an excursion through water saturation methods from cased ... · an excursion through water...
TRANSCRIPT
Schlumberger-Private
An excursion through water saturation methods from
cased hole logging
Chiara Cavalleri
Principal Petrophysicist, Schlumberger
London, 13-Dec-2018
Schlumberger-Private2
▪ Introduction
▪ Formation evaluation behind casing
▪ Saturation methods and examples
▪ An integrated approach
▪ Summary
Outline
Schlumberger-Private
▪ Cased-hole formation evaluation has a primary role for the proper description of the existingreservoir systems; but also new players in particular conditions.
▪ Help finding that additional drop of oil
▪ Assisting completion design or intervention programs
▪ Characterization of new reserves managing costs and operational risks.
▪ Alternative saturation methods are available behind casing; with or without open hole logs
▪ Current technology is the enabler, even in tough logging conditions.
Introduction
Schlumberger-Private
▪ Logging behind casing…mostly with open hole logs….with its own value and limitations.
Petrophysics Logging Behind Casing
Sigma and Full Spectroscopy Large
Pulse neutron and Spectroscopy Slim
Pulse neutron, Inelastic GR, Full Spectroscopy Slim
0 5 10 15 20
CH res. slim
CH resistivity large
CH Density
Acoustic Wide Band Frequency
Acoustic Slim
Neutron Poro Thermal
Neutron Porosity Epithermal
Spectral Gamma Ray
Gamma Ray
Casing or hole size rangeCasing / Completions
Single Multiple
×× ×× ×××× ×× ××××× ×× ×
Schlumberger-Private
Needs to consider many diverse conditions
▪ Open hole log availability: yes/no
▪ Formation water salinity: fresh/saline, known/unknown
▪ Lithology: known/unknown, simple/complex
▪ Hydrocarbon type: oil, gas, mixed, kerogen?, bitumen?
▪ Other: CO2; dynamic conditions,…
Saturation
1. Sigma
2. Sigma + Resistivity
3. Carbon/Oxygen
4. TOC
5. FNXS
Petrophysics Logging Behind Casing
Schlumberger-Private
▪ Water saturation when formation water salinity has sufficient contrast with hydrocarbon and rock
▪ Lithology and porosity effects
Water Saturation from Sigma Log
Slog = Vmatrix * Smatrix + Vclay* Sclay + fSw Sw + f(1-Sw) Sh
MaterialSigma (c.u.)
TPHI
Quartz 4.55 –0.03
Calcite 7.08 0.00
Dolomite 4.70 0.03
Wet Illite 21.00 0.34
Kerogen (CH 1.3g/cm3) 20.18 0.98
Water 22.20 1.00
200ppk NaCl water 99.9 0.93
Diesel (CH1.8 0.89 g/cm3) 23.30 1.08
CH4 (0.15 g/cm3) 7.50 0.21
CO2 (0.6 g/cm3) 0.03 –0.12
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Saturation from Sigma in Depleted Reservoirs; Complex Wellbore configuration
Raw Measurement Interpretation Saturations
Depleted zone
Saturation at original condition
Tubing, Casing (in) Borehole (in)
7 (casing) + 9-7/8 (Casing) 12.25
• Formation type: Clastic, 20% porosity; 50ppk salinity (found
to be variable)
• Borehole fluid CaBr2 and formation oil; chrome tubing
Formation salinity change; fresher
Tubing, Casing (in) Borehole (in)
4.5 (Tubing),
7 (casing) + 9-7/8 (Casing)
12.25
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▪ Classical measurement for cased hole reservoir monitoring of oil content and fresh water conditions
▪ Rw independent
Dynamic range
function of porosity
and oil carbon density
Oil Saturation from Carbon/Oxygen Logging
FCOR vs NCOR
(Yields)
Carbon/Oxygen
Schlumberger-Private
Oil Saturation from Cased Hole Carbon/Oxygen Spectral Analysis
▪ Shaly sand formation; low unknown salinity
▪ Bypasses oil from Carbon/Oxygen logging in absence of complete open hole logs – standalone cased hole evaluation
Cased
hole FE
Far and Near C/O
Yields Ratio
Oil Volume and
Saturation from C/O
Schlumberger-Private
▪ Total Carbon (TC) is measured;
▪ Minerals are computed
▪ Inorganic carbon is calculated from mineralsTIC = 0.120*Calcite + 0.130*Dolomite + 0.104*Siderite + 0.116*Ankerite
Inorganic Carbon from Minerals
TOC
MineralsCarbon
TC TIC- = S(oil)
Shc =TOC · rma · (1-fT)
rhc · Xhc · fT
Oil Saturation from Spectroscopy (TOC)
▪ Organic Carbon (TOC) = TC - TIC
▪ S(oil) is computed from TOC and Porosity
Elements,
Matrix,
Minerology,
Full Closure Spectroscopy
SPE # 166297, 2013
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Oil Saturation from Cased Hole In-Situ Total Organic Carbon Measurement
▪ Shaly sand formation; low unknown salinity
▪ Bypasses oil from Carbon/Oxygen logging in absence of complete open hole logs – standalone cased hole evaluation
Cased
hole FE
Far and Near C/O
Yields Ratio
Oil Volume and
Saturation from C/O
Shc =TOC · rma · (1-fT)
rhc · Xhc · fT
SPE # 186957-MS 2017
Schlumberger-Private
TOC Independent Oil Volume in variable Salinity and Porosity
8.75” BS; 7” Casing; 50 ft/hr
Neutron
Density
Spectroscopy,
C/O
CH Shc
0 1
Cased Hole
Open Hole
Volumetric
interpretation
N-D
Porosity
50 p.u. 0
Porosity
50 p.u. 0
Spectroscopy
Oil wt%
0 wt% 18
Spectroscopy
Dielectric
OH Shc
0 1
100 ft
• Heavy oil under steam-injection (EOR)
• N-D crossover
• Resistivity fails
• Oil Saturation from TOC in good
agreement with C/O analysis
• Solving for complex mineralogy
Schlumberger-Private
▪ Critical present day oil saturation from TOC
▪ FSAL estimate from Sigma, also shedding light on the complex reservoir environment
Petrophysics and well integrity logging behind 11.875in casing; in front of 14.5in bit size
High Def spectrosco
py
Well integrity
Formation testing
Cased Hole Spectroscopy in large hole – 9 Years After Drilling
XX600
XX500
XX400
XX300
XX200
XX100
XX000
XX700
Schlumberger-Private
▪ Probability of fast neutrons to interact with atoms; directly sensitive to gas filled porosity
▪ Quantify gas volume in low porosity rock together with Sigma and neutron porosity logs.
