A presentation on an article "strategies in geophysics: estimation of conventional and unconventional resources". Also a catchy analogy of a story "Nimboo pani" with role of a geologist in the current energy scenario.

1. IDEAZ
New Trends in Earth Sciences -
Exploration of Energy Resources
Akhil Prabhakar (Int. Mtech 4th yr GPT)
Swapnil Pal (Int. Mtech 4th yr GT)
Ojaswita Singh (Mtech 1st yr GPT)
IIT Roorkee

2. STRATEGIES IN GEOPHYSICS FOR
ESTIMATION OF CONVENTIONALAND
UNCONVENTIONAL RESOURCES.
Why this topic?
With every passing day, energy security and availability is becoming the most
important concern for people. In this day and age, can we imagine a dignified
life and growth without access to energy?
We are fully aware of the facts that…
• Fossil fuels reserves are depleting fast. (Are they?)
• Renewables are intermittent and still expensive.
• Nuclear future seems uncertain.
• Any other breakthrough technologies don’t seem to be on the horizon yet.
Demand for energy Source of energy ?

3. Nimboo Pani
Hotel A Hotel B

4. Assumptions:
3 fresh lemons and few immature lemons
a. 1 fresh lemon = 1 glass of juice
b. Uncertainty in immature lemons

5. Hotel B
Hotel A

6. Either let the tourist go to the other
hotel as they do not have that
sophisticated technique to exploit
those immature lemons and thus
become bankrupt
Innovate in their existing
techniques to exploit those
immature lemons and meet the
present demand, thus securing their
jobs and sustaining their business.
The choice made by chef will decide the
future of Hotel A…

7. Analogy between Energy Industry and this “Nimboo Pani” story.
Hotel A
Tourist
General
Population
Oil and Gas
Industry
Geoscientist
Chef
Fresh
lemons
Conventional
hydrocarbon

8. Analogy between Energy Industry and this “Nimboo Pani” story.
Immature
lemons
Unconventional
hydrocarbon
EnergyJuice
Hotel B
Renewable
Energy

9. Innovate in their existing
techniques to exploit those
unconventional hydrocarbons and
meet the present demand, thus
securing our jobs and credibility of
being a geoscientist.
Either let the policy makers go to
the renewable energy as we do not
have that sophisticated technique to
exploit those unconventional
hydrocarbons and thus become
bankrupt
Therefore the choice made by a geoscientist will be
decisive to decide the future of Oil and Gas Industry.

10. PART I
The role of geophysics in petroleum resources estimation
and classification.
— New industry guidance and best practices
Published in “The Leading Edge, November 2012” issue.

11. Geophysical
Technologies
Uncertainty
Maturity
PRMS
Integration
of various
data sets

12. Key areas where seismic technologies impact “modern”
resource estimation:-
• Faulted Reservoirs
• Prediction of rock and fluid properties.
• Reservoir surveillance
EASY OIL is an OLD STORY… !

13. For faulted reservoirs
Seismic attributes: Used as part of integrated analysis to assess the likelihood of economically
producible reservoir in an undrilled fault block.
Seismic amplitude anomalies may be used to support reservoir and fluid continuity across faulted
reservoir provided that the following conditions are met:
• Within the drilled fault block, well logs, pressure, fluid data and test data demonstrate a strong
tie between the hydrocarbon-bearing reservoir and the seismic anomaly.
• Fault throw is less than reservoir thickness over (part of ) the hydrocarbon bearing section
across the fault and the fault is NOT considered to be a major, potentially sealing, fault.
• The seismic flat-spot or the seismic anomaly is spatially continuous and at the same depth
across the fault.
Faulted hydrocarbon-
bearing reservoir
Well logs, pressure, fluid data
Integration of data sets

14. Faulted Reservoirs…

15. Faulted Reservoirs…
A seismic amplitude anomaly has been calibrated to a hydrocarbon-bearing reservoir by well D. The
drilled area is separated by faults from three other fault blocks to be targeted by development wells
A, B, and C.
Type of resources
associated with undrilled
blocks
Hydraulic
communication
across the fault
Integrated
analysis

16. If Complex Geology…??
• Increased level of uncertainty inherent in the data
• Appropriately classify the volumes BASED ON the uncertainty components.
• The levels of risk and uncertainty should be commensurate the quality of the
data, velocity uncertainty, repeatability, and quality of supporting data.

17. Faulted Reservoirs…
Before any seismic attribute analysis, mapping the faults in 3D is a must.
This impacts the likelihood
assessment of economically
producible reservoir in
undrilled fault block, and
hence the resource
classification.
The detailed mapping of the faults PROVIDES evidence
for reservoir continuity across the fault relay-ramp,

18. Fluid Properties
• Seismic technology can be used to predict the rock and pore-fluid properties of the
reservoir and sometimes its pressure regime.
• In PRMS-AG section 3.2.2, the following guidance is given:
“The reservoir properties that 3D seismic can potentially predict under suitable
conditions are porosity, lithology, presence of gas/oil saturation as well as
pressure.”

