GeoConvention2016_Identifying Surface Casing Vent Flows (SCVF) Using Geoforensics

©2015ChemistryMa2ersInc. 1GeoConven)on2016–www.chemistry-ma:ers.com

Makingchemistrydatameaningful

Characterizingthesourcezonesforsurfacecasingventleaks

CourtD.Sandau,PhD,P.ChemMarch8,2016–GeoConvenCon2016,Calgary,AB

©2015ChemistryMa2ersInc.

Acknowledgements

2

•  Sco:Mundle,PhD,C.Chem,P.Chem

GeoConven)on2016–www.chemistry-ma:ers.com

•  Livetweets:#GeoCon2016and#GeoForensics


SurfaceCasingVentFlowsandGeoforensics

3GeoConven)on2016–www.chemistry-ma:ers.com


Geoforensics


Introducing a new term: Geoforensics •  Forensics is derived from latin “forens”, meaning of, belonging

to the forum, public

•  Geoforensics is the application of scientific methods used to identify source(s) of chemical constituents (natural or man made) in fluids (gases, groundwater, oil), soil and/or rock from the subsurface of the Earth for use in potential litigious issues or for public debate or discussion.


SurfaceCasingVentFlows(SCVFs)


SCVFs come in many shapes and sizes -  High pressure and intensity are generally easy to

identify (e.g. EOR fields) -  Low flows/pressures provide difficult sampling

opportunities (Houdini wells – “no you see them, now you don’t” -  L.F. 2012 – “Flow’ers and Show’ers”


WhatdoSCVFslooklike?


Steam

Oily Bubbles Intermittent Flow Constant Fizz


o  Surface casing used to protect shallow (potable) aquifers

o  Fluids(gas and/or liquid) migrate from deeper zones through SCV

o  Gas migration occurs outside the SCV

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 and gas migration

GeoConven)on2016–www.chemistry-ma:ers.com 7


o  Geochemical characterization of sources to identify ‘fugitive’ gas migration in the oil/gas sector

Geochemical ‘fingerprinting’



GeochemicalcharacterizaJons&forensics

o  Gases/fluids for different zones can be ‘fingerprinted’

o  But why does this approach sometimes fail?



Thegeochemistryisneverwrong,buttheinterpretaJonisoPenincorrect

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 Misinterpretation of the data (e.g. not noticing altered fingerprints, or using wrong data)



Don’tmakeassumpJonsbasedonregionalgeochemistry

o  Where do the ‘fingerprints’ originate?

o  Commercial isotope “databases” often use regional values rather than local values that can mislead interpretations



SamplingandDataAcquisiJon–Step1



Need high quality SCV samples o  Can separate and collect gas, liquid and

steam o  AER is considering requirement for

monitoring SCV flow in SAGD wells, what about steam?

o  Need low atmospheric content in gas samples for compositional and isotopic characterization

Steam



Samplemediacanaffect‘fingerprints’

•  Over time isotopic composition of methane and CO2 changes •  Methane artificially appears more ‘thermogenic’ •  Shift in CO2 is not predictable

•  Manufacturer recommendations = analyze in 48 hours



GoalforGasSampling

•  Maximizegasconcentra)on–  Leastamountofairaspossible–  Purgeairfrom“system”,allowgastoaccumulateifnecessary

•  Eliminatemoisture–  Breakoutwaterorsteam

•  Preservesampletopreventdegrada)on

•  Analyzesamplewithinhold)me–  48hoursforbags



LiquidsSampling

•  Slow/lowvolumeliquidventflowsproblema)csampling

•  Requirespassivesamplingtopreservechemistryoftheliquid


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


BestPracJcesRequiredforSCVFSampling

•  Bantheterm“Grabasample”•  Samplinggasesissamplingtheinvisible

–  Needgoodconnec)ons/seals–  Leaktests(checkconnec)ons)–  Ensuresampleintegritymaintained

•  Samplingliquids–  Easiertosample,some)meshardertocollect–  Passivecollec)onsystems,butprotectedfromenvironmental

degrada)on

•  Higherqualitydata=Higherchanceforsuccess!



IdenJficaJonandCharacterizaJonofSourceZones



HowcanyougetitrighteveryJme?

Mudgas Geochemical Profile Characterized stratigraphy

Prod./Source Zones: 1.) Fluids 2.) Gases Characterized end-members

Shallow Fluids 1.) Surface water 2.) Groundwater Characterized inputs

SCVs: Identify matrix 1.) Fluid 2.) Gas

GEOCHEMISTRY:



CaseStudies–UsingEnd-MemberstoIdenJfySCVFs



CaseStudy•  Collectedfoursamplesfromeachloca)on:

–  SCVgassample–  SCVliquidsample–  Produc)oncasinggassample–  Produc)oncasingliquidsample

•  Usedlocalgroundwateranddeepaquiferwellsinregionforcomparison

•  Targetedsourcezones(end-members)weresampledandcharacterized

•  FullMGILforregion



Conservative Chemistry

o  Characterization of SCV fluids focused on both routine and ‘conservative’ analytes:

•  pH, alkalinity •  Concentrations of dissolved cations and anions •  Extended metals (65 in total) •  Stable isotopes (18O, 2H, 11B, 13C, 34S, 37Cl, 81Br, 87/86Sr)

•  Conservative isotopes were required for the following cases to elucidate fluid source due to pH alteration of all susceptible analytes



SCVF Analysis o  Specific conservative isotopes and their analyte

concentrations were discovered to be characteristic of specific formations.



SCVF – Example 1

Conclusion: o SCV leak is from production zone

o Gas is entirely production formation o Water is production zone mixed with

intermediate GW

C1 C2 C3 CO2

SCV -51.9 -45.4 -35.9 bdl Casinggas -50.0 -43.1 -35.9 -2.5

Isot

ope

valu

e

Concentration value

Gas Results

Liquid Results


Mississippian Cretaceous

Mississippian

Cretaceous


SCVF – Example 2

o Gas/liquid origin not from production zone o Based on MGIL, 300-400 m origin

Conclusion: o SCV leak is from shallow zone

C1 C2 C3 CO2

SCV -61.7 -48.0 bdl bdl Casinggas -48.6 -39.9 -36.6 -18.8

Isot

ope

valu

e

Concentration value

Gas Results

Liquid Results


Mississippian Cretaceous

Mississippian

Cretaceous


Best Practices for SCVF Sampling •  Collecthighqualitysamples–protectedfromdegrada)on,purgegaspriortosampling,etc.

•  Preservesamplesinthefield•  Collectpoten)alsourcesamplesandfromtheproduc)oncasing(ifpossible)

•  Usebasicchemistrybutifnotuseful,mayneedconserva)veanalytes

•  Conserva)veanalytescanprovideclarityfordifficultSCVfluidsamples



Best Practices for Identifying SCVF •  Propersamplingandcharacteriza)onofpoten)alsourcezones(gasandliquids)

•  SolidMGILforthearea•  Gooddatabasefortheareaofsuccessfulinterven)ons

•  Geochemistrydataisalwaystellingyousomething,interpre)ngthemessageiskey!



Thank you for your attention Contact Info: Chemistry Matters Inc. Court Sandau Cell: 403.669.8566 Email: [email protected] URL: chemistry-matters.com Visit my website and sign up for email for automatic receipt of my blogs!

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GeoConvention2016_Identifying Surface Casing Vent Flows (SCVF) Using Geoforensics

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