6th Well Bore Integrity6th Well Bore IntegrityNetwork Meeting

Alberta ERCBInvestigation of the Joslyn Creek SAGD Surface Steam Release of May 18 2006Surface Steam Release of May 18, 2006

The Hague, The NetherlandsApril 28-29, 2010

Dr. Fran Hein, P.Geol.Chief Geologist, ERCB

• Catastrophic explosion l ti f i t

Bulletin 2010-10 Investigation The Steam Release

lasting ~ few minutes. • Surface crater disturbance ~

125 m by 75 m.S f lif & b id• Surface uplift & subsidence.

• Tensile cracks & rotated ground.

• Ejection significant volume of soil, caprock, bedrock & bitumen dust.

• Boulders & rocks travelled ~300 m horizontally and at least that vertically.T t l l f di l d

• Blowouts rare in Alberta. 2008:0.118/1,000 non-aband.wells.I 2009 ERCB h d 21 578 fi ld• Total volume of displaced

material overlying soil ~ 1400 - 1700 m3.Si ifi t b f

• In 2009 ERCB had 21, 578 field inspections @ energy facilities.

• Joslyn Creek: Only time a • Significant subsurface volume of displaced material underlying soil.

y ySAGD has had a caprock breach steam release to surface.

SurfacemineableSurfacemineable

In-Situ Bitumen Thermal: Steam-Assisted Gravity Drainage (SAGD)

In siturecoverableIn siturecoverable

M 18 2006May 18, 2006, steam release

Vertically rotated bedsrotated beds Cretaceous Clearwater Formation ‘caprock’caprock(based on lithology & marine fossils)

Damage to a surface pipeline west of the release. p pThe impact was on the top and west side of the pipeline indicating the rock that did th d t h h dthe damage must have had a fairly vertical trajectory (went up and over the pipe-line and denting it on the

Map of displaced material on surface to varying degrees (including dust plume of line and denting it on the

far side of the incident event)

( g ppulverized bitumen, rock fragments and projectiles)

Pre-Release Operations

• On circulation 4 months with

pWell Pair 204-I1P1:

pressures often reaching estimated fracture pressure of 1700 kPag at well depth.

• On semi-SAGD for about oneOn semi SAGD for about one month with pressures often reaching fracture pressure. After the first two weeks there were indications of fracture/shearingindications of fracture/shearing events.

• Well pair shut in to install pump, then operated in full SAGD mode. Step wise steam rate increasesStep-wise steam rate increases while bhp increased to 1400 kPag.

May 18 2006May 18, 2006 Steam Release.

Most-Likely & Possible Steam Release Scenarios• Excessively high operating bottom hole pressure during circulationExcessively high operating bottom hole pressure during circulation and semi-SAGD, peaking at about 1800 kPag (Est. fracture pressure from mini-frac test was ~1700 kPag at well depth).

Pool of steam and water abovePool of steam and water above overburden stress grew under the shale barrier, causing the shale to heave upwards significantly, with the maximum shear strain and stress located along the shoulder of the heaved areashoulder of the heaved area

d

May 18, 2006 Steam Release

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• Not coincidental that two Abandoned Wells within 20

Most-Likely Scenario Abandoned Wells within 20 m of steam release incident (uncemented, never located).

• 3 D seismic interpretation• 3-D seismic interpretation could be a vertical fracture or a “chimney”

• Rather than a localized• Rather than a localized chimney forming during circulation period, a vertical fracture initiated on April p12, 2006. Fracture could have been associated w/ abandoned well or a pre-

i ti t l f texisting natural fracture or fault in the area.

• Argument against vertical f t i i i f t tfracture is mini-frac tests,

However …….

Area is Karst TerrainPaleohighs in Red: 265 -245 m asl; Sinkholes in Blue: 225 – 215 m asl

• The mini-frac indicated that the vertical stress was only a little lower than the minimum horizontal stress, and the test was done on a well over 1 mile west of release site.

west of release site.

• If karsting reduced the i i h i t l t

Inside karst 11.5 – 16.7 kPa/m

minimum horizontal stress below the vertical stress locally, then a vertical f t ld h d

Mini-frac test well

fracture could have occurred.

• Other Possible Contributing Localized sinkhole in Devonian

gGeologic and Wellbore Issues (See Next Slide)

Outside of karst: 21 kPa/m

Joslyn Ck SAGD Site

Well pair 204-I1P1

AB/09-33-095-12W4/0 Evaluation Well Bottomhole Location

00/09-33-095-12W4/0 Observation Well

Possible Scenario Involving Nearby Vertical Wells • Breach of caprock in close proximity to two vertical wells;AB/9-33 evaluation well abandonment shows a single-stage plug back and abandonment with no cement returns reported and no tagging of the cement top;tagging of the cement top;

• Well abandonment could have left sections of the hole without t idi th t ith th C t b dcement, providing the steam with a pathway. Cement bond over a

clean unconsolidated oil sands zone is not necessarily a seal;

• Possible scenario: horizontal fracture on April 12 moved to thePossible scenario: horizontal fracture on April 12 moved to the abandoned evaluation well AB/9-33 (the observation well appeared largely undamaged but they could not locate the uncased evaluation well);evaluation well);

• Steam then moved up through gaps or channels in the well’s cement abandonment plug until it reached the Wabiskaw C gas sand. After that, the scenario is the same as the most likely scenario.

Other Possible Contributing Geologic Factors• Glacial Tectonics

Glacial Thrust Triangle

Associated with Moraines Faulted/Folded Caprock.Glacial-Thrust Triangle Zones: Fort Hills, Fort MacKay, Cold Lake

Glacial Bedrock Channels

• Removal by Glacial Erosion of Previous Caprock by ‘BedrockCaprock by ‘Bedrock Channels.’

(from Langenberg & Hein, 2006)

• Subsidence Tectonics Other Possible Contributing Geologic Factors

Associated with Karst.LiDAR (Light Detection and Ranging) Image North of Joslyn Creek

Occ rrence of preOccurrence of pre-existing Faults/Fractures (Vertical Conduit)

• Sandy Zones within Zone Identified asZone Identified as Clearwater ‘Caprock ‘‘Shale’ is not really Shale

Photograph of core in area

y

Dominant to ImportantSalt DissolutionAthabascaGeological FactorsAthabasca Oil Sands

ImportantGlacial TectonicsContributingBedrock Tectonics

DominantKarstingDominant to ImportantSalt Dissolution

Main Lesson – You Have to Look

ImportantFaulting

ContributingCaprock integrityDominantPre-existing topographyBeyond Individual

Well Bore

ERCB Joslyn Ck Steam Release Investigation• New ERCB Requirements for Caprock Integrity and

Maximum Allowable Injection Pressures Especially in Sh ll SAGD A

ERCB Joslyn Ck Steam Release Investigation

Shallow SAGD Areas;

• Directive 51 (D51) Rewrite and revisions (ongoing);ec ve 5 ( 5 ) ew e d ev s o s (o go g);

• Regional Caprock Integrity Study (ongoing): Joint Between Alb t G l i l S (ERCB Ed t Offi ) dAlberta Geological Survey (ERCB Edmonton Office) and ERCB Calgary Office;

• Part of a Developing Program Dealing with Caprock Integrity for other Energy Development (i.e. Tight Gas, Tight Oil, CO2 Sequestration, etc. ) in Alberta., q , )

Fm integrity : Capacity of geological strata w/stand changes in thermal & stress fields.

ERCB Formation Integrity Program

Similar Strategies Re: Future CO2 InjectionSimilar Strategies Re: Future CO2 Injectiong 2 jg 2 j