Enhancement of productivity after reservoir stimulation of the hydro-thermal reservoir Gross Schönebeck with different fracturing concepts
Günter Zimmermann & Geothermics GroupGeoForschungsZentrum Potsdam
Operations overviewopen hole proppant frac
Jan/Feb 2002production test / logging4130-4190m (frac 1)4080-4118m (frac 2)production test / logging
open hole waterfrac
start Jan/Feb 20033874-4294m, borehole instabilityproduction test
cont. Nov/Dec 20034135-4309mproduction test / logging
Dec 2004injection test
drilling 2. well
hydraulic stimulation of sandstones (Feb 2002)
qi
pwhpat
Open Hole Packer
7“ Liner
3 ½“ Fracstring
9 5/8“ Casing
5“ Fracstring
p,T Memory Fracinterval5 7/8“
OH-Interval
3874 m
4294 m
2309 m
Sand Plug
Expansion Joints
dzdpRRf
dzdpslurry
concept:
• open-hole stimulation
• high-viscous fluid(HTU-Gel + citric acid)
• proppant
result:
• increase of productivity
• FOI = 2
• not sufficient for economics
Legarth et al., Geothermics, 2003
flowmeter-log after gel-proppant treatment
4294 m
3874 m
7“ Liner 32#
7“ Liner-Hanger
9 5/8“ Casing
2309 m
2350 m
5 7/8“ borehole
13 3/8“ Casing
18 5/8“ stand pipe
205,3 m
open hole waterfrac (Jan/Feb 2003)
Siltstone
Vulkanites
Sandstone
max.25 l/s
250 bar
well Groß Schönebeck / casing profile
flow back test march 2003
0
5
10
15
20
25
30
0 5000 10000 15000 20000 25000
time [sec]
flow
[l/s
]
0
20
40
60
80
100
120
140
160
180
head
pre
ssur
e [b
ar]
head pressure
flow
productivity indexPI = 3-4 m³/(h MPa)FOI = 4
FMI measurements after 1. waterfrac treatment
Holl et al. EAGE, 2004
dept
h[ m
]
4127
4128
waterfrac cont. (Nov/Dec 2003)
4309 m
4134 m
3820,6 m3874 m
5“ Liner 15#, N80
7“ Liner 32#5“ Liner Hanger(15#, mech.) + integr. packer
7“ treatm. packer(IDmin 56 mm)
7“ Liner-Hanger
5“x3 ½“ G105IF-drillpipe (TK34);3 slip joints, ID 57 mm
9 5/8“ Casing
2309 m
2350 m
5 7/8“ borehole
5“, 15#, N80 pre-perforated Liner (93 holes/m, Ø1,5cm
Cup-Packer, OD 140 mm
2331,8 m
2300,6 m
13 3/8“ Casing
18 5/8“ stand pipe
4305,7 m
205,3 m
max.80 l/s
500 bar
pre-perforatedliner
well Groß Schönebeck / casing profile
massive waterfrac treatment nov. 2003
fracture dimensions
50
40
30
20
10
00 10 20 30 40 50
199
160
120
80
40
0
0.80
0.64
0.48
0.32
0.16
00 10 20 30 40 50
120
96
72
48
24
0
Rate (l/s) Fracture Length (m)
Total Fracture Height (m)Average Width (cm)
time (h)
productivity development
0
1
2
3
4
5
6
7
8
PI [m
³/(h
MPa
)]
CLT Jan2001 CLT Feb2002 PT Aug2002 IT Jan2003 FB Feb2003 FB Dec2003167 m³12,3 hours13,5 m³/h
307 m³14 hours22,4 m³/h
580 m³37 days1 m³/h
720 m³8,3 days3,6 m³/h
250 m³5 hours50 m³/h
859 m³24 hours50 m³/h
gel-proppant treatment
1. waterfrac treatment
2. waterfrac treatment
volumetimeflow rate
FOI = 2
FOI = 4
FOI = 8
Injection experiment 2004/2005
aim: transmissibility and flow profile
Q = 2 l/sInjection time = 18 daysShut-in = 76 daysRemaining head pressure = 4.5 MPa
Flow back & temperature logQ = 2 l/s
Injection experiment 2004/2005
8.0 -
4.0 -
2.0 -
time [days]0 10 20 30 40 50 60 70 80 90
flow
rate
[l/s] 0.0 -
pres
sure
[MPa
]
6.0 -
Injection experiment 2004/2005
Transmissibility T = k h = 4.1 x 10-14 m³ = 0.041 Dm
Fracture half length xf = 255 m
Fracture conductivity Fc = 9.6 x 10-13 m³ = 0.96 Dm
temperature logs during flow back 2005
4130
4140
4150
4160
4170
4180
4190
4200
4210
4220
4230
4240
4250
4260
138
139
140
141
142
143
144
145
146
147
temperature [°C]
dept
h [m
]
stat down stat up dyn down dyn up
dynamic temperture log
static temperature log
Flowrate q = 2 l/s
results & conclusion
- gel & proppant treatment in sandstones => FOI = 2problem: ⇒ generation of tensile fractures ⇒ no self propping effect⇒ number of proppant layers to low ⇒ closure of fractures at low differential pressure
- 1. massive waterfrac treatment => FOI = 4- 2. massive waterfrac treatment => FOI = 8problem: ⇒ only impact in volcanic rocks⇒ closure of sandstone layers at low differential pressure
recommendation: - separate treatments for sediments & volcanic rocks- waterfrac treatment in volcanic rock (with optional tie-back)- gel & proppant treatment in sediments
(with increasing number of proppant layers)
Quo vadis Groß Schönebeck 4?
