RPSEA Sub contract Number: Abhishek Gaurav. University of Texas at Austin

Transcription

1 Fracturing with ihlight Weight ihproppants RPSEA Sub contract Number: Ming Gu Abhishek Gaurav Kishore Mohanty University of Texas at Austin 1

2 Outline Technical issues with fracturing shale gas Project objective Results Conclusions Future Directions

3 Key Issues with Shale Gas Production Low connectivity between pore space and well bore: Multi stage hydraulic fracturing Need long fractures; proppant settling Water needed for fracturing fluid Water disposal (Cheasapeake Energy) 3

4 Key Issues with Shale Gas Production Low connectivity between pore space and well bore: Multi stage hydraulic fracturing Need long fractures; proppant settling Water needed for fracturing fluid Water disposal (Gadde et al., SPE 89875, 2004 ) 4

5 Project Objectives To develop non damaging fracturefluids fluids for long fractures in gas shale reservoirs Minimize water use Demonstrate their use by field tests Strategy: Ultra-light-weight proppants & foam 5

6 Ultra Light Weight Proppants (ULW) ULW1 (Polymeric) ULW2 (Resin impregnated Walnut hull) ULW3 (Resin coated Ceramic) Density 1.08 Sphericity ±0.07 (Supplied by BJ Services) ±0.01 Reference: White Sand

7 Size Distribution Percent 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Size Distribution Sieve Size in inches ULW1 is broadest; ULW2 is largest; ULW3 is narrowest. ULW ULW ULW 3 courtesy: BJ Services 7

8 Results Strength Fracture conductivity Foam stability Proppant settling Foam rheology

9 Strength Test 9

10 SPE Light weight proppants Crush Test ULW 2 Pack Young s Modulus= psi 95 o C 10 Abhishek Gaurav

11 SPE Light weight proppants Crush Test Young s Young s % by avg wt % by avg wt modulus(psi) modulus(psi) fines formed fines o o o o C ULW ULW ULW Abhishek Gaurav

12 Fracture Conductivity Test 12

13 API 95 C 1000 ULW t Cond ductivity in md-ft lbm/ft2 0.1 lbm/ft2 0.4 lbm/ft2 0.7 lbm/ft2 1 lbm/ft Stress in psi Fracture conductivity decreases with overburden stress, about 1 md ft at 6000 psi 13

14 SPE Light weight proppants API 95 C ULW-1 md-ft uctivity in Cond Proppant Concentration in lbm/ft psi 2000 psi 4000 psi 6000 psi 14 Sub-monolayer conductivity it is comparable to multilayer conductivity Abhishek Gaurav

15 SPE Light weight proppants API 95 C ULW-2 Conduc ctivity in md-ft Proppant Concentration in lbm/ft psi 2000 psi 4000 psi 6000 psi 15 Sub-monolayer conductivity is comparable to multilayer conductivity Abhishek Gaurav

16 SPE Light weight proppants API 95 C ULW-3 Conduc ctivity in md D-ft Proppant Concentration in lbm/ft psi 2000 psi 4000 psi 6000 psi 16 Conductivity increases with proppant concentration Abhishek Gaurav

17 How Much Conductivity is Needed? (McGuire & Sikora, 1960) Relative conductivity = (1 md ft/10 f/ 5 5 md)*1 = md ft is high enough for shales 17

18 How Much Conductivity is Needed? (Agarwal et al., 1979) F f/( 5 f) CD = 1 md ft/(10 5 md x1000 ft) = md ft is high enough for shales 18

19 Foam Fracturing Fluid 1. Less water consumption 2. Gas expanding after the treatment to help recovery of the liquid phase 3. The two-phase structure has high viscosity 4. Gel filtercake deposited on the formation face is thinner (control the fluid loss) 5 Littl t i d d if th fl b k 5. Little proppant is produced if the flowback rate is kept low.

20 Experimental Setup for Stability Test Bubble size:1mm (low flow rate ) Needle size inlet through the tape Bubble size:2 mm (high flow rate ) Schematic figure of the setup The bubble picture

21 Foam Stability (ml) Foam volume wat ter volume (m ml) Foam Column length fluid level 150min minute 0 Foam half-life ~ 150 min

22 Proppant Settling Velocity (V s ) Settling Vel locity (cm/ /s) Water Sand ULW3 ULW2 Foam x x x x 1 ULW Nominal Density (gm/ml) V s = [0.072g( p w )] 0.71 d 1.14 / w for water s [ g( p w )] / w V s = 0 for all the proppants and the sand in foam

23 Foam Rheology Flow Loop Gas cylin der Pressure Regulator Liquid Gear Pump Valves Mass Flow Meter Pressure Transducer BPR T P P T Disposal Liquid View Cell Heating Jacket (1 inch, 4ft) Pressure tested up to 2000 psi

24 Foam Rheology log(d dp*d/4l) log(8v/d) Q=0 Q=0.3 Q=0.52 Q=0.72 Flow of water is turbulent Flow of foam is not turbulent

25 Foam Rheology 3.00E+03 Cs=0.5wt% Q=30% Q=52% Q=59% Q=66% Q=72% 2.50E E+03 Re f 1.50E E E E γ w_ap (1/s) Flow of foam is laminar

26 Foam Rheology: Shear Rate & Quality Cs=0.5wt% 70 Q=52% Q=59% Q=66% Q=72% 60 Viscosity (cp) Shear Rate (1/s) Foam is shear thinning As quality increases, viscosity it increases Viscosity is about cp

27 Foam Rheology: Effect of Composition p) Viscosity (c ~30C, 1000 psi, 200 /s Cs=0.5wt%, Cg=2wt% Cs=0.5wt%, Cg=0wt% Cs=0.1wt%, Cg=0wt% Quality As the surfactant and stabilizer concentration increases, viscosity increases

28 Foam Rheology: Effect of Pressure Cs=0.5wt%, Cg=0wt% (Pa) Shear Stress Q=60%, 100psi Q=59%, 1000 psi Q=66%, 100psi Q=66%, 1000psi Shear Rate (1/s) As the back pressure increases, viscosity increases

29 Conclusions ULW proppant packs can endure stresses expected in Barnett shale (~4000 psi). ULW1 and ULW2 produce small amount of fines. Fracture conductivity is about 10 md ft at 4000 psi; large enough for shale stimulation. Fracture conductivity of sub monolayer is comparable to multilayer. Foams can be formulated that are stable during the fracturing process. The settling velocity increases with proppant density in water; settling is negligible gg in foams in static tests. Foam viscosity increases with quality & pressure and decreases with the shear rate.

30 Future Work Dynamic proppant settling Design of field test Daneshy Consulting working with Devon & BJ Field test & evaluation Working with Devon & BJ

31 Acknowledgements RPSEA Mr. Bill Wheaton, Devon Dr. Q. Qu, BJ Services Dr. A. Daneshy, Daneshy Consulting

32 Tasks Proppant properties 5/09 4/10 Foam formulation 5/09 4/10 Flow capacity 5/10 4/11 Proppant transport 5/10 4/11 Fracture design 5/11 10/1110/11 Field test & evaluation 5/11 4/12 32

33 Results ULW 1 ULW 2 ULW 3 Nominal density Density of Pack (g/cc) (without closure stress) Porosity of Pack 44 % 36 % 31% (without closure stress) Sphericity ± ±0.1 Riley Sphericity Ψ 05 R =(D i /D c )

34 Foam Rheology Cs=0.5wt% Q=0% Q=30% Q=52% Q=59% Q=66% Q=72% 10 τ w (Pa) γ w_ap (1/s) Flow of water is turbulent Flow of foam is laminar