Immiscible WAG Injection in the Fensfjord Formation of the Brage Oil Field

Skauge, Arne; Berg, Erik

doi:10.3997/2214-4609.201406788

Cited by 9 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[110][111] Simulation studies have shown larger three-phase zones. [112][113][114][115][116] It has been shown that the three-phase relative permeability is significantly different from the two-phase relative permeability. The relative permeabilities of the injected fluids, gas and water, is reduced in the three-phase zone.…”

Section: Impact Of Three-phase Characteristics and Capillary Pressurementioning

confidence: 99%

Progress in Immiscible WAG Modelling

Skauge¹,

Dale

2007

All Days

Self Cite

View full text Add to dashboard Cite

The paper reviews recent development in modelling of immiscible WAG processes (IWAG). Several different approaches have been made to model three-phase relative permeability in particular. In most cases capillary pressure has been neglected in application of these models in numerical simulations of IWAG. The argument behind eliminating capillary pressure is to simplify the model, and the assumption that capillary pressure is of less importance for the problem analysed or because there are no experimental data available. This study also shows the consequence of neglecting capillary pressure. A novel approach to include three-phase capillary pressure is discussed, and also a procedure for estimation of three-phase capillary pressure from more available two-phase capillary pressure data. A practical case study of history matching IWAG core floods is also presented. Introduction Numerical simulation of any EOR process is a key to the prediction of incremental oil recovery. Water -alternating -gas (WAG) injection has found an increasing application in both clastic and carbonate reservoirs and at both miscible and immiscible gas conditions 1,2. The addition oil recovery is typically in the range of 5–10 percent of the original oil in place. WAG injection is an oil recovery method initially aimed to improve sweep during gas injection. Possible improved microscopic efficiency in three-phase zones of the reservoir may come as an added benefit from the WAG injection. Today the WAG process (both miscible and immiscible) is considered for a number of new fields in the North Sea. WAG is defined as any injection of both water and gas into the same reservoir. This including definition covers MWAG (miscible), IWAG (immiscible), HWAG (hybrid), SWAG (simultaneous), and also tertiary gas injection or tertiary water flooding. When miscibility is developed along the gas slug, as gas displaces oil, it is referred to as a miscible WAG. In this case the main purpose of the water slug is to increase the volumetric sweep since the residual oil saturation will be low after the miscible front has passed. Immiscible WAG (IWAG) is pulses of gas and water injected, where the gas cannot develop miscibility with oil. Still some compositional exchanges between gas and oil may be important for the fluid characterization and oil recovery. Hybrid WAG is when a large slug of gas is injected followed by a number of small slugs of water and gas. Simultaneous injection has also been performed, but is reported to give reduced injectivity in some cases. In this paper immiscible WAG processes will be discussed. This process involves both drainage and imbibition processes, three phase flow modelling approach, and hysteresis in relative permeabilities and capillary pressure. The complexity of the WAG process is further complicated by mass exchanges (swelling and stripping of the oil by the injected gas). The focus is here on fluid flow functions and the mass exchanges are here ignored. Simulation studies of IWAG3–7 have shown that analytical models like Stone 8 and Jenkins 9 may strongly underestimate the extent of the three-phase zone. The extent of the three-phase zone is influenced by phase trapping and three-phase relative permeabilities, see Figure 1. The residual oil saturation in the three-phase zone may also be reduced compared to two-phase flow, due to effect of trapped gas on residual oil and also three-phase relative permeabilities 10–12. Experimental studies showed accelerated oil production and higher core flood oil recovery as a result of three-phase flow 10–13. The oil recovery has been related to the trapped gas saturation 11–13, and the influence of the effect of trapped gas is found to be varying with core wettability 13. Experimental results have also shown that both gas and water relative permeability may be reduced during three-phase flow. Simulation results have shown that the two-phase relative permeability hysteresis models were unable to describe the three phase experiments. The match of WAG experiments was improved by the three-phase relative permeability approach 14,15.

