Depth Imaging:Depth Imaging: Today’s Tool for Risk ReductionToday’s Tool for Risk Reduction

HighlightsHighlights

• Depth imagingDepth imaging– Reasonable timeframeReasonable timeframe– Reasonable cost Reasonable cost – Superior imagesSuperior images

– Simpler, more geologicSimpler, more geologic– Reduced exploration riskReduced exploration risk

OverviewOverview

• Differences: Time and depth migrationDifferences: Time and depth migration• PSDM: Tiered approach to depth imagingPSDM: Tiered approach to depth imaging• Resource play data exampleResource play data example• Tiered Depth-imaging summaryTiered Depth-imaging summary

Differences: Time & Depth MigrationDifferences: Time & Depth Migration

• Algorithms are fundamentally the sameAlgorithms are fundamentally the same– Traveltime surfaces are the differenceTraveltime surfaces are the difference

• Time migration: Time migration: – 2D ray tracing from image point2D ray tracing from image point

• Depth migration:Depth migration:– 3D ray tracing from acquisition geometry3D ray tracing from acquisition geometry

• Time migration:Time migration:– Velocities are less geologic and have low spatial resolutionVelocities are less geologic and have low spatial resolution– Lateral velocity variations produce mis-imagingLateral velocity variations produce mis-imaging

• Depth migration:Depth migration:– Velocities are more geologic, with higher spatial resolutionVelocities are more geologic, with higher spatial resolution– Algorithmic accuracy results in better focusing and stable Algorithmic accuracy results in better focusing and stable

phase in the dataphase in the data

Differences: Time & Depth MigrationDifferences: Time & Depth Migration

• Leverage PSTM velocitiesLeverage PSTM velocities– Global tomographic inversion (not Dix!) to generate Global tomographic inversion (not Dix!) to generate

robust depth/interval-velocity fieldrobust depth/interval-velocity field– Ensure geologic consistencyEnsure geologic consistency

• Successive decision pointsSuccessive decision points– Tier 1Tier 1: Initial depth volume: Initial depth volume

• Geologically simplerGeologically simpler– Tier 2Tier 2: Iterative tomographic updates of velocities: Iterative tomographic updates of velocities

• Establish survey-resolution velocity limitsEstablish survey-resolution velocity limits– Tier 3Tier 3: Vertical well-log registration: Vertical well-log registration

• Define anisotropic parameters for advanced imagingDefine anisotropic parameters for advanced imaging

PSDM: Tiered depth imagingPSDM: Tiered depth imaging

• Tier 1Tier 1: Initial depth volume and gathers: Initial depth volume and gathers– Decision Point:Decision Point:

• Validate PSTM volume?Validate PSTM volume?– Interpretation proceedsInterpretation proceeds

• Significant differences?Significant differences?– Prioritize to Prioritize to Tier 2Tier 2

oror– Prioritize for internal company depth imagingPrioritize for internal company depth imaging

PSDM: Tiered depth imagingPSDM: Tiered depth imaging

• Tier 2Tier 2: Iterative tomographic refinement of velocities: Iterative tomographic refinement of velocities– Gathers well behaved?Gathers well behaved?

• Establish survey-resolution velocity limitsEstablish survey-resolution velocity limits– Vertical well-log registrationVertical well-log registration

• Significant “Delta” (seismic/well depth differences)?Significant “Delta” (seismic/well depth differences)?– Move to Move to Tier 3Tier 3

• Establishing need for Establishing need for Tier 3Tier 3 reduces risk reduces risk

PSDM: Tiered depth imagingPSDM: Tiered depth imaging

• Tier 3Tier 3: Anisotropic PSDM: Anisotropic PSDM– Epsilon (moveout complexity) scans for given “Delta”Epsilon (moveout complexity) scans for given “Delta”– Continue to reduce risk…Continue to reduce risk…

PSDM: Tiered depth imagingPSDM: Tiered depth imaging

Depth Migration ValueDepth Migration Value

• Continued refinement of seismic dataContinued refinement of seismic data– Well-defined flow with intuitive decision pointsWell-defined flow with intuitive decision points

