Analyzing pressure responses to Earth Analyzing pressure responses to Earth tides for monitoring COtides for monitoring CO22 migration migration

Kozo SatoGeosystem EngineeringThe University of Tokyo

ObjectiveObjective Monitoring techs for geological sequestration

seismic (4D, VSP, cross-well tomography) non-seismic (electromagnetic, gravity, tilting, logging)

Alternative technique? cost-effective labor-saving

Utilize pressure responses to Earth tides perturbation by the M and the S (no artificial energy

required) pressure measurements only (no extra operation required)

OutlineOutline Objective Tidal deformations

Earth tide Cubic dilatation Calculation of Cubic dilatation

Poroelasticity Tidal signals in pressure responses Results and discussion Concluding remarks

Tidal deformationsTidal deformations Earth tide

Tidal deformation (cyclic compaction and expansion) of the solid Earth

phenomenon similar to ocean tides the gravitational attraction of the solar system bodies: M

and S

Tidal deformationsTidal deformations Cubic dilatation

cubic dilatation (trace of strain matrix)

normal stresses and strains

near the Earth surfacefree surface boundary condition 0rr

rr

iiii 2

)(22

Tidal deformationsTidal deformations Calculation of cubic dilatation

as a linear combination of Y and its derivatives w.r.t.

Y: spherical harmonics defining tidal potential

sample calculation of (an onshore site, Nagaoka, Japan)(latitude: 37.40, longitude: 138.70)

2

0

2 ),()/(m

mmYcargV

)/,,()/,,( 22 YYYY

OutlineOutline Objective Tidal deformations Poroelasticity

Deformations and pressure fluctuation and CO2 migration

Tidal signals in pressure responses Results and discussion Concluding remarks

PoroelasticityPoroelasticity

Deformations and pressure fluctuation tidal deformation induces pressure fluctuation p

Biot-Gassmann equation

poroelastic parameter

KKp

u

12

sfu KK

KK

sf KKp

1

PoroelasticityPoroelasticity

and CO2 migration Kf for the H2O-CO2 system

as a function of SCO2

sf KK

1

222

11)1(1CO

COw

COf K

SK

SK

PoroelasticityPoroelasticity

and CO2 migration Kf for the H2O-CO2 system

as a function of SCO2

KCO2=0.003~0.07GPa, Kw=2.4GPa @1000m increases as SCO2 increases: =ASCO2+B

=/p : a good indicator for monitoring the CO2 migration

BASKK

SKK

CO

swCO

wCO

2

22

111

222

11)1(1CO

COw

COf K

SK

SK

OutlineOutline Objective Tidal deformations Poroelasticity Tidal signals in pressure responses

Pressure responses Retrieving p(t) from p(t)

Results and discussion Concluding remarks

Tidal signals in pressure responsesTidal signals in pressure responses Pressure responses

long-term pressure trend pt(t) associated with a certain event, s.a. CO2 sequestration

Tidal signals in pressure responsesTidal signals in pressure responses Pressure responses

long-term pressure trend pt(t) associated with a certain event, s.a. CO2 sequestration

total pressure response p(t) : superposition of pt(t) and p(t) p(t): tidal signal induced by the Earth tide

)()()( tptptp t

Tidal signals in pressure responsesTidal signals in pressure responses Retrieving p(t) from p(t)

model the long-term pressure trend with the cubic spline

retrieve the tidal signals

n

jjjt ptNtp

1)()(

)()()( tptptp t

p(t) pt(t)

Tidal signals in pressure responsesTidal signals in pressure responses Retrieving p(t) from p(t)

model the long-term pressure trend with the cubic spline

retrieve the tidal signals

p(t) pt(t) p(t)

n

jjjt ptNtp

1)()(

)()()( tptptp t

OutlineOutline Objective Tidal deformations Poroelasticity Tidal signals in pressure responses Results and discussion

Monitoring at a sequestration test field Estimation of Detection of CO2 arrival

Concluding remarks

Results and discussionResults and discussion Monitoring at a sequestration test field

onshore aquifer, Nagaoka, Japan sandston bed, thickness: 60m, depth: 1100m injection well: CO2-1, Zone-2a (6m) and Zone-2b (6m) monitoring wells: CO2-2, CO2-3, CO2-4

CO2-4

CO2-2

CO2-3CO2-1

60m

120m

40m

loggingpressure measurements

logging

logging

Results and discussionResults and discussion Monitoring at a sequestration test field

pressure measurement time-lapse sonic logging (compressional wave velocity)

Results and discussionResults and discussion Monitoring at a sequestration test field

is it possible to detect CO2 arrival only with pressure data?

=ASCO2+B

Results and discussionResults and discussion Estimation of (132-139 days)

calculation of

Results and discussionResults and discussion Estimation of (132-139 days)

p retrieved from the pressure data

Results and discussionResults and discussion Estimation of (132-139 days)

=/p scaled to match the p profile

Results and discussionResults and discussion Estimation of (132-139 days)

=/p scaled to match the p profile 1GPa 17.0

p

Results and discussionResults and discussion Estimation of (387-394 days)

calculation of

Results and discussionResults and discussion Estimation of (387-394 days)

p retrieved from the pressure data

Results and discussionResults and discussion Estimation of (387-394 days)

=/p scaled to match the p profile

Results and discussionResults and discussion Estimation of (387-394 days)

=/p scaled to match the p profile 1GPa 40.0

p

Results and discussionResults and discussion Detection of CO2 arrival

1GPa 40.0

p

1GPa 17.0

p

Results and discussionResults and discussion Detection of CO2 arrival

time-lapse estimation (13 intervals)

Results and discussionResults and discussion Detection of CO2 arrival

time-lapse estimation (13 intervals) =ASCO2+B

Results and discussionResults and discussion Detection of CO2 arrival

time-lapse estimation (13 intervals) =ASCO2+B

Results and discussionResults and discussion Detection of CO2 arrival

time-lapse estimation (13 intervals) =ASCO2+B

OutlineOutline Objective Tidal deformations Poroelasticity Tidal signals in pressure responses Results and discussion Concluding remarks

Concluding remarksConcluding remarks The poroelastic parameter , a function of SCO2, can

be estimated from p and . The CO2 migration can be monitored with time-lapse

estimations of . The technique is applicable to well-developed sites

(depleted o/g reservoirs).