Fracturing with ihlight Weight ihproppants RPSEA Sub contract Number: 07122 38 Ming Gu Abhishek Gaurav Kishore Mohanty University of Texas at Austin 1
Outline Technical issues with fracturing shale gas Project objective Results Conclusions Future Directions
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
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
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
Ultra Light Weight Proppants (ULW) ULW1 (Polymeric) ULW2 (Resin impregnated Walnut hull) ULW3 (Resin coated Ceramic) Density 1.08 Sphericity 1 1.25 0.62±0.07 (Supplied by BJ Services) 1.75 0.78±0.01 Reference: White Sand
Size Distribution Percent 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Size Distribution 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 Sieve Size in inches ULW1 is broadest; ULW2 is largest; ULW3 is narrowest. ULW 1 14-40 ULW 2 14-30 20-35 ULW 3 courtesy: BJ Services 7
Results Strength Fracture conductivity Foam stability Proppant settling Foam rheology
Strength Test 9
SPE 138319 Light weight proppants Crush Test ULW 2 Pack Young s Modulus= 20000 psi 95 o C 10 Abhishek Gaurav
SPE 138319 Light weight proppants Crush Test Young s Young s % by avg wt % by avg wt modulus(psi) modulus(psi) fines formed fines formed @25 o C @95 o C @25 o C @95 o C ULW 1 25000 20000 4 0.4 ULW 2 25000 20000 2.5 1.5 ULW 3 45000 45000 14 30 11 Abhishek Gaurav
Fracture Conductivity Test 12
API Conductivity @ 95 C 1000 ULW 2 100 t Cond ductivity in md-ft 10 1 0.07 lbm/ft2 0.1 lbm/ft2 0.4 lbm/ft2 0.7 lbm/ft2 1 lbm/ft2 0.1 0 1000 2000 3000 4000 5000 6000 7000 Stress in psi Fracture conductivity decreases with overburden stress, about 1 md ft at 6000 psi 13
SPE 138319 Light weight proppants API Conductivity @ 95 C ULW-1 md-ft uctivity in Cond 10000 1000 100 10 1 0.1 0.01 0.1 1 Proppant Concentration in lbm/ft2 1000 psi 2000 psi 4000 psi 6000 psi 14 Sub-monolayer conductivity it is comparable to multilayer conductivity Abhishek Gaurav
SPE 138319 Light weight proppants API Conductivity @ 95 C ULW-2 Conduc ctivity in md-ft 10000 1000 100 10 1 0.1 001 0.01 01 0.1 1 Proppant Concentration in lbm/ft2 1000 psi 2000 psi 4000 psi 6000 psi 15 Sub-monolayer conductivity is comparable to multilayer conductivity Abhishek Gaurav
SPE 138319 Light weight proppants API Conductivity @ 95 C ULW-3 Conduc ctivity in md D-ft 10000 1000 100 10 1 001 0.01 01 0.1 1 Proppant Concentration in lbm/ft2 1000 psi 2000 psi 4000 psi 6000 psi 16 Conductivity increases with proppant concentration Abhishek Gaurav
How Much Conductivity is Needed? (McGuire & Sikora, 1960) Relative conductivity = (1 md ft/10 f/ 5 5 md)*1 = 10 5 1 md ft is high enough for shales 17
How Much Conductivity is Needed? (Agarwal et al., 1979) F f/( 5 f) CD = 1 md ft/(10 5 md x1000 ft) = 10 2 1 md ft is high enough for shales 18
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.
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
Foam Stability 120 4 100 3.5 (ml) Foam volume 80 60 40 3 2.5 2 15 1.5 wat ter volume (m ml) Foam Column length fluid level 150min 1 20 0.5 0 0 50 100 150 200 250 minute 0 Foam half-life ~ 150 min
Proppant Settling Velocity (V s ) Settling Vel locity (cm/ /s) 16 14 12 10 8 6 4 2 0 Water Sand ULW3 ULW2 Foam x x x x 1 ULW1 1.5 2 2.5 Nominal Density (gm/ml) V s = [0.072g( p w )] 0.71 d 1.14 / w 0.29 0.43 for water s [ g( p w )] / w V s = 0 for all the proppants and the sand in foam
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
Foam Rheology 2 1.5 log(d dp*d/4l) 1 0.5 0 0.5 1 1 1.5 2 2.5 3 3.5 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
Foam Rheology 3.00E+03 Cs=0.5wt% Q=30% Q=52% Q=59% Q=66% Q=72% 2.50E+03 2.00E+03 Re f 1.50E+03 1.00E+03 5.00E+02 0.00E+00 0 500 1000 1500 2000 γ w_ap (1/s) Flow of foam is laminar
Foam Rheology: Shear Rate & Quality Cs=0.5wt% 70 Q=52% Q=59% Q=66% Q=72% 60 Viscosity (cp) 50 40 30 20 10 0 0 200 400 600 800 1000 1200 1400 1600 1800 Shear Rate (1/s) Foam is shear thinning As quality increases, viscosity it increases Viscosity is about 20 40 cp
Foam Rheology: Effect of Composition p) Viscosity (c 80 70 60 50 40 30 20 10 0 27~30C, 1000 psi, 200 /s Cs=0.5wt%, Cg=2wt% Cs=0.5wt%, Cg=0wt% Cs=0.1wt%, Cg=0wt% 0 0.2 0.4 0.6 0.8 1 Quality As the surfactant and stabilizer concentration increases, viscosity increases
Foam Rheology: Effect of Pressure Cs=0.5wt%, Cg=0wt% (Pa) Shear Stress 40 35 30 25 20 15 10 5 0 Q=60%, 100psi Q=59%, 1000 psi Q=66%, 100psi Q=66%, 1000psi 0 200 400 600 800 1000 1200 1400 1600 Shear Rate (1/s) As the back pressure increases, viscosity increases
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.
Future Work Dynamic proppant settling Design of field test Daneshy Consulting working with Devon & BJ Field test & evaluation Working with Devon & BJ
Acknowledgements RPSEA Mr. Bill Wheaton, Devon Dr. Q. Qu, BJ Services Dr. A. Daneshy, Daneshy Consulting
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
Results ULW 1 ULW 2 ULW 3 Nominal density 1.08 1.25 1.75 Density of Pack 0.6 0.8 1.2 (g/cc) (without closure stress) Porosity of Pack 44 % 36 % 31% (without closure stress) Sphericity 1 0.62±0.7 0.78±0.1 Riley Sphericity Ψ 05 R =(D i /D c ) 0.5 33
Foam Rheology Cs=0.5wt% Q=0% Q=30% Q=52% Q=59% Q=66% Q=72% 10 τ w (Pa) 1 0.1 1 10 100 1000 10000 γ w_ap (1/s) Flow of water is turbulent Flow of foam is laminar