19. An overview on seismic data quality &
requirements for such an analysis
The oil accumulation is trapped against a fault to the northeast dipping to an oil-
water contact (OWC) to the southwest. The seismic amplitude maps are from a
near-offset (left) and far-offset (right) volume. The oil-water contact appears as an
amplitude increase on the near offsets and an amplitude decrease on the far offsets.
Both run along a structural contour. The seismic amplitude response is consistent
with the trap geometry, the depositional model, and the seismic rock properties
from the well data.

20. • In this example, the key uncertainty for estimation of in-place volumes is the
distribution of net sand thickness. The low, mid, and high net sand maps are the
output of a probabilistic seismic inversion. Each map fits the well data used to
constrain the model. The three net sand maps reflect the uncertainty in the net sand
distribution and can be used to constrain three different “oil-in-place” scenarios in
low, mid and high case static models that can be carried through to reservoir
simulation and are thus key input to the resource volume assessment and
classification.
Fluid Properties…

21. Reservoir Surveillance
• Time-lapse seismology (4D seismic) impacts estimation of resources and reserves
in various ways
• Bypassed oil reserves can be spotted on time-lapse seismic when a compartment
fault block or other discrete component of the trap) is identified by time-lapse
seismic as an isolated pool that previously was believed to be part of the field’s
connected pool or pools.

22. New
discoveries
Fluid contact
surveillance
Development
of Oil
Recovery
Techniques
Reservoir
Surveillance
Better (&
time
updated)
resource
estimation

23. …Updated reservoir estimates
• Time-lapse seismic results revealed an area in the west of the F block without 4D sweep that
differed from what was expected.
• Spectrally boosted 3D seismic  evidence for a (newly mapped) normal fault cutting the F
block into two separate blocks.
• The new fault was incorporated in the model update, allowing an improved history match by
adjusting the fault seal properties.
• Now, the initially bypassed volumes block F will have to be reclassified from “developed
reserves” to “contingent resources”.
BUT…
Until further
development activities
mature!

24. …Updated reservoir estimates
• Changes of saturation in the interval swept by the water can noticeably alter the
acoustic/elastic impedance of the reservoir. This impedance change can be
detected by time-lapse seismic comparisons.
• These OWC changes, as derived from time-lapse seismic results, can subsequently
be mapped out laterally and be used to UPDATE the static and dynamic reservoir
models hat underpin the resources and reserves volumes estimate.

25. …Updated reservoir estimates
• Steam-assisted gravity drainage (SAGD) (in-situ thermal recovery method) is being used to
develop some 20 billion barrels of bitumen below the surface.
• The acoustic properties of bitumen sands  strong response to temperature changes.
a significant velocity decrease through zones in the
reservoir which have been thermally altered by the
SAGD process.
monitoring of the thermal
evolution over time.

26. Uncertainty in seismic predictions
Predictions from 3D seismic data aimed at defining
Inherent Uncertainty
Fluid flow
Rock/Fluid
properties
Trap
geometry
The accuracy of a given seismic
based prediction is dependent on:
1. The quality of the seismic data
(bandwidth, frequency
content, signal-to-noise
ratio, acquisition and processing
parameters, overburden
effects, etc.).
2. The uncertainty in the rock
and fluid properties and the
quality of the reservoir model
used to tie subsurface control to the
3D seismic volume.

27. ANSWER lies in
Integration
of data…
• It is important to realize that this
uncertainty assessment will need
to be kept evergreen and needs
to be revisited when new data
become available.
This integrated work
flow is the key to:
•Near future exploration works
in complex geologies.
•Efficient extraction of
hydrocarbons from wells.
• Exploration of
unconventional resources.

28. Unconventional resources
Conventional resources
Conventional resources exist in discrete
petroleum accumulations related to a
localized geological structural feature
and/or stratigraphic condition
(typically with each accumulation
bounded by a down-dip contact with an
aquifer) that is significantly affected by
hydrodynamic influences such as the
buoyancy of petroleum in water.
Unconventional resources
Unconventional resources exist in
hydrocarbon accumulations that are
pervasive throughout a large area and
that are generally not significantly
affected by hydrodynamic influences
(also called “continuous-type deposits”).

29. PART II
Transition from Conventional to Unconventional
Strategies in geophysics for estimation of
unconventional resources.
Published in “The Leading Edge, November 2012” issue.

30. Overview
• The rise of unconventional resource plays to prominence in the oil and gas industry
has presented geophysics with a set of unprecedented challenges, chief among
which is problem of resources and reserve estimation.
Traditional
concern
Unconventional
resource
Reservoir quality
Trap mapping

31. Parameters for reserve estimation
Conventional Petroleum
System
Chance Factors Critical Chance
Source
Charge
Trap
Reservoir
Containment
Unconventional Petroleum
System

32. Important areas which need to be
addressed
The quantification of
“deliverability system” is the
principal area which
geophysical methods must
address.
Reliance on seismic
inversion, attributes such as
curvature and coherence, and
micro-seismic data.
The low porosity of many
unconventional reservoir
demands greater trace to trace
fidelity and low noise in the
geophysical data.
Premium acquisition program
are needed, together with
strict quality assurance
standards.