Thermal-hydraulic modelling
Injection temperature T = 70°CReservoir temperature T = 150 °CQ = 75 m³/hSimulation time = 30 yearsFrac conductivity = 1DmTransmissibility = 1DmFrac half length GrSk3/90 = 150 mFrac half lengths GrSk4/05 = 250 m
GrSk3/90GrSk4/05
Injection experiment 2004/2005
Injection experiment 2004/2005
Transmissibility T = k h = 4.1 x 10-14 m³ = 0.041 Dm
Fracture half length xf = 309 m
Fracture conductivity Fc = 7.8 x 10-13 m³ = 0.78 Dm
Reservoir conditions (applied in FracPro)
10 mD0.145 bar/m59.3 MPaupperDethlingen
10 mD0.125 bar/m52.2 MPalowerDethlingen
1 mD0.16 bar/m68.4 MPavolcanics
pore fluidpermeability
closurestress gradient
fracpressure
Reservoir conditions (applied in FracPro)
0.59 MPa m1/20.1855 GPaupperDethlingen
0.59 MPa m1/20.1855 GPalowerDethlingen
1.72 MPa m1/20.255 GPavolcanics
fracturetoughness
Poisson‘sratio
Youngs modulus
productivity development
2-3103-5upperDethlingen
3-5306-10lowerDethlingen
3-5102-4Volcanics
FOI =PI(stim)/PI(initial)
productivity indexafter stimulation[m³/h MPa]
initial productivityindex[m³/h MPa]
waterfrac stimulation in volcanics
waterfrac stimulation in volcanics
Time (min)0 1600 3200 4800 6400 8000
00
160240
320480
480720
640960
8001200
0
40
80
120
160
200
Surface Pressure (bar) (698.93)BHP from Frac Model (bar) (968.68)
Total Friction (bar) (155.30)
Time (min)0 1600 3200 4800 6400 8000
0
2
4
6
8
10
0
5000
10000
15000
20000
25000Slurry Rate (m3/min) (9.00) Slurry Total (m3) (19776.83)
waterfrac stimulation in volcanics
Time (min)0 1600 3200 4800 6400 8000
00
400.40
800.80
1201.20
1601.60
1992
0
30
60
90
120
150
Fracture Length (m) (184.68)Average Width (cm) (1.73)
Total Fracture Height (m) (127.89)
Time (min)0 1600 3200 4800 6400 8000
0
24
48
72
96
120
0
6
12
18
24
30Fracture Upper Height (m) (101.53) Fracture Lower Height (m) (26.35)
Time (min)0 30 60 90 120 150
00
200100
400200
600300
800400
1000500
00
12016
24032
36048
48064
60080
BHP from WB Model and/or Data (bar) Model Net Pressure (bar) (153.42)
Surface Pressure (bar) (274.50)Total Friction (bar) (10.09)
Time (min)0 30 60 90 120 150
000
300000.80100
600001.60200
900002.40300
1.2e+053.20400
1.5e+054
500
00
3004
6008
90012
120016
150020
Proppant Total (kg) (118012.44)Slurry Rate (m3/min) (3.00)Slurry Total (m3) (421.63)
Proppant Concentration (g/L) (0.00)Proppant conc. in fracture (kg/m2) (18
gel-proppant treatment in sandstones
(kg/m2)(18,38)
gel-proppant fracture dimensions
Time (min)0 30 60 90 120 150
00
120.40
240.80
361.20
481.60
602
0
20
40
60
80
99
Fracture Length (m) (49.97)Average Width (cm) (1.24)
Total Fracture Height (m) (82.61)
Time (min)0 30 60 90 120 150
0
10
20
30
40
50.00
0
10
20
30
40
50.00
Fracture Upper Height (m) (43.22) Fracture Lower Height (m) (39.39)
proppant concentration
proppant concentration
Proppants
Expectations:
High conductive fracture, CfD ≥ 1
High long term permeability
Controlling movement of fines
Good placing of appropriate concentration
CarboHSP 20/40
83 % Al2O3, 5 % SiO2
ρ= 2.0 g/cm3
Crushtest 0.7 % fines at 67 MPa
