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MK - GMB - 12 Subsurface Mapping

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    Lesson-12Reserve and Resource

    Estimation

    Edi B. Setyobud i2014

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    Further Readings

    Tearpock, D.J. & R.E. Bischke, 1991

    “Applied Subsurface Geological Mapping” – 

    Chapter 14

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    How to Phantom Down

    Formation Top =

    Seismic Marker

    Reservoir Top

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    Maps Needed

    Structure Maps

    Thickness Maps:

    Isopach (Isochore) Map

    Isochron Map (seismic time interval)

    Other Maps:

    Porosity Map

    Net / Gross Ratio Map

    Etc

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    Gross  – Net Thickness and Net Pay

    Gross Thickness:

    Formation / member

    Zone

    Reservoir (sand / carbonate / others) Net Thickness:

    Portion of the thickness that porous and permeable – eg

    above cut-offs

    Net Pay:

    Portion of Net thickness that contains producible

    hydrocarbon – eg above saturation cut-offs

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    Gross  – SandThickness - Ratio

    Formation thickness:• Well A – 605’ 

    • Well B – 701’ 

    Gross sand thickness:

    • Well A:• Sand-1 – 99’ 

    • Sand-2 – 101’ 

    • Sand-3 – 103’ 

    • Well B:

    • Sand-1 – 102’ • Sand-2 – 151’ 

    • Sand-3 – 129’ 

    Well A Well B

    Sand – Shale Ratio: Well A: 303’ / 605’ = 0.50 

    Well B: 382’ / 701’ = 0.54 

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     Any special purpose map such as Sand Shale Ratio Map,

    Porosity Map – you name it – can be generated

    Formation Thickness Map - Isochore

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    Net Sand Isochore Map

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    Pay Thickness

    Pay – 

    portion of

    reservoir

    that

    containsproducible

    hydrocarbon

    • Net oil• Net gas

    Phantoming down – use gross thickness map

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    Bottom and Edge Water

    Bottom Water Edge Water

    Pay attention to geometry differences

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    Bottom Water

    Key Components:

    • Structure map on top

    • Oil Water Contact

    Net Pay Map Construction

    Very simple task:

    • Subtract contour values

    with OWC number

    • Adjust to net values

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    Edge Water Reservoir

    Key Components:

    • Structure on top

    • Structure on base

    • Oil water contact

    • Net sand thickness

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    Key Components:

    • Structure on top• Structure on base

    • Oil water contact

    • Net sand thickness

    Edge Water

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    Edge Water  

    Important aspects:

    • OWC on top – marksouter limit of oil - blueline  

    • OWC on base – marks

    inner limit of water –inside this line:

    net sand = net pay – redline

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    Edge Water - Detail Procedure-1

    1. Draw depth structure

    map on top reservoir – 

    mark OWC – blue line

    2. Draw depth structure

    map on base reservoir

     – mark OWC – red line  

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    3. Take net sand isochore

    map – draw OWC on

    base (red line)

    4. Remove contour

    outside the circle

    5. Draw OWC on top(blue line)

    Edge Water - Detail Procedure-2

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    Edge Water - Detail Procedure-3

    6. Connect contour

    lines – start from

    thickest part

    7. Complete thecontour lines as

    necessary

    8. Planimeter the map

    to calculate net oil

    sand volume

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    Edge Water Reservoir  – Oil and Gas

    GASGAS / OIL

    CONTACT

    Key Components:• Structure on top

    • Structure on base

    • Oil water contact

    • Gas oil contact

    • Net sand thickness

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    1. Draw depth structure map

    on top reservoir – mark

    OWC – blue line  and GOC – red line

    2. Draw depth structure map

    on base reservoir – mark

    OWC –  green line  andGOC – brown line

    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-1

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    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-2

    3. Take net sand isochore

    map – draw GOC on base

    4. Remove contour outside

    the circle

    5. Draw GOC on top

    6. Connect contour lines – 

    start from thickest part

    7. Complete the contour linesas necessary

    8. Net gas pay map done

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    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-3

    9.Draw:OWC on top (blue),

    OWC on base (green),

    GOC on top (red),

    GOC on base (brown)

    Note:

    •  area between OWC

    on base and GOC on

    top – full net sand

    thickness

    •  Area inside GOC on

    base – no oil zone

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    10. A) Overlay NetSand Map

    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-4

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    10. B) Remove contourlines outside full netsand thickness

    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-5

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    Edge Water Reservoir  – Oil and Gas:

    Detail Procedure-6

    11. Complete contour

    lines as necessary

    Final products:

    • Net gas pay

    • Net oil pay

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    Rock Volume Calculated Slice by Slice

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    Rock Volume Slices (Vb)

    Trapezoidal

    Pyramidal

    Where:

    •  An  = area of one contour

    •  An+1  = area of the next contour

    • h = contour interval

    Note: if An/An+1 > 0.5 use Trapezoidal

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    Calculate Reservoir Volume

    •  Add all slices from

    bottom up

    • Never miss the

    volume of crestal

    point

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    Initial Hydrocarbon In Place

     Symbol Remarks IHCIP Initial hydrocarbon in place 

     Resv Volume Reservoir volume 

    Ф 

     Porosity 

    (1 – Sw) Hydrocarbon saturation 

     FormationVolume Factor 

     Ratio of HC in reservoir vs atsurface 

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    Thanks for your

    kind attention

    Fruits & Veggies Juices


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