Flood Design for Oil Reservoirs - University of · PDF filePaul Willhite – University of...

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E

Flood Design for Oil Reservoirs

MINNELUSA WORKSHOP

MAY 6&7, 2013 GILLETTE, WYOMING

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Disclaimer and Acknowledgements All data and information contained within this presentation are from public sources. Furthermore, all analyses and interpretations have been conducted with publically available data. THIS MATERIAL WAS PREPARED AS AN ACCOUNT OF WORK PRODUCED BY AN AGENCY OF THE STATE OF WYOMING. NEITHER THE STATE OF WYOMING, NOR THE UNIVERSITY OF WYOMING, NOR THE ENHANCED OIL RECOVERY INSTITUTE (EORI), NOR ANY OF THEIR EMPLOYEES, MAKES ANY WARRANTY, EXPRESS OR IMPLIED, OR ASSUMES ANY LEGAL LIABILITY OR RESPONSIBILITY FOR THE ACCURACY, COMPLETENESS, OR USEFULNESS OF ANY INFORMATION, APPARATUS, PRODUCT, OR PROCESS DISCLOSED, OR REPRESENTS THAT ITS USE WOULD NOT INFRINGE PRIVATELY OWNED RIGHTS. THE EORI RESERVES THE RIGHT TO CHANGE, AMEND, ALTER, ADDEND OR REMOVE THE CONTENTS OF THIS MATERIAL IN FUTURE EDITIONS BOTH IN PART OR IN ITS ENTIRETY. THIS DISCLAIMER IS MADE WITH RESPECT TO THE DOCUMENT AS WELL AS THE ASSOCIATED DATA.

• The author kindly acknowledges the contributions of the following individuals: Aboozar Hesami, EORI Glen Murrell, EORI Shaochang Wo – EORI Paul Willhite – University of Kansas Larry Lake – University of Texas

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Fundamental Principles

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• Porosity • Permeability • Rock & fluid properties • Rock & fluid interactions General understanding of multi-phase flow in porous media

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Primary Production

• In the early days of oil production, saline water or brine was typically produced with oil.

• As primary production matured, brine production typically increased.

• Produced water in the early days was discharged by dumping it into streams and rivers.

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Waterflooding • Practice of water injection or waterflooding

began accidentally. • Bradford Field (PA) was an early attempt involving

systematic waterflooding. • Wells in the 1880s were abandoned in the

Bradford Field by pulling casing without plugging. • Systematic water injection in the Bradford Field

may have begun as early as 1890. • By 1907, the practice of water injection had an

appreciable impact of oil production in the Bradford Field.

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Waterflooding • Waterflooding expanded rapidly after the PA legislature

legalized water injection into oil bearing zones in 1921. • 5-spot flooding gradually replaced circular or

peripheral floods and line drive floods in the late 1920s.

• Water injection operations were reported in Oklahoma in 1931, Kansas in 1935, and Texas in 1936.

• By the 1970s, waterflooding was implemented in most onshore fields in the U.S., China, and Russia for waterflooding made technical sense.

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Mature Oil Fields

• In 2013, 70 percent of world oil production is produced from mature oil fields.

• Characteristics of mature fields – Fields have operated for more than 25 to 40 years, – Produced oil cuts are less than 3 percent, and – Equipment, both surface and subsurface, are at

the end of operating life.

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Diagram of a Water Drive Reservoir

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Darcy’s Law- Linear Flow

𝑸 = −𝑲𝑲𝝁

∗ (𝑷𝒃 − 𝑷𝒂)

𝑳

K: Absolute Permeability A: Cross-Sectional Area µ: Viscosity 𝑃𝑏 − 𝑃𝑎: Pressure Differential L: Length between 𝑃𝑏 & 𝑃𝑎

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Darcy’s Law- Radial Flow

𝒒 =𝑲𝑲(𝑷𝒆 − 𝑷𝒘𝒘)

𝟏𝟏𝟏.𝟐 ∗ 𝝁 ∗ 𝑩𝒐 ∗ 𝒍𝒍𝒓𝒆𝒓𝒘

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Darcy’s Law- Radial Flow Bottom Hole Pressure= 5,500 psia Reservoir Pressure= 6,000 psia Oil Viscosity- 0.25 cp Formation Volume Factor- 1.5 𝑏𝑏𝑏 𝑆𝑆𝑆⁄ Permeability= 20 md Thickness= 30 ft. Drainage Radius= 1,000 ft. Well Bore Radius= 0.5 ft.

