Water production from shale oil and gas wells

Bing Bai

8/12/2013

Outline

• Wastewater characteristics• Wastewater production

• Vertical wells• Horizontal wells

• Sources of variability in water production volumes

• Water production prediction tools

Wastewater characteristics

• Frac flowback water– Fracturing fluids (15% – 40% recovery)– Water flows back after fracturing within 7 – 10

days– TDS: 30,000 – 200,000 mg/L– Chemical additives

• Produced water– Formation water + fracturing fluids– Water flows through the whole life time of well– High TDS– Oil & Grease and NORM

Wastewater production

• Vertical oil and gas wells• Arps Equation (Exponential decline) Q=Ae-kt

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

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2σ confidence interval

Average

Year

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Wastewater production

• Horizontal oil and gas wells• Arps Equation (Hyperbolic decline)

1 18 35 52 69 86 1031201371541711882052222392562732903073243413580

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Time, days

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Produced water (>164 days)

Transition water (31-163 days)

Frac Flowback (<30 days)

Wastewater production

• Horizontal well water production• Frac flowback water (30 – 35%)• Transition water (17 – 20%)• Produced water (53 – 55%)

10 15 20 25 30

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Produced water

Transition water

Frac flowback water

Year

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Water recovery ratio

• Frac flowback water: 21.75%• Transition water: 12.23%• Produced water: 28.26%(10 years) to 37.93% (30 years)

• Total water recovery ratio: 62.24% (10 years) to 71.91% (30 years)

DJ basin water production prediction

• Production per horizontal well• Flowback water: 13442.3 bbls (2137.2 m3)• Transition water: 8286.1 bbls (1317.4 m3)• Produced water: 10 year — 18766 bbls (2983.6 m3)

30 year — 26356.6 bbls (4190.4 m3)

• DJ basin water production prediction• Assume 1500 new horizontal wells are drilled each

year in DJ basin

• Water production volumes (DJ basin)• 30 day flowback: 20 million bbls (3.17 million m3)• 133 day transition: 12.4 million bbls (1.97 million m3)• Produced water: 10 year — 28.1 million bbls (4.47 million m3) 30 year — 39.5 million bbls (6.3 million m3)

• Total water produced from 1500 new horizontal wells in DJ basin

60.5 million bbls (10 year) — 71.9 million bbls (30 year) (9.61 million m3) (11.44 million m3)

DJ basin water production prediction

Sources of variability in water production volumes

Sources of variability in water production

• Temporal variability (decline curves)

1 19 37 55 73 91 1091271451631811992172352532712893073253433610

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Time, days

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Produced water (>164 days)

Transition water (31-163 days)

Frac Flowback (<30 days)

Frac floback Transition water Produced water

• Spatial variability (well location)• Formation, temperature, pressure, porosity

164179194209224239254269284299314329344359

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40Produced water

Field AField B

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31 41 51 61 71 81 91 101 111121 131141 151161

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1 4 7 10 13 16 19 22 25 28

0

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Sources of variability in water production

Time periodArea A(bbl)

Area B(bbl)

Two tail t-test(p value)

Frac flowback 14069.96 12279.41 0.03

Transiton water 8286.1 8290.74 0.94

Produced water 4496.6 4517.34 0.98

Total 26852.66 25087.49 0.54

• Wellbore length (frac stages)

Long: 38 stages (9500 ft/2900 m)Normal: 20 stages (5000 ft/1500 m)

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Sources of variability in water production

Time periodWater production

(bbl)

Water production volume per stage(bbl/stage)

Two tail t-test(p value)

  Long Normal Long Normal  

Frac flowback 26130 13420 690 670 0.71

Transition water 14750 8340 390 420 0.66

Produced water 6520 3540 170 180 0.52

Total 47400 25300 1250 1260 0.51

Sources of variability in water production

• Type of frac fluid

Type I — Guar based fluid with basic pH

Type II —Non-guar based fluid with low pH

1 10 19 28 37 46 55 64 73 82 91 1001091181271361451541630

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Type I

Type II

Time, days

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Sources of variability in water production

Time period Type I Type IITwo tail t-test

(p value)

Frac flowback 8802.49 7954.57 0.44

Transition water 5408.55 3442.38 0.046

Total 14211.04 11396.95 0.04

• Frac water source

Recycled: Recycled produced water (recycle ratio 1/7)

Non-recycled: Fresh water

Sources of variability in water production

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 860

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Recycled

Non-recycled

Time,days

Wat

er p

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Time periodRecycled/Fresh Blend (1/7)

(bbl)Fresh Water

(bbl)Two tail t-test

(p value)

Frac flowback 7620.32 8281.41 0.63

Transiton water 1783 1984.87 0.52

Water production prediction tools

Water production prediction tool

• Excel based tool

• ArcMap based tool

Water production prediction tool

Thank you!

Questions?