• Natural progression from time-to-depth imagingNatural progression from time-to-depth imaging– Use simple, robust tomographic solution (Use simple, robust tomographic solution (Tier 1Tier 1))

• Extract information already contained in seismic volumesExtract information already contained in seismic volumes– Not restricted to complex geology (Not restricted to complex geology (Tier 2Tier 2))

US Land Resource Play ExampleUS Land Resource Play Example

Prestack TimePrestack Time

PreStack Time Migration Image

Prestack TimePrestack Time

PreStack Time Migration Image

Tier 1 Prestack DepthTier 1 Prestack Depth

PreStack Depth Migration Image

Tier 1 SummaryTier 1 Summary

• Superior imaging to PSTMSuperior imaging to PSTM• Leverages PSTM velocitiesLeverages PSTM velocities• Necessary step prior to Necessary step prior to Tier 2Tier 2

– Tier 1Tier 1 residuals are quantitative indicator for residuals are quantitative indicator for Tier 2Tier 2• A critical risk-reduction tool for evaluating PSTMA critical risk-reduction tool for evaluating PSTM

Tier-1 PSDM GathersTier-1 PSDM Gathers

Note moveout not addressed by Tier 1 product: QC for Tier 2

Tier-1 Depth Migration Gathers

Move to Move to Tier 2Tier 2

• Tier 2 Iterative TomographyTier 2 Iterative Tomography::– Yields greater velocity resolution and a refined depth imageYields greater velocity resolution and a refined depth image– What spatial resolution can we expect from What spatial resolution can we expect from Tier 2Tier 2 Depth Depth

migration velocities?migration velocities?• The X, Y, Z improvement in resolution compared to The X, Y, Z improvement in resolution compared to Tier 1Tier 1

is approximately a factor of 10is approximately a factor of 10• Top-down layer stripping is seldom successfulTop-down layer stripping is seldom successful

– Responsible for lengthy PSDM processing timesResponsible for lengthy PSDM processing times

PSTMPSTM

PreStack Time Migration Image

Tier 1 PSDMTier 1 PSDM

Tier 1 Depth Migration Image

Tier 2 PSDM (tomo)Tier 2 PSDM (tomo)

Tier 2 Depth Migration Image

Iteration QCIteration QC

• Each iteration of migration should yield a more focused Each iteration of migration should yield a more focused and structurally simpler imageand structurally simpler image– Interpretationally intuitive Interpretationally intuitive

Tier-1 Sed Vel PSDMTier-1 Sed Vel PSDM

Tier 1 Depth Migration Gathers

Tier-2 Tomography Tier-2 Tomography

Tier 2 Depth Migration Gathers

Tier 2 SummaryTier 2 Summary

• A gridded, tomographic update yields greater resolution A gridded, tomographic update yields greater resolution and image quality than PSTM or and image quality than PSTM or Tier 1Tier 1 PSDM PSDM

• An important risk-reduction to evaluate the An important risk-reduction to evaluate the Tier 1Tier 1 product product

Tiered Depth Imaging SummaryTiered Depth Imaging Summary

• Leverage PSTM effort and workflowLeverage PSTM effort and workflow• Critically evaluate your PSTM imageCritically evaluate your PSTM image• Improved image, Improved image, reduced riskreduced risk• EconomicEconomic• Quick cycle-timeQuick cycle-time• Intuitive, interpreter-oriented quality controlIntuitive, interpreter-oriented quality control

Key Points – Again…Key Points – Again…

• Depth imagingDepth imaging– Reasonable timeframeReasonable timeframe– Reasonable cost Reasonable cost – Superior imagesSuperior images

– Simpler, more geologicSimpler, more geologic– Reduced exploration riskReduced exploration risk

• Can you afford Can you afford notnot to image in depth? to image in depth?

Presenter Contact InformationPresenter Contact Information

Russell KappiusRussell Kappius

Senior Advisor, Geophysics and DevelopmentSenior Advisor, Geophysics and Development

Sterling Seismic Services LtdSterling Seismic Services Ltd

Littleton, Colorado 80120Littleton, Colorado 80120

(303) 347-9011(303) 347-9011