4D%20Seismic%20tools%20for%20monitoring

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4D Seismic tools for monitoring eor by carbon
dioxide sequestration
Prof. V.P. Dimri Lorenz Lecturer (AGU)
National Geophysical Research Institute, Hyderabad
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Outline of the lecture

• Need for EOR
• CO2 sequestration
• Possible potential CO2 traps
• 4D Monitoring and EOR
• Conclusions

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Need for EOR

• In India only about 27 of the oil in-place is
  being produced economically. Recovering these
  remaining oil and gas resources poses formidable
  technical and financial challenges.
• To wring even the last drop of oil economically
  from reservoir, lot of research work is going on
  for enhanced oil recovery (EOR) so that premature
  abandonment of wells can be checked.

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CO2 sequestration

• Geological sequestration of carbon dioxide is a
  means of its injection in a suitable geological
  formation.
• Typically below 1 km depth where temperature and
  pressure are above the critical point for carbon
  dioxide (31.60C, 7.38MPa).

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Geological CO2 sequestration
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Characteristics of favourable trapsfor CO2
sequestration
Geological reservoirs for safe and long storage
for carbon dioxide must meet certain criteria.
Some favourable geological traps based on
reservoir characteristics such as porosity,
permeability, and their affinity for the chemical
reactions are discussed below
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1. Perfect sealing so as to preserve it for long
   geological time, leakage could lead to
   environmental disaster
2. Suitable porosity, permeability and presence of
   suitable reactants like brine, are some of the
   criteria of good sequestration sites.

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Possible potential CO2 traps

• There could be several possible traps for
  efficient CO2 storage, few known traps are
  discussed here
• Abandoned hydrocarbon reservoirs
• Mature (Brown) oil fields
• Non-economic coal seams
• Shale formations
• Basalt formations

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1. Abandoned hydrocarbon reservoirs

1. These are the geological settings in which
   oil/gas was trapped for long geological time.
2. These abandoned reservoirs are the best possible
   locales vacated by the natural oil and gas where
   carbon dioxide can be stored.

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3. These reservoirs have proven capacity of
holding natural oil and gas and have good
sealing. 4. Under high pressure carbon dioxide
turns into liquid (super critical carbon
dioxide) and when injected in the reservoir it is
trapped below an aquiclude or seal (cap rock).
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2. Brown Oil Field Enhanced Oil Recovery

• In a brown field sequestering carbon dioxide
  becomes an additional advantage because it helps
  in enhanced oil/gas recovery.
• The injected carbon dioxide dissolves in the oil
  and reduces its viscosity. This is indeed one of
  the best known commercially viable methods to
  enhance the secondary recovery from the oil
  fields.

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Carbon dioxide injection for Enhanced Oil
Recovery
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4D Monitoring

• Monitoring of sequestered carbon dioxide is key
  concern to assure the inhabitants and to policy
  makers that it has no disastrous / adverse effect
  on the environment. Monitoring will also
  demonstrate success/failure of sequestration.
• Sequestration can be better planned by monitoring
  the carbon dioxide storage by finding those
  pockets of the reservoir which are yet to be
  flooded with the carbon dioxide.

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Indian Case study Monitoring of thermal front in
Balol oil field
There is no case study available for any Indian
oil field with CO2 injection however, thermal
recovery technique (in-situ combustion) similar
to CO2 injection, has been successfully
attempted.
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• A pilot study to monitor the thermal front caused
  by insitu-combustion in Balol heavy oil field,
  Cambay basin, was conducted.
• Time lapse (4D)seismic data was used for
  monitoring of the thermal front movement.
• Three sets of 3D seismic data acquired in 1 year
  interval were analyzed.

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Case Study
Balol oil field lies in the heavy oil belt in the
north-western part of the Cambay Basin, India
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• The reservoir zone is 32 m in thickness and top
  of the reservoir is at depth of 996 m and bottom
  of the reservoir lies at 1029 m depth. The
  porosity of reservoir is in the range of 28-30
  and its permeability varies from 8-15 darcy.
• At reservoir temperature of 72oC and pressure of
  104 kg/cm2, the viscosity of oil varies from
  100-450 Centipose and its gravity is about 15.5o
  API (Heavy Oil).
• The primary recovery of viscous and heavy oil
  from Balol is only 10-12, hence the pay zone is
  under thermal EOR process (Insitu Combustion).

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Insitu Combustion Process
Producer
Injector
air/water
Burning Front
Oil Bank
light oil
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PSTM Stack
B
M1
M2
Full stack section of migrated data along inline
633 for base (top), monitor 1 (middle) and
monitor 2 (bottom).
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B
Base Monitor1 (Before 4D analysis)
M1
Diff
B
Base Monitor1 (After4D analysis)
M1
Diff
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B
Base Monitor2 (Before 4D analysis)
M2
Diff
B
Base Monitor2 (After4D analysis)
M2
Diff
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Thermal front movement near injectors (approx.
50m / year radially). Yellowish colour near
injectors shows anomalous regions, which
represents thermal front movement.
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Inversion results
Constant time slices of inverted P-impedance are
in a 10 ms window centered at 900ms for baseline,
monitor1 and monitor2 surveys.
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• We see a drop in impedance from baseline to first
  monitor survey near all the injectors. Low
  impedance anomalies near the injector wells 145,
  147, 153 and 162 are identifiable in these
  figures and are indicative of the effect of
  combustion.

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Conclusions

• Carbon dioxide injection serves two purposes, one
  to reduce CO2 from atmosphere and other to
  enhance oil recovery from brown oil fields.
• Geological sequestration of carbon dioxide to
  reduce global warming is an active area of
  research.
• NGRI has taken a lead role to launch a project on
  Deccan Volcanic Province with financial support
  of DST, Govt. of India, as a pilot project.

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Thank You