MANCHESTER 1824

Seismic geomechanics of mud volcanoes –

Implications for drilling

Rashad Gulmammadov

Stephen Covey-Crump

Mads Huuse

MINISTRY OF EDUCATION REPUBLIC OF AZERBAIJAN

Study funded by

MANCHESTER 1824 Outline

Rationale

Overview of mud volcano case study

Feasibility calculations

2D model

Overpressure

Fluid flow

Stress regime

Drilling window

MANCHESTER 1824 Rationale

Active tectonics Rapid

sedimentation High rate of gas

generation

Mud volcano

Shallow earthquakes Gryphons & pockmarks

Lateral stress perturbations

Fractures

Mud flow/breccia hazard

Island/submarine banks

Sediment instability/landslide

Hydrate hazard

Gas emission/flame hazard

MANCHESTER 1824 Rationale

But how does the geomechanics of

mud volcanoes come into play?

MANCHESTER 1824 Why MV geomechanics?

Analytical models of

rock properties

Mud volcano growth/deformation

history

Pressure and fluid distribution

Stress state analysis

Fault and fracture quantification

FORMULATING DRILLING

STRATEGIES

MANCHESTER 1824 Study area

Azeri-Chirag-Guneshly (ACG) – a field complex within anticlinal structures in northern SCB

Water depths of 95-425m

Mobile shales from the organic rich Maykop sequence

MANCHESTER 1824 Review of the Chirag mud volcano

Geometric parameters & activity: WD – water depth, SD – surface diameter, HPE – highest point

elevation, MCT - mud cone thickness, MCV – mud cone volume, LEV – last eruption volume

Overburden: IOD – IT – illitization temperature, illitization onset depth

Sediment source: SSTD – sediment-source top depth, TH – thickness

Others: Poro – porosity, Perm – permeability, GG – geothermal gradient, PPG – pore-pressure gradient

IOD=4.8 km

IT=75-150 °C

WD=0.12 km

MCT=1.4 km MCV=22.5 km3

LEV=2.7 km3

HPE=15 m

Ge

om

etr

ic

pa

ram

ete

rs &

activity

SD=11 km

SSTD=5 km

Ove

rbu

rde

n

TH=1 km Poro=20 %

Se

dim

en

t

so

urc

e Poro=11 %

Perm=1 nD

Perm=0.1 nD

PPG=17.5 Mpa/km

PPG=19.5 Mpa/km

GG=12.5 °C/km

GG=21 °C/km

MANCHESTER 1824 Feasibility calculations

Vertical seismic section of an investigated mud volcano from the KAD structure in

the offshore western SCB (modified from Soto et al. 2011)

* Flank = 1500m

* Structural crest = 500m

MANCHESTER 1824 Feasibility input parameters

Generic P- and S-wave

velocities vs. depth curves in

marine sediments (modified

from Hamilton 1979)

Shale compaction curve in

northwest SCB (modified

from Bredehoeft et al. 1988)

MANCHESTER 1824 Feasibility results

Good consistency with published values

Empirical correlations are not significantly affected by local factors specific to the SCB

Values we estimated Estimated parameters Structural position Values from the literature

Type Name Unit Crest Flank Range Reference E

lasti

c p

rop

ert

ies

Bulk density kg/m3 2140 2243 1580 – 2600 Mavko et al. 2009, p. 458, 459

Shear modulus GPa 0.87 2.60 0.2-5.5 Horsrud 2001, p. 71

Lamé’s constant GPa 8.69 15.06 0.07-13.26 Islam & Skalle 2013, p. 1400

Poisson’s ratio - 0.44 0.40 0.35-0.50 Schön 2011, p 162

Young’s modulus GPa 2.52 7.25 3.2 – 9.5 Prasad et al. 2012, p. 3

Bulk modulus GPa 7.53 11.59 6 – 12 Vanorio et al. 2003, p. 325

Str

es

s a

nd

pre

ssu

res

Vertical stress MPa 13 35 10-35 Buryakovsky et al. 2001, p. 402

Horizontal stress MPa 8 22

Hydrostatic pressure MPa 5 15 4-14 Buryakovsky et al. 2001, p. 402

Pore fluid pressure MPa 6 16 12 – 20 Buryakovsky et al. 2001, p. 152

Fracture pressure MPa 11.57 28.41

Ro

ck s

tren

gth

Friction angle ° 19.67 26.30 21.75 – 38.09 Kohli & Zoback 2013, p. 5115

Cohesive strength MPa 3.58 4.94 0.3 – 38.4 Schön 2011, p. 256

UCS MPa 8.35 16.05 7.5 – 13.9 Schön 2011, p. 258

Critical shear stress MPa 7.11 17.52

Published values Estimated parameters Structural position Values from the literature

