Lecture 14

FWS 2005 L14 – Prospect AnalysisCourtesy of ExxonMobil

Lecture 14Lecture 14

Alpha

Beta


Objectives & Relevance

• Relevance:Demonstrate some the tasks that go into

determining the size of the ‘prize’ and the risk associated with a prospect

• Objective:Introduce the types of considerations

necessary to get a prospect ready for management approval


Overview of Prospect Analysis

Given the geologic framework and the results of our data analysis, our next task is to analyze and assess viable prospects:

• Analyze prospect elements• Source, Migration, Reservoir, Trap, Seal

• Consider the most-likely scenario

• Consider other cases - the range of possibilities

• Assess the prospect• What volumes of HCs can we expect?

• Will it be oil or gas?

• Risk the Prospect

• What is our level of confidence that all the prospect elements work?


Outline

1. Define prospect elements

2. Estimating trap volume

3. HC Type

4. Assessment

5. Risk

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Outline


2. Estimating trap volume

3. HC Type

4. Assessment

5. Risk

A “Kitchen”Where Organic

Material Is Cooked

A “Container” From Which Oil & Gas Can Be

Produced

“Plumbing” To Connectthe Container to the Kitchen

CorrectlyPlacedWells


A Real HC System

Brent Sandstoneacts as a reservoir

Unconformity

Heather ShaleSognefjord Shale

both organic poor

FaciesChange

Draupne Shaleorganic rich

serves as a source rock

Gas Generation

Gas Generation

Oil Generation

Oil Generation

Immature

Immature

Immature

Immature

HC Generation & Expulsionoil & gas from the Draupne, gas from coals in the BrentHC Migrationinto Brent carrier beds and up faults

HC Fill & Spill

FaultLeakPoint

OilSpillPoint

late gas displaces early oil


Alpha Beta

Reservoir

Seal

Source

Basement

Overburden

18 Ma

Most-Likely Scenario

OilGeneration

OilMigration

OilFill & Spill

Sea Water


Alpha Beta

Reservoir

Seal

Source

Basement

Overburden

10 Ma


OilGeneration

OilMigration

OilMigration

Sea Water



Reservoir

Seal

Source

Basement

Overburden

Present

Alpha Beta

OilGeneration

GasGeneration

Oil & GasMigration

OilMigration

Sea Water



Map of the Reservoir Unit

Alpha Beta

Oil

Oil

18 Ma




BetaAlpha

OilOil

10 Ma



Alpha Beta

Oil Oil

Gas


Present


Exploration’s Task

To EMDCor EMPC

DropArea

Drill Wildcats

ConfirmationWell

Identify Opportunities

ProcessSeismic Data

CapturePrime Areas

InterpretSeismic Data

AcquireSeismic Data

AssessProspects

Success

Success

Failure

Uneconomic1. Volume2. HC Type3. Assessment4. Risk


Outline


2. Estimating trap volumes

3. HC Type

4. Assessment

5. Risk

Let’s start an exercise


Exercise 12 – Parts 1 - 6

We will do some quick estimates using a series of simplifying

assumptions


How can we get a rough estimate of the cross-sectional area?

Base 1

Height 1

Consider This ….

Let’s say our trap in cross-section view looks like this….

Base 2

Height 2


From Area to Volume

Volume of a Cone = 1/3 Π r2 * h

Consider the trap to be approximately ½ a cone

Alpha

Beta

r

h

r r


Outline



3. HC Type

4. Assessment

5. Risk

• DHI Analysis• AVO Analysis• HC Systems Analysis


Oil or Gas???

• Should there be a difference in seismic response (AVO) between an oil-filled reservoir and a gas-filled reservoir?– Model response with different rock & fluid

properties

• If there should be a difference, which fluid type does the seismic data support?– Extract amplitudes from near- and far-angle

stacks

• From our basin modeling & HC systems analysis, which fluid type should we expect– What did the source generate– What did the trap leak or spill

Qu

an

titativ

eQ

ualita

tive


Model Seismic Responses - Input

10% Porosity

Gas

Oil

Brine

20% Porosity

30% Porosity


Model Seismic Responses - Output

10% Porosity10% Porosity

OffsetOffset OffsetOffsetOffsetOffset30% Porosity30% Porosity20% Porosity20% Porosity


Model Seismic Responses - Output

-0.4

-0.2

0.0

0.2

0.4

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

Intercept

Slo

pe

GasOilBrineShale

10%

20%

30%

AVO Crossplot


Questions???

• How can we verify this scenario?

• To what level are the traps filled with oil & gas?

