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Optimizing Pulsed Neutron Capture (PNC)
Logging and Modeling Techniques in Low
Porosity and Active CO2-EOR FieldsAmber Conner (Battelle) and David Chace (Baker Hughes, Inc.)
[email protected] [email protected]
1
Acknowledgements
− Midwest Regional Carbon Sequestration Partnership (MRCSP,
www.mrcsp.org) is funded by the DOE DOE/NETL under cooperative
agreement – DE-FC26-0NT42589.
− Site host Core Energy, LLC – Bob Mannes, Rick Pardini, Allen
Modroo, and team.
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− Baker Hughes – David Chace and Abou
Saleh Jehad, working with triangulation
and 3-phased analysis methods.
− Mark Kelley, Matt Place, Caitlin
McNeil, Jackie Gerst, Autumn
Haagsma, Neeraj Gupta, and the
Battelle MRCSP team.
Outline
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MRCSP – Why we use Pulsed Neutron Capture (PNC)
− Large-volume potential
− Geologic background
− Cased-hole logging
PNC
− PNC tool
− Limitations
− Model inputs
Improving the Analysis
− Triangulation method
− Improve saturation estimates
− Challenges
Additional Benefits
− Characterizing geology
− Reduce uncertainty in capacity models
MRCSP Michigan Basin Large Scale Test
Northern Niagaran Reef Trend
− Large-volume potential.
− MRCSP Goal – inject and monitor at
least 1 million metric tons of CO2 across
multiple reefs.
− 550,000 metric tons of CO2 injected to
date
4
Stratigraphy of Zone
of Interest
Northern Niagaran Reef Trend
- Primary oil/gas and reservoir targets are A-1
Carbonate (Ruff) and Brown Niagaran
(Guelph) formations.
- Brown Niagaran ranges from primarily
dolomite, closer to the barrier reef, to
primarily limestone more basinward.
- Niagaran has well-developed intercrystalline
and vuggy porosity.
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Silurian Carbonate Reef Trend
Several Technologies Tested
- Focus on pulsed neutron capture (PNC).
PNC Logging for Monitoring Saturation Levels and
Wellbore Conditions
Detectors
Source
Neutron
Burst
Neutron
Thermalization
RIN13, RATO13, and
Sigma Curves
PNC Tool
PNC Log
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Pulsed Neutron Capture (PNC)
- Effective method for verifying
containment in the near
wellbore environment.
- Provides monitoring of oil, gas,
and water saturation levels.
- Facilitates CO2 saturation
evaluations oil/gas/water
- Inexpensive to deploy?
Traditional Limitations
- <10% porosity for PNC logging
- <50,000 ppm salinity
- Does not differentiate between
CH4 and CO2
PNC Logging – Initial Model
50
60
70
80
90
100
5600 5700 5800 5900 6000 6100 6200 6300 6400
Gas Saturation Year 1 Gas Saturation Year 2Baseline Gas Saturation
Baseline
− Limited to a gas and water analysis.
− Lack of oil saturation.
− Does not show CH4 and CO2 separation.
Repeat Logging
− Repeat conditions were logged using the same completion
configuration as the baseline log.
− Lack of gas increase between baseline and repeat logs.
− Does not show CH4 and CO2 differences.
Repeat Gas Saturation
Gas saturation increased between baseline and repeat logging
Depth (ft.)
Pe
rcen
tage (
DE
C.)
Sigma 2012
Sigma 2013
0 100
1000
Water
Gas
Gas Saturation
Analysis
Correlation
0 100
0 100
0 5
0 5
3500 8000
0 100
Gamma Ray 2013
Gamma Ray 2012
(gAPI)
(gAPI)
(gAPI)
(feet)
(gAPI)
(degree)
RBOR 2013
RBOR 2012
TVD
Deviation
PNC Data Analysis – Updating Modeling Inputs
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PNC
Lithology
Completion Configuration
Cement Bond
Fluid Properties
Limits
Components for Model
− Sandstone, limestone, or dolostone.
− Core or log analysis.
− Bit size, borehole fluid, casing/tubing size.
− Cement bond logs.
− Determine the percentage of cement
bond.
− Fluid properties: water salinity, oil density,
gas composition.
Reduced Limitations
− >3% porosity fields: higher salinity fields
compensate for low porosity.
− >200,000 ppm salinity.
− Gas sampling vital – PNC does not
differentiate between CH4 and CO2.
Resolution – Water, Oil, Methane, CO2RIN13
RATO13
Sigma
Water
Oil
Methane
CO2
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RIN13
− 6”-10” depth of investigation.
− Salinity independent.
− High separation between
liquid and gas.
− Provides better resolution in
low porosities.
RATO13
− 12”-16” depth of investigation.
− Salinity and oil density
dependent.
Sigma
− 12”-16” depth of investigation.
− Poor separation between oil
and gas.
Triangulation – Sigma (SGFC) and RATO13
Corrected RATO13 and
Theoretical Sigma
- RATO13 vs Porosity and Sigma
vs Porosity.
