scaling of hydraulic fracturing operations to lab ... saied mighani.pdf · 01 toughness viscosity...

Scaling of Hydraulic Fracturing Operations to Lab Experiments

Saied Mighani, Jianhua GongGraduate student, EAPS

Under supervision of Brian Evans

MIT Earth Resources Laboratory2017 Annual Founding Members MeetingJune 1st, 2017

2016 Annual Founding Members Meeting 2

Scaling Hydraulic Fracturing Operations Lab Experiments

Field operation HF

MIT Earth Resources Laboratory2017 Annual Founding Members Meeting

Slide 3

1400 m3!

Garcia et al., 2013

Governing equations for propagation of a fluid-filled fracture


Slide 4

𝐾" = 42𝜋

�𝐾 )*

1- Conservation of mass.

2- Elastic deformation 𝐾" =8𝜋

2𝑅

�-

𝑝 𝑟"

𝑅0 − 𝑟"0� 𝑑𝑟"

3

4

3- Fracture criterion

Detournay, 2016

R fracture length𝛔o min. (lith.) prin. stress E’ Plane strain modulus𝑅6 fluid-filled frac. length H sample lengthw frac. width KIC frac. toughnessQo fl. injection rate K’ stress Intensityp fl. net pressure 𝐾"7 Fluid leak-off constant𝛍 fl. viscosity

𝑄4𝑡 = 2𝜋- 𝑤𝑟" 𝑑𝑟"3<

4+ 𝜋-

𝐾"7𝑅60 𝑡"

𝑡 − 𝑡"� 𝑑𝑡" >

4

Dimensionless Time Constants


Slide 5

𝜓@ =�̅� C𝑞4

C𝐸"@C

𝐻C𝐾"04

@ 0⁄

𝜓0 =𝐾"C

𝜎4 C𝐻C 0⁄ 𝜓I =𝐾"@4𝑞4

@4

𝐾"704𝐻@C𝐸"@4

@ J⁄

Bunger et al., 2005; Detournay, 2016

𝛔o min. (lith.) prin. stress E’ Plane strain modulusqo fl. injection rate K’ modified mode I fracture toughnessH desired fracture length 𝐾"7 Fluid leak-off constant

Symbols, variables, and constants

viscosity Fluid lag Leak-off


Slide 6


𝜓I>>1 𝜓I<<1 (leakoff)𝜓@<<1 𝜓@>>1 𝜓@<<1 𝜓@>>1

𝜓0<<1 Toughness Viscosity Toughness Viscosity

𝜓0>>1 Toughness Viscosity and Fluid lag Toughness Viscosity and Fluid lag

Dimensionless Time Constants

𝜓@ =�̅� C𝑞4

C𝐸"@C

𝐻C𝐾"04

@ 0⁄

𝜓0 =𝐾"C

𝜎4 C𝐻C 0⁄ 𝜓I =𝐾"@4𝑞4

@4

𝐾"704𝐻@C𝐸"@4

@ J⁄

viscosity Fluid lag Leak-off


Slide 7

𝜓@ = 960 𝜓0 = 6 ×10P@4 𝜓I = 1.7×10J


Operations Parameters




Injection rate Fluid viscosity

Min. in-‐situstress

Tensile strength

Young’s modulus

Fracture toughness

Leakoff constant

10 m3/min 1 cp 40 MPa 15 MPa 40 GPa 1.8 MPa.m0.5 10-‐06 m.s-‐0.5


Slide 8Experiment Design

Fluid name: Silicone oil A B C DFluid Viscosity (P·s) 0.1 1 5 12.5

Injection rate (m3/sec) 3.6×10-06 4×10-8 7×10-9 3×10-9

Viscosity

Toughness

Fluid lag

No fluid lag


Slide 9ExperimentsExp. # Specimen 𝝈𝟑, 𝝈𝟏(M

Pa)Fluid Viscosity (cp) Injection rate

(ml/sec)𝝍𝟏 𝝍𝟐 𝝍𝟑

1 Solnhofen limestone

5/10 Argon 0.02 4.9 1 e-‐6 3.5 e4 9 e9

2 Solnhofen limestone

5/10 Silicone Oil

100 3.6 970 3.5 e4 9 e9

3 PMMA 5/10 Silicone Oil

100 3.6 2e-‐4 4 e4 3 e11




Tough

Vis & lag

Tough


Slide 10Experiment Configuration

Strain gauge

notch

Pressure transducer

Radial LVDT

Axial LVDT


Slide 11Experiment Configuration

Radial LVDT Axial LVDT

Pressure transducer


Slide 12Experiment3- PMMA (Toughness-dominated regime)Fluid: silicone oil 100 cp

Axial LVDT: Compression +Radial LVDT: Compression +



1 mv ~ 0.005 m/secSheibani, 2017

AE event for 2 msecs!

5.4 5.5 5.6 5.7 5.8 5.9

x 10-3

10

20

30

40

50

60

70

80

90

100

time, sec

Volta

ge, m

volts



Blue early red latePoint size corresponds to event magnitude (first motion)

We were able to locate 32 out of 50 events.



Amplitu

de, m

v

Dry borehole Sat. borehole After HF-‐frac open After HF-‐frac closed

Time, µsec

Amplitu

de, m

v

Sensor 11

Vp before HF: 2696 m/secVp after HF: 2287 m/sec (15% decrease = generated pathway for hydrocarbon flow)


Slide 16Experiment2- Solnhofen limestone (Viscosity-dominated regime)Fluid: silicone oil 100 cp



We could not detect any AE’s for experiment 2!

Testing a hypothesis:Is this because the rock specimen can not generate AE events or

the HF in viscosity-regime behaves differently?



Fracture propagation velocity: (500-‐200 m/s)Based on experimental parameters: the experiment was in

toughness-‐dominated regime

So, we could register AE events in Solnhofen limestone but in a different regime!

Gu, 2016


Slide 19Energy budget anlaysis

𝐸7 + ∆𝑊 = 𝐸[\ + 𝐸] + 𝑙 + 𝐸3

Energy budget analysis:

Goodfellow et al. (2015)

Injection system +Δ(Elastic potential)= Griffith release+ crack deformation + Losses+ seismic


Slide 20Energy budget analysis

0.3 Hz

∆𝑊 = 4.7585𝑒 − 04 J 𝐸3 = 3.3449𝑒 − 05 J

So, 99. 99 % of the input energy turns non-‐seismic!


Slide 21Summary

• Field operations were in the viscosity-‐dominated regime

• We can conduct experiments in different regimes by changing the pumping rate, fluid viscosity and confining stress.

• Toughness-‐dominated regime in PMMA and earlier Solnhofen tests:

AE occurrence over 2 ms interval and 15% reduction in velocity.Very rough estimate indicates 99. 99 % of the input energy is non-‐seismic

• No AE generated in viscosity-‐dominated regime in Solnhofen limestone

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