Improving Field Recovery, Sweep Efficiency through Optimizing Gas Injection / Gas Production in a Complex Mature Field

Naguib, M.; Hamdy, Ahmed; Hussein, Ahmed

doi:10.2118/77921-ms

Cited by 4 publications

(3 citation statements)

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“…A strategy was designed based on reservoir understanding as well as surface facilities and flowlines optimization considerations, as documented for other mature fields under similar challenges [6][7][8][9] .…”

Section: Field Backgroundmentioning

confidence: 99%

Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study

Soto¹,

Penuela²,

Benavides³

et al. 2006

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractCusiana is a field of three stacked reservoirs (Mirador, Barco and Guadalupe) of volatile oil with a rich gas cap at the top. After a decade of gas re-injection at the crest of the main reservoir, Mirador, the fluid composition has changed as a result of production/injection. The static framework of this highly heterogeneous reservoir has changed too. For instance, minor faults that were proved to be seals at initial conditions are leaking and fractures that used to be passive have been reactivated today.Initial miscible gas injection strategy in Mirador delivered so far an oil recovery factor (RF) of 50% with remaining oil in areas difficult to access such as an oil rim between the producers and a weak aquifer, poor quality rock layers, and bypassed between the producers and the gas injectors. In Barco and Guadalupe, initial water injection successfully provided pressure support but did not sweep oil as expected (RF= 25%).A strategy was designed to recover additional oil by moving gas injection points to deeper formations, the flank of the structure, injecting at low flow rates from distributed injection points and maintaining a favorable voidage replacement. This strategy was based on a synergy among the three reservoirs, which allowed well conversions, rehabilitation of 9 shut-in wells to be injectors or producers and conversion of 10.5 km of water injection flowline, which expanded the gas injection network.After 40% of the strategy implementation by the end of 2005, 1.8 MMSTB of incremental oil has been recovered, reducing the monthly field oil rate decline by half. This success has "boosted" the continuation of the gas injection redistribution strategy for 2006. This paper describes the geological and reservoir engineering modeling that was performed to design the gas injection redistribution strategy in this mature field.

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Section: Field Backgroundmentioning

confidence: 99%

Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study

Soto¹,

Penuela²,

Benavides³

et al. 2006

Proceedings of SPE Annual Technical Conference and Exhibition

View full text Add to dashboard Cite

show abstract

“…However, in a number of fields, it was noticed that in addition to the overlying sandstones or carbonates, the basement also contains oil and can be produced (Falt et al 1992;Naguib et al 2002;Harding et al 2002;Mack et al 2006). More recently, fractured basement reservoirs have been identified as the primary target for hydrocarbon production [e.g., Hazlett et al (2000); Shaosheng et al (2003); Ngoc et al (2007); Tezuka et al (2008)].…”

Section: Introductionmentioning

confidence: 99%

Predicting Effective Permeability to Oil in Sandstone and Carbonate Reservoirs From Well-Logging Data

Legrand

Kok²,

Neff

et al. 2011

SPE Reservoir Evaluation &Amp; Engineering

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The fractured basement field in Yemen described in this paper is characterized by two types of fracturing: background fractures with a very low effective permeability of less than 0.001 md and fracture corridors with an effective permeability of up to several millidarcies. Except for some dissolution porosity related to fracture corridors, no significant matrix porosity is encountered (total porosity is only 1.15%). Approximately one-half of the oil in place is contained in the fracture corridors and one-half in the background fractures.Production from this field commenced in 2007. It is currently produced by depletion. Compositional grading has been observed in the 3,120-ft oil column. Despite the fact that the oil is close to bubblepoint pressure at the top of the reservoir, a moderate increase in gas/oil ratio (GOR) has been seen.Detailed studies using material balance and discrete-fracturenetwork (DFN) models revealed that the reason for the slow increase in GOR is the low permeability of the background fractures. The low permeability leads to viscous forces being dominant over gravity forces and, hence, limited gravity segregation of gas and oil.Because of the relatively small viscosity difference between the gas and the oil in this field ( o / g = 6.5), the gas mobility is not much higher than the oil mobility at low gas saturations. Hence, oil and gas are produced effectively from the background fractures into the fracture corridors and the reservoir pressure is not depleting as fast as in reservoirs with higher viscosity difference between gas and oil. This results in a more effective solution-gasdrive recovery mechanism than that expected for a conventional reservoir.A number of reservoir-management strategies have been investigated. The results indicate that the low permeability of the fracture corridors and very low permeability of the background fractures lead to low recovery factors of 14% for gas injection. However, the efficiency of solution-gas drive is higher than in conventional reservoirs.

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“…However, in a number of fields, it was noticed that in addition to the overlying sandstones or carbonates, the basement contains oil as well and can be produced (Falt et al 1992, Naguib et al 2002, Harding et al 2002, Mack et al 2006). More recently, fractured basement reservoirs have been identified as the primary target for hydrocarbon production (e.g Hazlett et al 2000., Shaosheng tel al.…”

Section: Introductionmentioning

confidence: 99%

Recovery Mechanisms and Oil Recovery From a Tight, Fractured Basement Reservoir, Yemen

Legrand

Kok

Neff

et al. 2010

SPE Annual Technical Conference and Exhibition

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The fractured basement field in Yemen described in this paper is characterised by two types of fracturing: background fractures with a very low effective permeability of less than 0.001 mD and fracture corridors with an effective permeability of up to 1 mD. Except for some dissolution porosity related to fracture corridors, no significant matrix porosity is encountered (total porosity is 1.15 % only). About half of the oil in place is contained in the fracture corridors and half in the background fractures.Production from this field commenced in 2006. It is currently produced by depletion. Compositional grading has been observed in the 3120 ft oil column. Despite the fact that the oil is at bubblepoint pressure at the top of the reservoir, a moderate increase in gas/oil ratio (GOR) has been seen.Detailed simulation studies revealed that the reason for the slow increase in GOR is the low permeability of the background fractures. The low permeability leads to viscous forces being dominant over gravity forces and hence almost no gravity segregation of gas and oil.Due to the relatively small viscosity difference of the gas and the oil in this field, the gas mobility is not much higher than the oil mobility at low gas saturations. Hence, oil and gas are produced effectively from the background fractures into the fracture corridors and the reservoir pressure is not depleting as fast as in reservoirs with higher viscosity difference of gas and oil.A number of reservoir management strategies have been investigated. The results indicate that the low permeability of the fracture corridors and very low permeability of the background fractures results in challenging conditions for increasing oil recovery by water or gas injection. However, the efficiency of depletion drive is higher than in conventional reservoirs.

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Improving Field Recovery, Sweep Efficiency through Optimizing Gas Injection / Gas Production in a Complex Mature Field

Cited by 4 publications

References 0 publications

Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study

Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study

Predicting Effective Permeability to Oil in Sandstone and Carbonate Reservoirs From Well-Logging Data

Recovery Mechanisms and Oil Recovery From a Tight, Fractured Basement Reservoir, Yemen

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