33. Geophysical workflow
Defining
the
container
Establish
reservoir
continuity
Predict
reservoir
properties
Integrate
with other
data
analyses

34. Defining the container
Reservoir estimation begins by
defining the boundaries of the
reservoir unit.
Non-interpretable coal beds
are marked using isopachs and
isochrons from usable
horizons.
Shale gas reservoir can exhibit
subtle reflection character
and may not be map able for
traditional horizon picking. In
such cases, inversion volumes
must be used to define
reservoir boundaries.
It is already known
where the hc’s are!
Additional Geological
constraints are the key!

35. Establish reservoir continuity
Unconventional reservoirs can be surprisingly
heterogeneous.
Oil sands reservoirs often contain channel
system whose fill can now be non-reservoir.
Gas shales can contain non-reservoir facies
that also act as frac barriers.
These volume cannot contribute to estimates
of original gas in place (OGIP) or oil in place
(OOIP), also they can render reservoir zones
inaccessible to drainage.
All these reservoir must be identified and
mapped and their volumes subtracted from the
gross reservoir volume before a development
plan with project economics can be prepared.
Source: The leading edge, the strategies in geophysics for
estimation of unconventional resources.
Subtle nature of features being mapped
makes consistent interpretation difficult!

36. Establish reservoir continuity
The problem arises in connection with
the often low contrast nature of these
features in unconventional reservoirs
and with the subtle character expression
of lithology and mechanical
stratigraphy. Statistical approaches
can be of value.
What are the tools of geophysics
which can be used? Inversion products
such as Poisson’s ratio and young’s
modulus may be needed to characterise
geobodies; coherence
volume, character-based facies
classification, and such proprietary
techniques as Ant tracking are
useful, but they require regional
calibration. Source: The leading edge, the strategies in geophysics for
estimation of unconventional resources.

37. Predict reservoir properties
The resource play geophysics differs the most from conventional-play-geophysics. In
shale gas projects, geophysics is called upon to characterize reservoir properties
before and after the frac program.
The engineers want to know the in-place resource, the fracability, faults to
avoid, variations in principal stress direction, the location and orientation of natural
fracture systems and the location of barriers. After the frac program, the engineers want
to know the SRV, the overlap between fracture patterns, and the location or distribution
of proppant emplacement, all which are critical input for geophysical recovery factor
calculation.
Source: The leading edge, the strategies in geophysics for estimation of
unconventional resources.
Principal stress
directions and
pore pressures
are same…

38. Resource-play unconventional resource geophysics has 2
principal tasks:
Characterise the
state of the
reservoir before
complete
simulation
Evaluate the
modification of
reservoir into a
state that
permits
economic
production.
Resource play
unconventional
resource
geophysics

39. Resource-play unconventional resource geophysics has 2
principal tasks:
To characterize the state of the
reservoir before completion simulation.
• In both shale and tight oil
projects, hydrocarbon recovery is
dependent on the existence and
connectivity of natural fractures.
Often the fairway of interest for the
exploitation of such resources is
found by mapping these natural
fracture systems. In addition to define
fracture related producibility are
velocity and amplitude anisotropy
combined with shear wave
birefringence.
To evaluate the modification reservoir
into a state that permits economic
production.
• This requires us to monitor the
stimulated rock, identify bypassed
resource pay, verify the resource
confinement after stimulation, and
predict or forecast the hydrocarbon
delivery success from stimulation-
induced changes in observed
geophysical characteristics. In oil
sands work, SAGD projects require
geophysics to track the growth of
steam chambers with 4D seismic
surveys.

40. Integrate with other data analyses
• This stage in the workflow is critical for unconventional resource geophysics.
• Coherence techniques, curvature, horizontal anisotropy, and edge-detection
algorithms can predict fracture zones, but they must be compared with core and
image-log data from horizontal wells to calibrate them.
• In unconventional plays, the geophysicists at present is perceived more as a
supporting player than in traditional exploration and development, and geophysical
interpretation products and predictions sometimes encounter scepticism.
• The standards for reliability, repeatability, and accuracy are high.
• This should clearly be the future direction of R&D efforts in order for
geophysics to contribute seriously to resource and reserve estimation.

41. Data requirements, processing and analysis standards, and
emerging technologies
3D seismic acquisition, processing, and elastic
inversion
Joint P- and S-wave 3D surveys can offer
advantages
VSP surveys for unconventional reservoirs
Micro seismic data for unconventional resource
estimation
Here, the
ANSWER
lies in…!

42. Innovate in their existing
techniques to exploit those
unconventional hydrocarbons and
meet the present demand, thus
securing our jobs and credibility of
being a geoscientist.
Either let the policy makers go to
the renewable energy as we do not
have that sophisticated technique to
exploit those unconventional
hydrocarbons and thus become
bankrupt

43. “The MORE we get to know, and
the MORE we try to quantify (nature’s complexities),
the MORE we realize,
We know Less!”

44. THANK YOU
QUESTIONS…??