Ensuring integrity of shale gas wells in Europe

M. Torsæter, K. Gawel, J. Todorovic, A. Stroisz, R. Skorpa and A. Lavrov

SINTEF Petroleum Research, Trondheim, Norway

M4Shale Gas Final Conference, Krakow, Poland – 19.10.2017

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Wells are most probable leakage paths!

Well integrity closely correlated to public

acceptance!

Well integrity: From drilling to plugging

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Drilling Cementing Operations Plugging

Ensuring integrity of shale gas wells in Europe

Well integrity: From drilling to plugging

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Drilling Cementing Operations Plugging

Ensuring integrity of shale gas wells in Europe

Documented:

• Borehole instability

• Poor hole cleaning,

strong torque & drag on

pipe, packoffs, bit balling,

low rates of penetration,

casing placement probs.

• Gas influx during drilling

• Lost circulation,

formation fracturing

higher up in hole (last

casing point)

PRD: Methods for better understanding in-situconditions (including 3D mapping of fractures)

Unavoidablegeological issues:Natural fractures

Elevated pore pressuresSharp pressure changes

Laminated rockReactive clays

Shale drilling hazards

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Pressure

De

pth

Stuck pipe, gas influx

Lost circulation, fracturing

Narrowmudweight

windows

Use oil-based mud, perform thorough

characterization of bothreservoir and overburden

Well integrity: From drilling to plugging

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Drilling Cementing Operations Plugging

Ensuring integrity of shale gas wells in Europe

Shale cementing problems

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Documented:

• Naturally fractured

laminated rock

(anisotropic stresses)

• Loss of cement

• Boreholes are rarely

circular (breakouts)

• Poor mud displacement

• Reactive clays: Casing

cemented off bottom

• High pore pressures: Gas

migration through

cement during setting

PRD: Develop log/method that can verify cement barrier sealing ability.

Use centralizers, tailorcement/mud/spacer

properties, log frequently.

Well integrity: From drilling to plugging

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Drilling Cementing Operations Plugging

Ensuring integrity of shale gas wells in Europe

Shale well operational damage

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Documented:

• Pipe corrosion/erosion.

• Sustained casing pressure

due to mechanical damage

to cement after setting.

• Casing diameter changes

• Formation motion

• Casing deformation (well

intersects plane on which

displacement is induced

during production:

weakness, fracture, fault)

PRD: Enable continuous non-invasive well integrity monitoring

Tailor barrier materials, continuously monitor

sustained casing pressure

Well integrity: From drilling to plugging

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Drilling Cementing Operations Plugging

Ensuring integrity of shale gas wells in Europe

Shale well long-term safety

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Documented:

• Degradation of well

barrier materials.

• Poor quality of plugs.

• Methane leakage to

surface.

• Global differences in

plugging standards.

It is still unknown how

leakage rate development

varies with time.

Reference 521 m

522 m 523 m

Pores Contamination Cement

Cement from well plug placed in 2013, cored in 2015

K.Gawel et al., Study of materials retrieved from a Ketzin CO2 monitoring

well, Energy Procedia (2017)

Microscopy study of pipes

Inside casing Outside casing

Inside tubing Outside tubing

tubing

casing

PRD: Ways to assess and remediate plugged wells

Find out what works: Perform leakage

monitoring at well siteafter plugging.

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Prediction of problems in Europe

Well Integrity predictions for European shales

Ensuring integrity of shale gas wells in Europe13

• Borehole instability• Lost circulation during drilling/cementing• Bit balling, poor hole cleaning and

packoffs due to high clay content• Cement integrity problems due to high

temperatures and great depth

Upper Ordovician & Silurian shales in the Baltic-

Podlasie-Lublin Basin

Haynesville

Marcellus

• Shallow gas influx during drilling• Poor performance of water-base mud.• Problems getting casing to bottom.• Incomplete cementing• Influxes and lost circulation in shale.• Poor hole cleaning.• Sustained casing pressure.

Bowland shale Barnett

HaynesvilleWeald/Wessex Basin

Midland Valley

General recommendations

• General: Data sharing is necessary, we needopenness about successes and failures in the field.

• Know the subsurface: Thorough characterizationof not only reservoir – but also overburden.

• Do it right the first time: Implement best drilling practices. Think about the whole well life cyclewhen chosing fluids and materials.

• Always try to improve: We suggest severalPrioritized Research Directions (PRDs) for improving well integrity in shale gas wells.

Ensuring integrity of shale gas wells in Europe14

Ensuring integrity of shale gas wells in Europe15

Thank You For Your Attention!

Contact:Malin Torsæter, SINTEF Petroleum ResearchMalin.torsater@sintef.no