𝒒 =𝟐𝟐 𝟑𝟐 𝟔,𝟐𝟐𝟐 − 𝟓,𝟓𝟐𝟐

𝟏𝟏𝟏.𝟐 𝟐.𝟐𝟓 𝟏.𝟓 𝒍𝒍 𝟏,𝟐𝟐𝟐𝟐.𝟓

𝒒 = 𝟕𝟏𝟓 𝒔𝒔 𝒃𝒃

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Pore-Scale Immiscible Displacement • The presence of immiscible fluids in reservoir

rocks alters the capacity of a rock to transmit fluids.

• Physical properties that affect fluid and rock interactions – Interfacial tension – Wettability – Capillary pressure

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Relative Permeability • Effective permeability data are generally presented as

relative permeability data. • The relative permeability is defined as the ratio of the

effective permeability of a phase to a base permeability. Three different base permeabilities are used including: – Absolute air permeability, – Absolute water permeability, and – Effective permeability to oil at residual wetting-phase

saturation. • It is necessary to know which base permeability was

used for a particular set of relative permeability data.

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Relative Permeability

“A rigorous proof that verifies the extension of Darcy’s law to multiphase flow in porous media has not been developed.” Dr. G. Paul Willhite, 1986

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Residual Oil

Flood-Out

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Residual Oil

Economic Limit

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Mobilization of Residual Oil Drainage

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Oil Displacement- Imbibition

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Continuity Equation

𝑀𝑀𝑀𝑀 𝑜𝑜 𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑜𝑒𝑒 𝑒𝑡𝑒 𝑑𝑜𝑜𝑜𝑒𝑒𝑒𝑒𝑒𝑜𝑀𝑜 𝑒𝑜𝑒𝑒𝑒𝑒𝑒 𝑜𝑒 𝑒𝑡𝑒 𝑒𝑜𝑒𝑒 𝑜𝑒𝑖𝑒𝑒𝑒𝑒𝑒𝑒 ∆𝑒

− 𝑀𝑀𝑀𝑀 𝑜𝑜 𝑜𝑜𝑜 𝑜𝑒𝑀𝑙𝑜𝑒𝑒 𝑒𝑡𝑒 𝑑𝑜𝑜𝑜𝑒𝑒𝑒𝑒𝑒𝑜𝑀𝑜𝑒𝑜𝑒𝑒𝑒𝑒𝑒 𝑜𝑒 𝑒𝑡𝑒 𝑒𝑜𝑒𝑒 𝑜𝑒𝑖𝑒𝑒𝑒𝑒𝑒𝑒 ∆𝑒

= 𝑀𝑀𝑀𝑀 𝑜𝑜 𝑜𝑜𝑜 𝑒𝑡𝑀𝑒 𝑀𝑖𝑖𝑎𝑒𝑎𝑜𝑀𝑒𝑒𝑀 𝑤𝑜𝑒𝑡𝑜𝑒

𝑒𝑡𝑒 𝑑𝑜𝑜𝑜𝑒𝑒𝑒𝑒𝑒𝑜𝑀𝑜 𝑒𝑜𝑒𝑒𝑒𝑒𝑒𝑜𝑒 𝑒𝑡𝑒 𝑒𝑜𝑒𝑒 𝑜𝑒𝑖𝑒𝑒𝑒𝑒𝑒𝑒 ∆𝑒

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Continuity Equation

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Continuity Equation

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Buckley- Leverett Solution

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Oil Saturation Distribution During a Waterflood

