Long Term Cement Integrity Long Term Cement Integrity for Tight Gas Wellsfor Tight Gas Wells
in Hungaryin Hungary
11
in Hungaryin Hungary
Roeland Verbakel,Roeland Verbakel,Geomarket Technical Engineer, Geomarket Technical Engineer,
Schlumberger Well IntegritySchlumberger Well Integrity
OutlineOutline
� Introduction to Tight Gas Wells
� Cementing Challenges and Solutions
22
� Case history
� Summary
Introduction Introduction –– Tight Gas Tight Gas ChallengesChallenges
� Tight Gas Environment� Reservoir Pressure >
10,000 psi (69 MPa)
� Static Temp > 170°C
� Depths from 3500 to 6000m
33
6000m
� Commercial production not possible without hydraulic fracturing (tight gas)
� Unique challenges for cementing� Changes in pressure and temperature
� High temperature and pressure
Tight Gas well is a stressful Tight Gas well is a stressful environmentenvironment
Temperature changes in upper
casings during production
44
Pressure changes: drilling, production
Hydraulic stimulation
Well completion/perforation
Stress AnalysisStress Analysis
� Need to be able to analyze the stresses in the wellbore� Young’s modulus� Rock, cement and casing
Compressive strength
55
� Compressive strength� Tensile strength
� Young’s modulus, CS, Poisson's Ratio and thermal expansion play a complex role in durability
Gas MigrationGas Migration
� Formation
� Mud Removal
� Slurry Properties− Density
− Fluid Loss
− Free Water
Static Gel Strength development
66
− Static Gel Strength development
− Porosity
− Shrinkage
− Permeability to gas
High Pressure,High Pressure,High Temperature EnvironmentHigh Temperature Environment
� High density slurry using multi-modal blend design
� High Solid Volume Fraction
� Very low permeability
� Prevent gas migration
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� Good mixability
� Quality control at each stage of design and execution
Cementing Challenges and Cementing Challenges and SolutionsSolutionsEngineering approachEngineering approach
Tight gas well
SolutionCementing
Challenge
Fracturing
TreatmentStress Analysis
Flexible
Slurry
Analysis
Tool
�Flexible Slurry
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Treatment
Short term
gas migration
Micro-annulus
High
Mud Weight
Gas Migration
Analysis
Stress Analysis
Hydraulic
Simulations
Gas migration
additives
Expanding
Agent
High density
Slurry
�High Density
Slurry
Case history Case history –– Tight Gas well in Tight Gas well in Pannonian BasinPannonian Basin
� 500 meter x 4 ½’’ Liner in 5 7/8’’ OH
� Gas pressure of formation 10 kpsi (69 Mpa)
0
m
99
(69 Mpa)
� Reservoir temperature 175°C
2000
4000
Well
Hydraulic simulations and fluid Hydraulic simulations and fluid rheologyrheology
2500
.030
00.0
m
0 20 40 60 80 100Time (min)
32
10W
HP
(ps
i) (
x 10
00) Calc. WHP
Calc. Pump Press.
4F
low
Rat
e (b
bl/m
in) Q In
Fluids at 3749 m
600
500
400
300
She
ar S
tres
s (lb
f/100
ft2)
Mud (Model : HERSCHEL_B., Temp : 50 degC, Pres : undefined)DensCRETE (Model : HERSCHEL_B., Temp : 85 degC, Pres : undefined)MUDPUSH WHT (Model : HERSCHEL_B., Temp : 85 degC, Pres : undefined)
Shear Stress Vs Shear RateHierarchical Rheograms
1010
3500
.040
00.0
Fluid Sequence
0 20 40 60 80 100Time (min)
20
Flo
w R
ate
(bbl
/min
) Q InQ Out
0 20 40 60 80 100Time (min)
2118
1512A
nn. P
ress
ure
(lb/g
al)
FracPoreHydrostaticDynamic
Depth = 3749 m 0 0.1 0.2 0.3Shear Rate(1/s) (x 1000)
200
100
0S
hear
Str
ess
(lbf/1
00ft2
)
Results of the cementing Results of the cementing operationoperation
� Logs run 8 days after the cementing operation
� Exchange to completion fluid 6 days after the job (38 MPa difference)
� Log was affected by micro-annulus
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annulus
� Expanding agent was used in slurry to close micro-annulus over time
� During hydraulic fracturing treatment on the well (3 months later), cement showed good isolation
� No remedial work was needed
SummarySummary
1. Tight Gas cementing operations in Pannonian Basin are very challenging
2. Complete portfolio of design tools is utilized for complex cementing design
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cementing design
3. Slurry quality control and assurance (QA/QC) is key to success
4. Correct well construction first time: critical