible solvents are attractive because of improved sweep over miscible solvents (Pande 1992). Burger et al (1994) showed that economically optimum enrichment in high-viscosity-ratio secondary gas floods could be operated at pressures below the MMP.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Mechanisms of Oil Recovery By Near-Miscible Gas Injection

et al. 2007

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As gas flooding becomes a more viable means of enhanced oil recovery, it is important to identify and understand the pore-scale flow mechanisms, both for the development of improved gas flooding applications and for the predicting phase mobilisation under secondary and tertiary gas flooding. The purpose of this study was to visually investigate the pore-level mechanisms of oil recovery by near-miscible secondary and tertiary gas floods. High-pressure glass micromodels and model fluids representing a near-miscible fluid system were used for the flow experiments. A new pore-scale recovery mechanism was identified which significantly contributed to oil recovery through enhanced flow and cross-flow between the bypassed pores and the injected gas. This mechanism is strongly related to a very low gas/oil interfacial tension (IFT), perfect wetting conditions and simultaneous flow of gas and oil in the same pore, all of which occur as the gas/oil critical point is approached. The results of this study helps us to better understand the pore-scale mechanisms of oil recovery in very low-IFT (near-miscible) systems. In particular we show that in near-miscible gas floods, behind the main gas front, the recovery of the oil continues by cross-flow from the bypassed pores into the main flow stream and as a result almost all of the oil, which has been contacted by the gas, could be recovered. Our observations in high-pressure micromodel experiments have demonstrated that this mechanism can only occur in near-miscible processes (as opposed to immiscible and completely miscible processes), which makes oil displacement by near-miscible gas floods a very effective process.

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“…Field-scale simulations show that near-miscible solvents are attractive because of improved sweep over miscible solvents (Pande 1992). Burger et al (1994) showed that economically optimum enrichment in high-viscosity-ratio secondary gasfloods could be operated at pressures below the MMP.…”

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confidence: 99%

Visualisation of Residual Oil Recovery by Near-miscible Gas and SWAG Injection Using High-pressure Micromodels

2008

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We present results of high-pressure micromodel visualizations of pore-scale fluid distribution and displacement mechanisms during the recovery of residual oil by nearmiscible hydrocarbon gas and SWAG (simultaneous water and gas) injection under conditions of very low gas-oil IFT (interfacial tension), negligible gravity forces and water-wet porous medium. We demonstrate that a significant amount of residual oil left behind after waterflooding can be recovered by both near-miscible gas and SWAG injection. In particular, we show that in both processes, the recovery of the contacted residual oil continues behind the main gas front and ultimately all of the oil that can be contacted by the gas will be recovered. This oil is recovered by a microscopic mechanism, which is strongly linked to the low IFT between the oil and gas and to the perfect spreading of the oil over water, both of which occur as the critical point of the gas-oil system is approached. Ultimate oil recovery by near-miscible SWAG injection was as high as near-miscible gas injection with SWAG injection using much less gas compared to gas injection. Comparison of the results of SWAG experiments with two different gas fractional flow values (SWAG ratio) of 0.5 and 0.2 shows that fractional flow of the near-miscible gas injected simultaneously with water is not a crucial factor for ultimate oil recovery. This makes SWAG injection an attractive IOR (improved oil recovery) process especially for reservoirs, where continuous and high-rate gas injection is not possible (e.g. due to supply constraint).

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Effects of Gravity and Viscous Crossflow on Hydrocarbon Miscible Flood Performance in Heterogeneous Reservoirs

Cited by 36 publications

References 16 publications

Development of More-Efficient Gas Flooding Applicable to Shallow Reservoirs

Development of More-Efficient Gas Flooding Applicable to Shallow Reservoirs

Microscopic Mechanisms of Oil Recovery By Near-Miscible Gas Injection

Visualisation of Residual Oil Recovery by Near-miscible Gas and SWAG Injection Using High-pressure Micromodels

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