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Geological Considerations Waterflooding

1. Location and extent of porous and permeable (conductive) layers that contain residual oil.

2. Presence of impermeable layers that separate the porous and permeable zones in a reservoir.

3. Features in the conductive zones that may result in interbedding (smaller features that inhibit flow).

4. Directional permeability trends that are caused by the depositional environment or by diagenetic changes.

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Geological Considerations Waterflooding

5. Reservoir mineralogy. 6. Fracture trends that develop because of regional tectonic stresses on the reservoir rock. 7. Fault trends that affect the connection of one part of the oil reservoir to adjacent areas of the reservoir 8. Presence of a natural water drive. 9. Reservoir orientation/dip.

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Key Data Required to Evaluate the Reservoir

– Open hole logs – Core data – Cased hole logs – Original reservoir pressure – Reservoir pressure history – Water levels in producers – DST/original well test results – Well construction – Well histories – Field development history – Oil production rate and cumulative production by well – Water production rate and cumulative production by well – Water injection rates and pressures by well – Gas content in oil in the reservoir – API gravity – Oil viscosity – Water analyses

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Waterflood Design • Well patterns • Well spacing • Completion intervals • Completion techniques • Conversion of wells • Infill drilling • Water compatibility • Injection program • Water allocation

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Preferential Flow

• Vertical distribution – High permeability zones – Injection into multiple zones

• Horizontal distribution – Eolian sands – Orientation of sand dunes – Size of dunes

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Minnelusa Field Map Geological Model #1

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Minnelusa Field Map Geological Model #2

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Minnelusa Field Map Geological Model #3

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Cross Section A-A`

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Cross Section B-B`

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History – Field Development

Discovery 1970

2nd Well 1970

3rd Well 1970

4th Well 1970

5th Well 1970

6th Well 1984

7th Well 2003 Injection

3rd Well 1978 Injection

4th Well 1989 Injection

3rd well 1991 Abandon

1st Well 1994 Injection

6th well 2001 Abandon

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Oil Production and Water Injection Field History (end 2012)

• Total oil production: 1800000 STB • Total water production: 1300000 STB • Total gas production: 40000 MSCF • Total water Injection: ???? STB

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Production Well Evaluation Well #1

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Production Well Evaluation Well #2

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Production Well Evaluation Well #3

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Production Well Evaluation Well #4

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Production Well Evaluation Well #5

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Production Well Evaluation Well #6

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Injection Well Evaluation Offset Response #1

Clear Response

No Response

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Injection Well Evaluation Offset Response #2

Clear Response

Weak Response

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Injection Well Evaluation Offset Response #3

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Waterflood Monitoring • Injection profiles

– Flow (Spinner surveys) – Thermal

• Interference testing • Pressure buildup and falloff testing • Offset response • Tracer testing • Construction of new wells

– Open-hole logs – Measure residual oil from core samples – Pump testing during completion

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Summary • The geology of a reservoir affects the waterflood

design and performance. • Preferential flow in the most conductive zones

(thickest, most permeable) will affect waterflood efficiency.

• Typically, approximately 50 percent of the best part of a Minnelusa reservoir may be swept in a good waterflood.

• Waterflood conformance can be improved through infill drilling, recompletions, conversions, and work overs.

• Good waterfloods make good chemical floods.

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SPE References • Craig, F. G., The Reservoir Engineering Aspects of

Waterflooding, Society of Petroleum Engineers, Vol 3., Henry L. Doherty Series, 1970.

• Lake & Holstein, Petroleum Engineering Handbook, Volume V, Society of Petroleum Engineers, 2007.

• Towler, Brian F., Fundamental Principles of Reservoir Engineering, SPE Textbook Series Vol. 8, 2002.

• Willhite, G. Paul, Waterflooding, SPE Textbook Series Vol. 3, 1986.

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David Mohrbacher jmohrbac@uwyo.edu

307 760 3166

Questions?