show abstract

Section: Impact Of Three-phase Characteristics and Capillary Pressurementioning

confidence: 99%

Progress in Immiscible WAG Modelling

Skauge¹,

Dale

2007

All Days

Self Cite

View full text Add to dashboard Cite

show abstract

“…[1][2][3][4] WAG has, in most cases, been implemented at a later stage of production as an improved recovery process after a long period of water injection. [1][2][3][4] WAG has, in most cases, been implemented at a later stage of production as an improved recovery process after a long period of water injection.…”

Section: Introductionmentioning

confidence: 99%

Gas Segregation During WAG Injection and the Importance of Parameter Scaling in Three-Phase Models

Hustad¹,

Trygve²,

Lerdahl³

et al. 2002

Proceedings of SPE/DOE Improved Oil Recovery Symposium

View full text Add to dashboard Cite

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSaturation histories from simulations on a mesoscopicscale heterogeneous model at immiscible and miscible conditions are compared with emphasis on gas segregation. Selected models for three-phase flow, and scaling of the end point saturations, relative permeabilities, and capillary pressures have been applied. The flow parameters of the facies were obtained from pore scale network modeling with input from North Sea sandstones. The simulation cases included water, gas, and water-alternating-gas (WAG) injection.Gas injection at irreducible water saturation demonstrates stronger gas segregation as the pressure exceeds the minimum miscibility pressure (MMP). Gas segregation is not so evident at the mesoscopic scale during WAG injection. High water saturation in the set-planes hampers the vertical gas flow. A bank of high oil saturation forms in front of the advancing gas at miscible conditions. Oil segregates to the set-plane below and the water cycle that follows mobilizes the accumulated oil.

show abstract

“…In some North Sea oil reservoirs, produced hydrocarbon gas has been re-injected in water injection wells with the purpose to improve oil recovery and reducing gas export [1][2][3][4][5][6][7][8] . The hydrocarbon gas has been either near miscible [4][5][6] or immiscible WAG [1][2][3]7,8 when contacted with the oil in the reservoir.…”

Section: Introductionmentioning

confidence: 99%

“…The hydrocarbon gas has been either near miscible [4][5][6] or immiscible WAG [1][2][3]7,8 when contacted with the oil in the reservoir. The availability of produced hydrocarbon gas has encouraged use of WAG processes in North Sea oil reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Simulation of the Immiscible WAG Process Using Cycle-Dependent Three-Phase Relative Permeabilities

Larsen

Skauge

1999

Proceedings of SPE Annual Technical Conference and Exhibition

View full text Add to dashboard Cite

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractOil recovery by immiscible WAG is dependent on the saturation cycles that occur in a core-flood or in the reservoir. For the reservoir case, segregation of gas and water can generate other saturation cycles than in a core-flood. In order to predict WAG behavior in the reservoir from experimental results, numerical models with an effective hysteresis description of the three-phase oil, water and gas relative permeabilities should be considered.There has earlier been developed a methodology that accounts for both three-phase flow effects and hysteresis effects in numerical simulations of the immiscible WAG process. Simulation studies have shown how three-phase flow description may influence the choice of drive mechanisms and also the design of a WAG process. Furthermore, a principal component analysis (PCA) is conducted on the simulation model that is consistent with the experimental data. The results from the PCA showed how the hysteresis parameters in the simulation model may be correlated to the physical system. The PCA analysis describe how the three-phase effects in water and gas relative permeabilities are connected to oil recovery.The results show that the cycle-dependent relative permeabilities increase the potential for WAG. Furthermore, the oil production trends with respect to slug length and wateroil ratio is different for models with cycle-dependent hysteresis and without hysteresis.

show abstract

Immiscible WAG Injection in the Fensfjord Formation of the Brage Oil Field

Cited by 9 publications

References 0 publications

Progress in Immiscible WAG Modelling

Progress in Immiscible WAG Modelling

Gas Segregation During WAG Injection and the Importance of Parameter Scaling in Three-Phase Models

Simulation of the Immiscible WAG Process Using Cycle-Dependent Three-Phase Relative Permeabilities

Contact Info

Product

Resources

About