Type Name Unit Crest Flank Range Reference

Ela

sti

c p

rop

ert

ies

Bulk density kg/m3 2140 2243 1580 – 2600 Mavko et al. 2009, p. 458, 459

Shear modulus GPa 0.87 2.60 0.2-5.5 Horsrud 2001, p. 71

Lamé’s constant GPa 8.69 15.06 0.07-13.26 Islam & Skalle 2013, p. 1400

Poisson’s ratio - 0.44 0.40 0.35-0.50 Schön 2011, p 162

Young’s modulus GPa 2.52 7.25 3.2 – 9.5 Prasad et al. 2012, p. 3

Bulk modulus GPa 7.53 11.59 6 – 12 Vanorio et al. 2003, p. 325

Str

es

s a

nd

pre

ssu

res

Vertical stress MPa 13 35 10-35 Buryakovsky et al. 2001, p. 402

Horizontal stress MPa 8 22

Hydrostatic pressure MPa 5 15 4-14 Buryakovsky et al. 2001, p. 402

Pore fluid pressure MPa 6 16 12 – 20 Buryakovsky et al. 2001, p. 152

Fracture pressure MPa 11.57 28.41

Ro

ck s

tren

gth

Friction angle ° 19.67 26.30 21.75 – 38.09 Kohli & Zoback 2013, p. 5115

Cohesive strength MPa 3.58 4.94 0.3 – 38.4 Schön 2011, p. 256

UCS MPa 8.35 16.05 7.5 – 13.9 Schön 2011, p. 258

Critical shear stress MPa 7.11 17.52

MANCHESTER 1824 2D model input

Full Waveform Inversion image at

the ACG structure published by

Selwood et al. (2013)

Digitization workflow

1400 m/s 3900 m/s

TTI FWI

MANCHESTER 1824 Digitized FWI

P-wave velocity image generated from the Full Waveform Inversion image at the

ACG structure published by Selwood et al. (2013)

MANCHESTER 1824 Elastic rock properties

Profiles of elastic rock properties and acoustic wave velocities along the RM-1 pseudo-well

Markers indicate the magnitudes of these properties obtained on the structural crest of the

KAD mud volcano that was analysed in the feasibility calculations

MANCHESTER 1824 Overpressure detection

Top of pressure transition

(TPT) zone 620m

Base of pressure transition

(BPT) zone 2600m

Theoretical Inferred

MANCHESTER 1824 Fluid flow

~1.2

~1.5

~1.8

Variation of overpressure informing about the fluid flow direction near the mud volcano

Possibility of using P-wave data to assess fluid flow pathways within the stratigraphy

TPT

BPT

MANCHESTER 1824

Modified from

Hill et al. (2015)

Contemporary state of stress

MANCHESTER 1824 Contemporary state of stress

Depth, m 𝝈𝒗, MPa/m 𝑷𝒑, MPa/m 𝝁 𝝈𝑯, MPa/m 𝝈𝒉, MPa/m

620 0.0235 0.0123 0.3718 0.0356 0.0177 2600 0.0236 0.0174 0.5957 0.0369 0.0194 5000 0.0238 0.0200 0.6445 0.0328 0.0211

MANCHESTER 1824 Drilling window

TPT 620m

BPT 2600m

Variation of pressure gradients along the

pseudo-well RM-1

Vertical cross-section

across the ACG

showing the width of

the drilling window

MANCHESTER 1824 Conclusions

Geomechanical modelling based on published data allows:

realistic values for sediment properties and fluid pressures to

be estimated

spatial variations in pore pressure and prediction of overall

fluid flow vectors to be visualized

drillability assessment to support future drilling operations

MANCHESTER 1824 References

Buryakovsky, L. a., Chilingar, G. V. & Aminzadeh, F. 2001. Petroleum Geology of the South Caspian Basin, 1st ed. Elsevier, doi:

10.1016/B978-088415342-9/50000-X.

Bredehoeft, J.D., Djevanshir, R.D. & Belitz, K.R. 1988. Lateral fluid flow in a compacting sand-shale sequence: South Caspian

Basin. AAPG Bulletin, 72, 416–424, doi: 10.1306/703C9A1E-1707-11D7-8645000102C1865D.

Hamilton, E.L. 1979. Vp/Vs & Poisson’s ratios in marine sediments and rocks. Acoustical Society of America, 66, 1093–1101,

doi: 10.1121/1.383344.

Hill, A.W., Hampson, K.M., Hill, A.J., Golightly, C., Wood, G.A., Sweeney, M. & Smith, M.M. 2015. ACG field geohazards

management: Unwinding the past, securing the future. Offshore Technology Conference, OTC-25870, 1–22, doi: 10.4043/25870-

MS.

Horsrud, P. 2001. Estimating mechanical properties of shale from empirical correlations. SPE Drilling & Completion, 16, 68–73,

doi: 10.2118/56017-PA.

Islam, M.A. & Skalle, P. 2013. An experimental investigation of shale mechanical properties through drained and undrained test

mechanisms. Rock Mechanics and Rock Engineering, 46, 1391–1413, doi: 10.1007/s00603-013-0377-8.

Kohli, A.H. & Zoback, M.D. 2013. Frictional properties of shale reservoir rocks. Journal of Geophysical Research: Solid Earth,

118, 5109–5125, doi: 10.1002/jgrb.50346.

Mavko, G., Mukerji, T. & Dvorkin, J. 2009. The Rock Physics Handbook - Tools for Seismic Analysis of Porous Media, 2nd ed.

Cambridge University Press.

Prasad, M. 2002. Measurement of Young’s modulus of clay minerals using atomic force acoustic microscopy. Geophysical

Research Letters, 29, 2–5, doi: 10.1029/2001GL014054

Schön, J. 2011. Physical Properties of Rocks: A Workbook. Elsevier.

Soto, J.I., Santos-Betancor, I., Sanchez Borrego, I. & Macellari, C.E. 2011. Shale diapirism and associated folding history in the

South Caspian Basin (Offshore Azerbaijan). AAPG Annual Convention and Exhibition, 30162.

Vanorio, T., Prasad, M. & Nur, A. 2003. Elastic properties of dry clay mineral aggregates, suspensions and sandstones.

Geophysical Journal International, 155, 319–326, doi: 10.1046/j.1365-246X.2003.02046.x.