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Fracture Design Basics - 101 (Fracturing is not for Dummies)

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Title: Fracture Design Basics - 101 (Fracturing is not for Dummies)


1
Fracture Design Basics - 101 (Fracturing is not
for Dummies)
  • Pat Handren Denbury Resources, Inc

2
Introduction
  • Basics of fracture design
  • A general knowledge of what to look for and why,
    and then what to do with it
  • Does anyone know anything about fracturing?

3
Agenda
  • The beginning perforating, logs
  • The basics of design fluid volumes, proppant
    volumes, scheduling
  • Rules of thumb (not to be mistaken for rules of
    dumb)
  • Measuring results

4
Why Fracture??
  • Drilling damage
  • Tight rock (sandstones, limestones)
  • Unconventional reservoir (shales)
  • Sand consolidation
  • Frac pack
  • Mostly accelerate production and increase
    reserves

5
Candidate selection criteria
  • Permeability, k
  • Porosity, f
  • Reservoir pressure
  • Lithology, mineralogy
  • Cost/economics
  • Wellbore mechanics
  • Others???

6
Vocabulary
  • Stress, s
  • Width, w
  • Height, h
  • Length, Lf and Lcreated
  • Concentration, ppg and /ft2
  • Efficiency (of fluid)
  • Screen out (well self-optimization)

7
Rock Stresses
  • Horizontal stresses
  • Squeeze the hole
  • Compression side
  • Tension side
  • Fracture created perpendicular to least principal
    stress

s min
s max
8
Perforating (Just touching the surface!)
1 shot/ft
9
Logs
  • Its dark down there
  • Look at everything on the log
  • Gamma ray
  • Resistivity
  • Porosity
  • Caliper
  • Rwa
  • Tension

10
Start with an easy one
  • Gamma ray, 30 API units
  • Resistivity, 8-9 ohm-m
  • Porosity, 18
  • Caliper, in gauge
  • Rwa, 0.5
  • Tension, log pulls
  • Frac height 110

11
It does get more difficult!
  • Limited entry how many perfs, how big an entry
    hole and where to put them
  • Casing size rate limitations
  • Cost treat separately or all at once?

12
Basics of Design
  • How tall?
  • Thats why we look at logs.
  • How Wide?
  • Pick a fluid type!
  • How long?
  • Tight means longer, gt 350
  • Permeable means shorter, lt 100

13
Rules of Thumb
  • Slick water 1-3height per bpm rate
  • Foams 2-4
  • Cross linked - 4-6
  • Slick water foam average width 0.2
  • Cross linked average width 0.4
  • Slick water average concentration 1-1.2 /ft2
  • Cross linked average conc 2 /ft2
  • Slick water max 3 /gal
  • Foam max???
  • Cross linked max 12 /gal
  • Propped length 0.7 X created length

14
Design a frac
  • Frac height 110
  • Crosslinked Fluid
  • Min Rate 110/4 or 6 20-28 bpm
  • Width 0.4
  • Tight rock 350 fracture half-length
  • Design on 2 /ft2

15
Frac Design in Action
Fracture volume Width Height Length
(1/Efficiency) 2
Frac volume .4/12 110 (350 /0.7) (1/.6)
2 6111 ft3 1090 bbls
Proppant volume 2 /ft2 110 350 2
154,000 pounds
Width 0.4 inches
Height 110 ft
Propped Length 350 ft
16
Frac Schedule for Fluid
  • Rule of 17 (probably wont find this in a book)
    for Fluid (works for cross linked or foam fluids
    rules are different for slick water fracs)
  • Pad 2 17 34
  • Stage 1 17
  • Stage 2 17
  • Stage 3 17
  • Stage 4 15 (thats all thats left)
  • For our 1090 barrel job
  • Pad 370.6 bbls 15565 gals 15,500 gals
  • Stage 1, 2 3 185.3 bbls 7783 gals 7800
    gals each
  • Stage 4 163.5 bbls 6867 gals 6800 gals

17
Proppant distribution
  • Stage 1 4 fluid volume 30,200 gallons
  • Stage 1 4 proppant volume 154,000
  • Average slurry concentration 5.1 /gal
  • Proppant schedule
  • Stage 1 7800 2 15,600
  • Stage 2 7800 4 31,200
  • Stage 3 7800 6 46,800
  • Stage 4 6800 8 54,400
  • Total prop in schedule 148,000
  • Add 750 gallons to 8 ppg stage to get to 154,000
    total

18
Another Rule of Thumb
  • 50 of proppant in last third of slurry
  • Total slurry stage 30,950 gals/3 10,317 gals
  • 7550 gals 8 ppg 60,400
  • 2767 gals 6 ppg 16,602
  • 77,002 / 154,000 50
  • Why?

19
Where is proppant most important
  • Deepest water leak-off is near wellbore
  • Flow rate increases toward wellbore
  • Decreases pressure drop along fracture

20
What happened?
  • Actual frac job designed for 450 bbls pad and
    872 bbls slurry with 158,000 16/20 proppant at
    36 bpm
  • Different than the design because of prior field
    knowledge and experience
  • Results SICP 5500 psi. FCP 4300 psi, 12/64
    chk, 3540 Mcf/d, 34 BC, 57 BW.

21
Summary
  • Basics of fracture design
  • Height, width and length
  • A general knowledge of what to look for and why,
    and then what to do with it
  • Logs, Rules of Thumb, Rule of 17
  • Does anyone know anything about fracturing?

22
Where to Get More Information
  • Training sessions - in-house or pay for course
  • Fracturing Monograph, Books
  • Read everything believe somethings
  • Find a mentor

23
  • QUESTIONS???
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