Prospect Generation and Maturation

By : Frank Sinartio

Introduction

The purpose of this short summary is to give a guideline for prospect generation & maturation, starting from well data, seismic interpretation, structural and stratigraphic mapping, reservoir mapping, and fluid distribution mapping.

The emphases is on seismic and well data, but seismic processing & acquisition, petrophysics and rock physics are not included, neither is basin modeling.

Work flow and time table can be generated using this list. The example of time table included here is divided in the percentage of the time, not the amount of time. The main reason of this is that different case may have different challenges and different time frame.

Lists of other special processes/analyses, and interpretations are listed but not discussed. This is not an exhaustive lists, so the lists should always be revised.

This summary is only a guide line and not a complete check list. The summary should be revised from time to time to accommodate new technologies or processes that have not been included here. This summary can be easier to understand, if pictures of examples are included. This effort is being done.

Usage of journal book of observations is highly encouraged to take note of problems, interesting observations and alternative interpretations.

Last but not least, in the last section there is a suggestion of method to do seismic interpretation fast with good quality and a suggestion to make the seismic interpretation easier. It is named : “the fast five and the easy sixth”.

Summary of processes

1. Data Preparation and QC

• Check survey location of seismic
• Check locations of wells
• Check volume type of the seismic
• Check polarity of the seismic
• Check seismic ties between surveys
• Check quality and completeness of well curves
• Scan seismic for disturbance like multiple, pull up effect, push down effect, fault shadows etc.
• Scan the seismic for DHI: bright spot, flat spot, phase reversal

2. Journal

Write a journal complete with time about:

• Daily activities
• Misties (solved and unsolved)
• Unfinish/unsure correlation across faults
• Interesting observation: DHI, noise, recognized pattern, and any un-identified feature/pattern.

3. Well to Seismic Tie

• Sonic log and density examination/preparation
• Checkshot correction
• Wavelet Extraction
• Synthetic seismogram
• Vertical Seismic Profiling (VSP)

4. Well to Well Correlation

• Well only
  1. Structural cross section
  2. Stratigraphic cross section
• Well and seismic
  1. Seismic with wells posted (seiswork)
  2. Wells with seismic backdrop (stratwork)

5. Fault Interpretation

• Cross section view
  1. Use dip direction of the faults
  2. Avoid strike direction of fault if possible
  3. Interpret the fault on one direction only unless there is a fault that has strike direction parallel or semi parallel to the cross section view
  4. Check for consistency of the fault intersection on strike line
  5. Check for consistency and interpret fault if necessary on time-slice.
  6. Observe and recognize: growth faults, strike slip faults, and re-activated faults.
  7. Use edge detection cubes (such as coherency cube) to help visibility of fault cut.
  8. Use phase response to help visibility of fault cut.
  9. Computer automatic picking of fault cut/plane
• Time slice view
  1. Q.C. fault interpretation consistency
  2. Assign name to the faults
  3. Pick fault in several time slices to control the fault picks in cross section view
  4. Use edge detection cube (such as coherency cube) to help visibility of fault cut
  5. Use phase response to help visibility of fault cut.
• Three dimension view
  1. To show and Q.C. fault cuts and fault plane

6. Horizons Interpretation

• Cross section view
  1. First interpret horizons that is widely spread out geologically (SB & MFS), then interpret other horizons
  2. Choose one or two of the most prominent SB or MFS as hooked horizons.
  3. First use manual pick and snap it.
  4. Loop tie interpretation
  5. Reflectors in the strike lines(cross lines) will be likely more continuous than in the dip lines
  6. Start with sparse interpretation (in 3D), then increase the density
  7. Crossing fault interpretation:
  • cut & move correlation,
  • fault restoration,
  • horizon flattening
  • thickness consistency check
  • Thinning and widening check
  • Recognize the growth fault, strike slip faults, and re-activated faults
  8. Tidy up interpretation near the fault
  9. Filter the data with high cut filter to enhance visibility of lower frequency data, like Basement or deeper horizons
  10. Recognize structural closure, DHI,
  11. Computer automatic picking

