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José Vásquez Senior Petrophysicist
12 July 2017
Gestión alternativa de Saturación de crudo en reservorios de agua fresca. Ejemplos del Este de Colombia
Presenter: Jose Vasquez
Studies:
• Mechanical Engineer
• BSc Forestry Engineering
• MBA
Schlumberger
• 15 year in Wireline (data acquisition)
• 8 years as Field Engineer
• 7 years in management, sales & technical support
• 8 years in PetroTechnical Services
(log data processing and interpretation)
• OH Interpretation
• CH Interpretation
MOTIVATION
Dealing with Oil Saturation computation in fresh water reservoirs?
Low sensitivity to Sw
of conventional methods. Eastern Colombia
… but as you will see, not only for fresh water
Dealing with Oil Saturation computation in fresh water reservoirs?
Fresh Water HC Colombian Reservoirs This case is based on SPE paper SPE-177095. Thanks to Ulises Bustos, Schlumberger Petrophysicist for sharing his knowledge and the related material.
Driver
• SW • Primary objective in reservoir evaluation
• Economics of a project
• Mandatory
• Accuracy
• Low Uncertainty
Poor Precision
Accurate
Yields
Good Precision
Inaccurate
Windows
Driver (2)
• Historically, Sw based on resistivity • Archie
• Or derived forms of Archie
• Limitations in Colombian Reservoirs
• Fresh Water (<10,000 ppm)
• Variable Clay Mineralogy
• Carbonate Cements
• HC with wide range of composition
• Gas
• Light Oil
• Heavy Oil
• Movable oil identification is critical factor
Driver (3)
• Siliclastic reservoir rocks with variable matrix properties • Impact on formation porosity
• Drilling Challenges • Active Tectonism
• Significant variations in stress fields
• Depleted reservoirs in mature fields
• Narrow window for drilling
• Higher risks for OH logging (WL or LWD)
Driver (4)
• Wells drilled without any logging • Risk reduction
• Cost reduction
• CH logging provides the only evaluation option
• HC evaluation
• Reservoir Volumetric determination
• Reservoir management
• Economics
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
300 3000 30000 300000
UNCERTAINTY OF SW VS SALINITY MIN DISTR. RANGE MAX DISTR. RANGE
FSAL [ppm]
Sw [v/v]
Understanding sensitivity to Sw The problem of conventional analysis in fresh water
Existing Techniques
• C/O Logging • Common techniques CH logging in Colombia
• High statistics, calibration
• Slow acquisition
• Slim, Large Borehole effect
• >15% Porosity
• Requires Lithology knowldege
Source: Oilfield review,
Summer 1996
Fanny-1 well, Ecuador
Existing Techniques (2)
Sigma Logging
• Sigma = f(Chlorine) • Requires FSAL
• Poor sensitivity to HC in fresh water or variable salinities.
• Requires accurate knowledge of Sigma Matrix
• Requires good knowledge of PHIT
• Very limited applications in most of on-shore Colombian reservoirs
Application of Advanced Spectroscopy
• New methodology for Hydrocarbon Saturation from: • Advanced spectroscopy measurements
• Total Organic Carbon (Cradock et. Al, 2013)
• PHIT
Source: Oilfield Review
Application of Advanced Spectroscopy
• Advantages compared to previous C/O logging interpretation methods: In the new method Saturation is: • based on the conversion of dry weight organic to
hydrocarbon saturation and does not require an extensive calibration database.
• Independent of salinity effects
• Independent of clay or other lithology effects
Hydrocarbon Saturation (Sh) from TOC
• TOC found primarily in: • Kerogen
• Bitumen
• Hydrocarbons
• Oil
• Gas
Photomicrograph Showing Type II Kerogen
• In Unconventional reservoirs • TOC becomes a critical
determination for pay zones identification
• In conventional reservoirs • TOC is occupying pore space
• VHC within Porosity
From TOC to Hydrocarbon Saturation (Sh)
• TIC = (0.12 Wcalcite + 0.13 Wdolomite + 0.104 Wsiderite + …)
• TOC = TC – TIC
• TOC = MCorg / Mma
• MCorg = Xhc * Mhc
• Mhc = ρhc * Vhc
• Shc = Vhc / ФT
From TOC to Hydrocarbon Saturation (Sh)
• Shc = Vhc / ФT
• Shc = Mhc / (ρhc * ФT )
• Shc = Mcorg / (Xhc * ρhc * ФT )
• Shc = TOC * Mma / (Xhc * ρhc * ФT )
• Shc = TOC * ρma * Vma / (Xhc * ρhc * ФT )
Shc = TOC * ρma * (1 - ФT ) / (Xhc * ρhc * ФT ) Measured by
Advanced
Spectroscopy
Hydrocarbon
properties
Measured by porosity tool
Case Study #1: Open Hole Dielectric-Spectroscopy
TOC
Lithology
Saturations Salinities
Dielectric Dispersion
A
B
Oil ?
Water?
Contacts?
Oil_Dielec-1 in. DOI
Oil_Dielec-4 in. DOI
Oil_Spectros-10 in. DOI
Spectroscopy-Dielectric: Deeper Saturation
Profiling to understand Oil Mobility
Sw from RT
Dielectric basic Principle & application
Principles:
• Multifrequency EM signal
107 – 109 GHz
• Water: high permittivity
• Sensitive to Water Volume
Applications / Capabilities:
• Water filled Porosity
• Water Salinity
• Clay CEC
• Textural Parameters: m & n
• Anisotropy
• High Resolution (2 & 4”)
Case #2: Open Hole Spectroscopy reveals high matrix density, complex lithology and otherwise bypassed oil
Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison
Conventional slim C/O log
• 3 passes @ 100 fph
• 25 hours log plan
• 70-80% oil Saturation
• Sgas= 0%
Central Southern Colombia
Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison
Advanced
Spectroscopy in CH
• 1 Single Pass @
530 fph.
• < 2 hours log
• Reasonable
agreement with
conventional slim
C/O.
• In zone C higher
So is obtained.
Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison
Time efficient
results obtained
with advanced
spectroscopy.
• Good
agreement
when compared
to slim C/O
• 10 times faster
• Detailed
lithology
• TOC
Case #4: Cased Hole Light Hydrocarbon sands & complex lithology
Only zones A &
B with So ~50-
65%
Change in
Salinity above X
Complex
lithology with
Matrix density
higher than 2.65
g/cc