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Steps in Geotechnical Procedure for Prioritizing Petroleum Prospectivity in New Exploration Areas

  1. PETROLEUM GENERATION/MIGRATION (THE KITCHEN)

    1. Is the existence of a kitchen already clearly demonstrated by the documented presence of producing fields, shows, and seeps? If so, where is the kitchen? Where has generated petroleum gone? When? Through what did it migrate? Make maps showing all this.

    2. If no kitchen can be demonstrated, then:

      1. What are the stratigraphic units that contain possible source rocks (SR)?

        1. Are they from one of the seven known marine worldwide anoxic events (i.e., are they Silurian, Upper Devonian, Pennsylvanian-Lower Permian, Upper Jurassic, Aptian-Albian, Turonian, or Oligocene-Miocene)? What is the evidence?

        2. Otherwise, are there local marine anoxic units or lacustrine fine-grained units that could contain HC source rocks? Evidence? Localized humicrich units?

        3. For all suspected SR units, make maps documenting control and dimensions/values of:

          1. Areal extent

          2. Thickness

          3. Richness (TOC or SPI)

          4. HC type (oil, mixed, gas)

      2. Did they generate oil or gas (thermal history)? When (timing)? TTI evidence? Peak generation reached? Evidence (VR, coal rank, TAI, etc.)? Make maps.

      3. Where did the generated petroleum go? Evidence? Make maps.

        1. Routes

        2. Concentration

        3. Efficiency (horizontal vs. vertical migration, impedance)

        4. Compare with production and shows

      4. Critical uncertainties—What are they?

        Can they be resolved or reduced?

        1. Before deciding to enter area: Cost?

          Confidence in results? Time?

        2. Before deciding to drill: Cost? Confidence in results? Time?

  2. RESERVOIR ROCKS

    1. Are some reservoir objectives already demonstrated by economic production? Where? Map their probable extent, thickness, and quality.

    2. If some or all reservoir objectives are suspected or projected:

      1. What are the stratigraphic units containing them? Evidence? Show on columnar section.

      2. For all inferred reservoir objectives, make maps showing control and dimensions/values:

        1. Areal extent

        2. Thickness

        3. Reservoir quality (sand%, net-to-gross, % porous, % permeable, etc.)

        4. Depositional environment/provenance/mineralogy; analog examples

        5. Abruptness of lateral facies changes (reservoir rocks to lateral seal)

        6. Comment: Preference should be given to reservoir units overlain by potential sealing units—essential couplet (top seal/reservoir)

      3. Critical Uncertainties—What are they?

        Can they be resolved or reduced?

        1. Before deciding to enter area? Cost?

          Confidence in results? Time?

        2. Before deciding to drill? Cost? Confidence in results? Time?

  3. TRAPS (CLOSURES)

    1. Are some traps already demonstrated by economic production? What are the trap types? Where located? Size of closures? Map the fairways of occurrence.

    2. For those traps that are predicted, what are the trap types (i.e., anticlinal, fault, combination, stratigraphic, basin-centered [generational], etc.)?

      1. Map trends or fairways of different trap types

      2. What reservoirs would they affect?

      3. Analog examples

      4. Did traps (closures) form before generation/ migration? Evidence?

      5. Are traps favorably located with respect to migration?

      6. Reliability of geological/geophysical data (show areas on maps)

        1. Repeatability—identification and delineation by independent workers

        2. Reliability of geological/geophysical data (show areas on maps)

          1. acquisition

          2. time-depth conversions

          3. processing

          4. variable reliability among different trap types

          5. map your confidence in seismic interpretation

          6. 2-D vs. 3-D—resolution vs. cost

      7. Critical trap uncertainties—What are they? Can they be resolved or reduced? By seismic? Other geophysical methods? Geologic methods?

        1. Before deciding to enter area: Cost?

          Confidence in results? Time?

        2. Before deciding to drill: Cost? Confidence in results? Time?

  4. CONTAINMENT

    1. Is containment already demonstrated by economic production? What aspect of containment (top seals? fault seals? lateral permeability barriers?) Where? Map them.

    2. Where containment is not proven and must be predicted:

      1. What are potential top seals, seat seals, and lateral seals? Where are they developed? Map them.

      2. Preservation—make HC-gravity and HC-type maps

        1. Thermal—map areas of thermal immaturity, oil-prone, gas-prone, overcooked (by stratigraphic or structural level). Evidence?

        2. Flushing—salinity and piezometric maps showing ground-water movement

        3. Biodegradation—evidence? manifestations? Map.

        4. Post-accumulation structural adjustments—tilt-and-spill, breaching; locations? Evidence?

      3. Critical containment uncertainties—What are they? Can they be resolved or reduced? How?

        1. Before deciding to enter area? Cost?

          Confidence in results? Time?

        2. Before deciding to drill? Cost? Confidence in results? Time?

  5. PROVISIONAL PLAY IDENTIFICATION, DELINEATION, GRADING

    1. List possible plays (include proven plays showing remaining prospective area of play).

    2. Overlay maps showing kitchen, reservoir, traps, and containment for each play, grade sectors of coincidence.

  6. CRITICAL PLAY UNCERTAINTIES

    1. What are they? List and map.

    2. Can they be economically investigated/resolved in time to influence decision to get into area? Cost? Confidence in resolution? Time required?

    3. Can they be economically investigated/resolved in time to influence decisions to drill? Cost? Confidence in resolution? Time required?

  7. ANALOG BASINS AND PLAYS

    1. Location, geologic succession, tectonic situation, documentation

    2. Elements that are very similar and significant

    3. Elements that are dissimilar and significant

  8. EXPECTED FIELD-SIZE DISTRIBUTION

    1. Source of data and confidence

    2. For analog basin?

    3. For analog play?

    4. Implications for exploration success

  9. DETERMINING MINIMUM ECONOMIC FIELD SIZE (MEFS)

    1. For the proposed area, estimate the cost of exploration (drilling, seismic, other G&G, land, overhead).

    2. At your estimated $PVX% per BOE (for example, $3.50 PV12% per MMBOE), how much total oil must you find to cover the above exploration costs?

    3. What is the smallest field (MMBOE) that could be profitable on a stand-alone basis, assuming several similar producing fields exist in this area?

    4. Divide B by C—Is it reasonable to suppose that many fields exist in the area? Reiterate until you have a reasonable number of economic fields that together would provide the total oil to cover only exploration costs. The average field size is MEFS.

    5. Divide MEFS by play chance to yield operational MEFS.

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