- Porosity guides are determined
by highest porosity
indicators in the zone of
interest.
- Water, oil, and gas are the key
saturations of interest for
EOR fields and CO2 storage.
Modeling Inputs
- Triangle size and shape is
driven by inputs – casing
and hole sizes, borehole
fluids, porosity, and lithology.
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Water
Oil
Gas
Triangulation -
Output
Sigma and RATO13
- At this depth (yellow dot) –
predominately gas with
some oil saturations.
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Water
Oil
Gas
Depth
Triangulation –
Output Continued
Sigma and RATO13
- At this depth (yellow dot) – oil
and water saturations with
some gas.
12
Water
Oil
Gas
Depth
PNC Log
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0
0.2
0.4
0.6
6100 6200 6300 6400 6500 6600 6700 6800 6900
Gas Saturation 2012 Gas Saturation 2014Baseline Gas Saturation
Gas saturation increased between baseline and repeat logging
Repeat Gas Saturation
Depth (ft.)
Pe
rcen
tage (
DE
C.)
Baseline Analysis
− Oil dominates in high porosity intervals in
baseline logs.
− Oil, gas, water saturations.
− Fluid sampling establishes estimations of
CH4 for baseline logging.
Repeat Analysis
− Oil and gas dominates in high porosity
intervals.
− Yield increase in gas saturation due to
swept oil.
− Does not differentiate CH4 and CO2
differences.
PNC – New Model
Gas Increase
Cement Bond– Complications
CBLPNC Log Before
Cement ModelingPNC Log After
Cement Modeling
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Data Analysis
- Less than 75% cement quality
creates overestimation of fluid
saturations
- Attenuation of Less than 75%
cement intervals incorporated
in new PNC model are not
always reliable.
Gas Artifact
PNC
Lithology
Completion Configuration
Cement BondFluid
Properties
Limits
The Salt Plug Challenge
Salt Plug
- Seawater evaporation after death
of a reef.
- Large vugs can sometimes be
filled with salt.
- Difficult to predict and hard to find
in mixed carbonate reefs.
- Widespread
- Halite can show potential porosity
in wireline logs – neutron
porosity and bulk density.
- Can lead to overestimating
reservoir storage potential.
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Salt in A-1 Carbonate
Silurian Carbonate Reef Trend
16
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Bulk Density of Salt Plugged Carbonate
2% porosity_dolomite
4% Porosity_dolomite
6% Porosity_dolomite
8% Porosity_dolomite
10% Porosity_dolomite
2% porosity_limestone
4% porosity_limestone
6% porosity_limestone
8% porosity_limestone
10% porosity_limestone
Bu
lk D
en
sity (
g/c
m3)
% Salt
Bulk Density in Mixed Carbonates
Challenge
- Difficult to differentiate
between carbonates
and salts in different
porosities.
- Narrow separation
between bulk
density and
percentage of salts.
Sigma – Salt Plugging in the Silurian Reefs
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Salt in Brown Niagaran
Salt in A-1 Carbonate
A-1 Carbonate
- Correlation between
gamma ray and
sigma cannot
determine where salt
plugged intervals
occur.
- Salt plug occurs in the
upper interval of the
A-1 Carbonate and
has a salt stringer
below.
Brown Niagaran
- Gamma Ray signature is relatively low.
- Salt plug occurs in the upper interval of
the Brown Niagaran.
Brown NiagaranA-1 Carbonate
A-1 Evaporite
Summary
−Applied PNC logging in low porosity EOR fields.
−Traditional 2-Phase analysis was evolved to a 3-Phase analysis.
− Enhanced the modeling inputs and used new triangulation method.
− Provide better estimations of oil, gas, and water saturations.
− Improve monitoring of CO2 gas and can enhanced modeling of CO2.
−PNC used to interpret salt plugged carbonates which can
improve reservoir capacity models.
−The MRCSP program has afforded the opportunity to optimize
PNC logging and the development of a “best practices” plan to
implement PNC monitoring in low porosity and EOR production
fields.
−Currently working with resistivity, pressure data, and elemental
capture spectroscopy.
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Extra Slides
20
A-2 Carbonate
A-2 Evaporite
A-1 Carbonate
Brown Niagaran
Low Porosity
High Porosity
PNC logging baseline wellbore analysis
Baseline Models
• Threshold porosities for PNC
analysis is 3%
PNC
Lithology
Completion Configuration
Cement BondFluid
Properties
Limits
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The MRCSP is assessing viability of carbon sequestration
DOE-Funded
- One of seven DOE-funded regional
partnerships to develop infrastructure
for wide-scale CO2 sequestration
deployment
Characterization Phase
- Characterization phase (2003 – 2005)
and validation phase (2005 – 2010)
completed
MRCSP Development Phase
- (2010 – 2019) focusing on CO2 utilization
and storage in carbonate reefs
- Late-stage EOR
- Operational EOR
- Newly targeted
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