• What would be the value ($) if our scenario is correct?

• How much more/less HC could there be?

• How risky is this prospect (chance that we are totally wrong)?

Many times the seismic data will give us clues!

Many times the seismic data will give us clues!


Seismic Line Across ‘Alpha’

Fluid Contact?Oil over Water?

Fluid Contact?Gas over Oil?

Alpha


Outline



3. HC Type

4. Assessment

5. Risk


Types of Assessments

• Deterministic Assessment– One value for each parameter– One final number, e.g., 200 MBO

• Probabilistic Assessment– A range of values for each parameter– A range of outcomes, e.g. 200 ± 50

MBO

Once a lead has been high-graded into a prospect, we have to assess its potential value


Scenarios & Probabilities

Gas Cap & Oil Leg

Alpha

40% Chance of Occurrence

Scenario 3

Scenario 1 Scenario 2

Scenario 4Alpha

Alpha

Alpha

Gas Only

Oil Only Low Gas Saturation

30% Chance of Occurrence 10% Chance of Occurrence

20% Chance of Occurrence


ESTIMATES Alpha Beta

1. Gross Rock Volume

2.91 km3

2.12 km3

2. Reservoir Volume

1.02 km3

0.66 km3

3. Pore Volume

0.25 km3

0.15 km3

4. In-Place Volume

0.20 km3

0.12 km3

5. In-Place – Barrels

1280 MBO

735 MBO

6. EUR – Unrisked

288 MBO

132 MBO

7. EUR – Risked

MBO

MBO

Deterministic Prospect Assessment

To Assess a Prospect, We Assign Numbers to the Parameters related to HC Volumes

In our exercise, we have assumed the all oil case (Scenario 3)

Unrisked means everything in the HC System has worked!


Alpha Prospect Assessment Results

0 MOEB0 GCF0 MBOScenario 4Low Gas Saturation

288 MOEB0 GCF288 MBOScenario 3Oil Only

86 MOEB515 GCF0 MBOScenario 2Gas Only

178 MOEB97 GCF162 MBOScenario 1Oil & Gas

Oil Gas Oil-Equivalent

Assuming 100 MOEB is needed to make prospect economic

Uneconomic

Million Barrels Oil Billion Cubic Ft Gas Million Oil Equivalent Barrels

6 GCF = 1 MBO

Uneconomic


Probabilistic Assessment

• The Goal is to Get A Number and a Range of Possible Outcomes

• We Input a Range of Values for Each Assessment Parameter – usually minimum, most-likely, maximum

Area

2012 27

MLMin Max

HC Sat.

Thickness Net:Gross Porosity

FVF Recovery


Unrisked Results

Million Barrels of Oil

Alpha Prospect – Unrisked

0%

20%

40%

60%

80%

100%

0 100 200 300 400

100

Econ

om

ic M

inim

um

50% Chance of finding 200 MBO or more75% Chance of finding the economic minimum

Exc

edan

ce P

rob

abil

ity


Outline



3. HC Type

4. Assessment

5. Risk

75% Chance of Success

25% Risk


9 Key Elements of the HC System

Biodegra-dation

Not Low Gas Saturation

HC Migration

Source Maturation

Source Quality

Trap Quality

Seal Adequacy

Reservoir Quality

Reservoir Presence

• A team of experts consider these key elements for each prospect.

• They rate the chance of success (COS) for each on a scale of 0 to 1


COS for Alpha

• Alpha’s biggest risk is that the fault does not seal.

• There is also some risk that the trap holds low gas saturation and that reservoir quality is poor• Reservoir Presence

• Reservoir Quality

• Trap Quality

• Seal Adequacy

• Source Quality

• Source Maturation

• HC Migration

• Not Low Gas Saturation

• Biodegradation

- - - - 1.0

- - - - 0.85

- - - - 1.0

- - - - 0.8

- - - - 1.0

- - - - 1.0

- - - - 1.0

- 0.9

- - - - 1.0

}0.61

chance of success

(COS)

Some Risk

Highest Risk

Some Risk


Risked Probabilistic Assessment Results

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400 500

Million Oil Equivalent Barrels

Alpha Prospect – Main Compartment - Risked

Gas Cap & Oil Leg

Gas Only 61 % COS

51 % Chance of Finding More

Than theEconomicMinimum

72% Chance to find any hydrocarbons58% Chance to find 100 MBOE 5% Chance to find 400 MBOE

100

Oil Only

Econ

om

ic M

inim

um


Exercise 14 – Part 7

In the exercise we will use • A COS of 61%• An economic minimum of 100

MBOE

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Lecture 14

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