geocsi solving gas migration problems wbpc 2015
TRANSCRIPT
Making chemistry data meaningful
“Geo-CSI” in the oil patch – how advanced geochemistry solves real
world problems
© 2015 Chemistry Matters Inc.
Scott Mundle* and Court Sandau
WBPC, Regina, SK, April 28-30, 2105
Presented at the Williston Basin Petroleum Conference, Regina, SK April 28-30, 2015
o Geochemical characterization of sources to identify ‘fugitive’ gas migration in the oil/gas sector
“Geo-CSI”
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 2
o Surface casing used to protect shallow (potable) aquifers
o Gas (and water) in SCVs migrate from deeper zones (cement failure)
o Irregular and low flow rates (can be difficult to sample/monitor)
o How can you determine the source(s) of the leaks?
Surface casing vent flow
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 3
Geochemical characterizations & forensics
o Gases/fluids for different zones can be ‘fingerprinted’
o But why do you keep getting burned with this approach?
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 4
The geochemistry is never wrong, but the interpretation is often incorrect
o Common problems: o Sample degraded prior to
analysis o Either the wrong ‘end-
members’, or no ‘end-members are used to identify sources
o Numbers are reported that are at or below the detection limits of the instrument
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 5
Don’t make assumptions based on regional geochemistry
o Where do the ‘fingerprints’ originate?
o Commercial isotope “databases” often use regional values rather than local values that can mislead interpretations
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 6
Need high quality SCV samples
o Can separate and collect gas and liquid o Gas can be purged to remove “breathing”
gas from well o Need low atmospheric content in gas
samples for compositional and isotopic characterization
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 7
Sampling can affects water chemistry
0.0001$
0.001$
0.01$
0.1$
1$
10$
100$
1000$
10000$
100000$
Lithium
$Sodium
$Po
tassium$
Rubidium
$Ce
sium$
Beryllium
$Magne
sium$
Calcium
$Stron=
um$
Bariu
m$
Boron$
Alum
inum
$Ga
llium
$Indium
$Thallium$
Silicon
$Ge
rmanium$
Tin$
Lead$
Phosph
orus$
Arsenic$
An=m
ony$
Bism
uth$
Sulphu
r$Selenium
$Telluriu
m$
Chlorin
e$Brom
ine$
Iodine
$
Scandium
$YD
rium$
Titanium
$Zircon
ium$
Vanadium
$Niob
ium$
Tantalum
$Ch
romium$
Molybde
num$
Tungsten
$Mangane
se$
Iron$
Cobalt$
Nickel$
Palladium
$Pla=
num$
Copp
er$
Silver$
Gold$
Zinc$
Cadm
ium$
Mercury$
Lanthanu
m$
Ceriu
m$
Praseo
dymium$
Neod
ymium$
Samarium$
Europium
$Ga
dolinium$
Terbium$
Dysprosiu
m$
Holm
ium$
Erbium
$YD
erbium
$
Thorium$
Uranium$
BleedNbarrel$FlowNthrough$Cell$
1 2 3 4 5 6 7 d-block f-block
Group 2 metals and f-block metals lower in bleed barrels - suspended solids settle out in bleed barrel (low energy environment)
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 8
Sample integrity: The gas bag
• Over time isotopic composition of methane and CO2 changes • Methane artificially appears more ‘thermogenic’ • Shift in CO2 is less predictable
• Manufacturer recommendations - analyze within 48 hours
© 2015 Chemistry Matters Inc.
*Arrows not to scale
WBPC, Regina, SK, April 28-30, 2105 9
How can you get it right every time?
Mudgas Geochemical Profile Characterized stratigraphy
Production and Potential Source Zones: 1.) Fluids 2.) Gases Characterized end-members
Shallow Fluids 1.) Surface water 2.) Groundwater Characterized inputs
SCVs: What are the Source(s)? 1.) Fluid 2.) Gas
GEOCHEMISTRY:
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 10
Complex case study: Fluid and gas flows
• Collected four samples from each location: – SCV gas sample – SCV liquid sample – Production casing gas sample – Production casing liquid sample
• Used local groundwater and deep aquifer wells in region for comparison
• Used perforated wells with DST samples to acquire ‘end-members’ for other potential source zones
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 11
No insight from water isotopes
o Water isotopes implicated groundwater sources that conflicted with other indicators (chlorides, TDS, etc.)
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 12
A clearer picture with advanced analyses
o Different sources had characteristic ranges of concentrations and isotope values
o Provided first line of evidence to indicate that different source zones can be identified
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 13
Identifying source zones
o Fluids provide a line of evidence for potential sources, but they do not provide a refined interpretation
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 14
Combined fluid and gas characterization
*Exact values property of client, shift in isotope values indicated
δ13C Values GASES C1 C2 C3
SCV A - 1.9 B - 2.3 C Casing A* B* C*
o Gases provide a second line of evidence for potential sources and help confirm a production zone leak
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 15
Complete geochemistry = complete picture
δ13C Values GASES C1 C2 C3
SCV A - 1.9 B - 2.3 C Casing A* B* C*
*Exact values property of client, shift in isotope values indicated
δ13C Values GASES C1 C2 C3
SCV A - 13.1 B - 8.1 bdl Casing A* B* C* o Gases provide a second line of
evidence to confirm a cretaceous zone leak
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 16
δ13C Values GASES C1 C2 C3
SCV A - 13.1 B - 8.1 bdl Casing A* B* C*
Identification of depth of source zone
o Mudgas log can refine cretaceous leak to within 200-300m range
© 2015 Chemistry Matters Inc. WBPC, Regina, SK, April 28-30, 2105 17
Where can it go wrong?
• Similar isotope ‘fingerprints can be expected
• Need to account for this complexity in the interpretation WBPC, Regina, SK, April 28-30, 2105 18
Best practices for ‘geoforensics’
• Collect high quality samples • Collect samples for potential source(s) and from the
production casing (if possible) • Ask the right questions and get it right !
– What source zone characterizations were used in the interpretation? – Where were these source zones characterized (geographically)? – What are the reliable detection limits for your instrumentation?
High quality samples, isotope analysis and accurate interpretation of microbial effects provide more
conclusive source determination.
WBPC, Regina, SK, April 28-30, 2105 19