Gas Saturation from Fast Neutron Cross-section New Measurement
Detected
inelastic GR
0 0.2 0.4 0.6 0.8 15
5.5
6
6.5
7
7.5
8
8.5
HI
FN
XS
(1
/m)
fresh water
CH4 (0.1g/cc)
Sg 0%
Sg 100%
Schlumberger-Private
Saturation from Gas (FNXS) Inelastic hydrogen in Tight Gas Sand
Producing oil and gas field; shaly sand formation with low porosity gas-filled and very low porosity alternating.
8.75-in bit size, 4.5 in casing; 11.6 lbm/ft casing weight with cement thickness more than 2 in.
Mineral Solver
FNXS
TPHISIGM
claygaswaterquartz
clayclaygasgaswaterwaterquartzquartz
clayclaygasgaswaterwaterquartzquartz
clayclaygasgaswaterwaterquartzquartz
VVVV
FNXSVFNXSVFNXSVFNXSVFNXS
TPHIVTPHIVTPHIVTPHIVTPHI
SIGMAVSIGMAVSIGMAVSIGMAVSIGMA
+++=
+++=
+++=
+++=
1
Schlumberger-Private
o Shaly sand, variable rock quality;
o Casing and tubing, open perforations; crossflow conditions
o FNXS Fast Neutron Cross Section; environmental corrections applied to
account for different conditions than EECF.FNXS vs TPHI analysis value
Sg
0%
Sg 100%
Fast Neutron Cross Section Measurement Applied to Petrophysics
Schlumberger-Private
Three Phase Saturations Computation in Carbonate
Differentiate Gas Filled Porosity from oil filled rock; variable porosity
Mineral Solver
FNXS
TPHI
Elements Dry
Weights
SIGM
Standalone cased hole evaluation
calcitegaswaterquartz
quartzquartz
calcitecalcite
calcitecalcitegasgaswaterwaterquartzquartz
calcitecalcitegasgaswaterwaterquartzquartz
calcitecalcitegasgaswaterwaterquartzquartz
VVVV
DWSIVDWSI
DWCAVDWCA
FNXSVFNXSVFNXSVFNXSVFNXS
TPHIVTPHIVTPHIVTPHIVTPHI
SIGMAVSIGMAVSIGMAVSIGMAVSIGMA
+++=
=
=
+++=
+++=
+++=
1
Schlumberger-Private
ELAN Multi-mineral analysis integrating
Pulsar measurements
• Standalone evaluation of rock and fluids, through quantitative use of FNXS with Sigma, TOC, and full spectroscopy recorded behind
casing
• Multi-mineral solver plot with reconstructed curves and computed rock and fluid volumes:
Mineral Solver
FNXS
TPHI
Elements Dry
Weights
SIGM
Three Phase Saturations behind Casing and Another Complex scenario
SPWLA 58th, 2017 – Solving for reservoir saturations using multiple formation property measurements from a single PNL tool
Schlumberger-Private
Saturation Calculation and Monitoring Behind Casing - Summary
Condition SIGM RT C/O TOC FNXS Remarks
f<15% (low f) Limit on RT,max
15%<f, Csalt<20 ppk (fresh) Limit on RT,max
15%>f, Csalt>20 ppk (saline) Favorable contrast conditions
Mixed salinity Need Csalt profile
Flowing well Need Yo measurement
Fluid contact in hole Inaccurate near contact
Washed-out holes Shallow DOI on C/O
Near wellbore effect Shallow DOI on C/O
Acid effect Effect of high S acid element
Run in small tubing Slim measurement available
Multiple casing/tubing string with good calibration
Deviated/HZ well Conveyance dependent
Lithology Need matrix data
Ref.: after Aulia et al., 2001 (Schlumberger) - extended
State of art technology and Integrated approach help reducing Sw uncertainty in complex setting
Schlumberger-Private
• Alternative methods for saturation measurement from logs behind casing and within completion exist.
• The results can be obtained as a standalone measurement approach or data integration to open hole.
• The choice of the logging program and computational workflow depends on the logging environment and its complexity; and the particular evaluation objective.
Conclusions
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Paper # • Paper Title • Presenter Name
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