• Time slice view
  1. To Q.C. horizons interpretation consistency
• Three dimension view (Volume interpretation)
  1. Usage of more than one cube at the same time.
  2. Colors & opacity
  3. Blending of colors
  4. Computer automatic picking
  5. Volume sculpturing
  6. Geobody extraction
  7. Three dimensional view of horizons, faults and geobodies
  8. Volume calculation

7. Fault Polygon Generation

• Post fault heaves
• Identify and interpret the main fault
• Honor the heaves data
• Put sign, up, down and lateral movement accordingly
• Observe and identify faults trends
• Observe and identify faults truncation. They might be truncated on a fault that was not seen in the seismic interpretation.

8. Structural Mapping

• Fault polygon completed
• Contouring
• Label, bold and hachure on the contour
• Up and down of contours on either side of the faults
• Contouring hanging wall and foot wall of reverse fault if needed.
• Colour filled contour
• Identify structural closure if any
• Structural attributes of maps (dip & azimuth)
• Isochron maps
• Palinspastic maps
• Migration pathway maps

9. Stratigraphical and Sedimentological Mapping

• Seismic attributes
  1. Instantenous attributes
  2. Horizons slice and window attributes
  3. Statistical attributes
  4. Hybrid attributes (stratimagic: pattern recognition and classification, etc)
  5. Normalization using RMS
  6. Image processing: second derivative, edge detection enhancement.
  7. Multi attribute analysis
  8. Seismic geomorphology
• Spectral balancing (amplitude and frequency)
• Spectral decomposition
• Acoustic impedance inversion
• Depositional map from posted well curve

10. Depth Conversion

• Type of depth/velocity modeling
• Velocity modeling
• Depth conversion
• Tie the map to well data
• Revising map after drilling
• Map migration

11. Reservoir Characterization

• Acoustic impedance inversion
• AVO Inversion (gradient, intercept, curvature, P-impedance, S-impedance, Vp/Vs, Poisson ratio, Lambda-Rho, Mu-Rho, density)
• AVO crossplot
• Geobody Extraction
• Overpressure detection
• Direct hydracarbon indicator (DHI)
• Sweetness Volume
• Reservoir outline (2D & 3D)
• Reservoir properties (porosity, density & permeability)
• Fluid distribution outline (2D and 3D)
• Fluid properties (composition, viscocity, density, pressure)
• Volume calculation
• Time lapse monitoring (4D monitoring)
• Static Reservoir Modeling

12. Seismic Modeling

• Forward Modeling
  1. 1D modeling:
  • Synthetic seismogram,
  • fluid substitution,
  • well log reconstructions
  2. 2D modeling:
  • Seismic gathers
  • Angle stack
  • Full stack: un-migrated, migrated
• Inverse Modeling
  1. Acoustic Impedance inversion
  2. AVO inversion
• Matching: matching of inverse modeling and forward modeling, can be done in several stages

13. Volume Calculation

• Area vs. thickness plot
• Deterministic calculation (analytical calculation)
• Monte Carlo Simulation

14. Risk Analysis

• Reservoir
• Trap
• Seal
• Source
• Migration path way
• Timing of migration

15. Pressure Prediction

16. Structural Restoration

• Cross section balancing
• 2D seismic restoration
• 3D seismic restoration

17. Others supporting process/interpretation

• Well site geology: cutting, well log, pressure and fluid test, sidewall core, core, VSP
• Seismic Field Acquisition
• Seismic processing
• Reservoir static modeling
• Petrophysics
• Rock Physics
• Basin modeling
• Outcrop studies
• Exploration geochemistry
• Multi component seismic
• Cross well tomography

The fast five and the easy sixth

1. Interpret geologically continuous regional markers such as MFS and SB.
2. Choose the prominent horizons to be the hooked horizons
3. Interpret on a big scale
4. Zoom in and snap the horizons, tidy up the horizons
5. Use journal to record the activities and interesting finding

6. Use relative AI for SB interpretation, local flooding surface or MFS on small basins