SUBSURFACE INTERPRETATION

Oleh Unknown

Sunday 8 May 2016

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Well Data Interpretation

Reservoir Identification

•Gamma Ray (GR) log analysis

–High GR è shale

–Low GR è sandstone or limestone

•Spontaneous Potential (SP) log analysis

–Monotonous è shale

–Deflection è sandstone or limestone

Correlation

•Using Sequence Stratigraphic model:

•Assumption:

–Deterministic model

–Sedimentary architecture controlled by: Relative change of sea level

–Relative change of sea level controlled by Eustatic and Tectonic

•Eustatic global of sea level in sinusoidal form (Harmonic wave)

•Tectonic movement relatively constant

  è Rising and falling of sea level can be identified in log     record

  è Represent time boundaries

  è Good Correlation marker

Correlation

•Sequence Stratrigraphy Hierarchies

–Sequence

–System Tract

–Para sequence

–Bed set

•One Sequence can be bounded by :

–SB and SB

–MFS and MFS

Schematic dip profile illustrate the key sequence stratigraphic surface-sequence boundaries, and maximum flooding surfaces, and their stratigraphic expression. These surfaces serve to subdivide stratigraphic sections into sequences and systems tracts

•Within one sequence theoretically can be divided into three system tracts:

–Lowstand system tract (LST)

–Transgressive system tract (TST)

–Highstand system tract (HST)

• One system tract can be divided into several parasequences.

• Each parasequence bounded by Flooding Surface (FS).

• FS  time boundary good marker for correlation.

• One parasequence can contain several beds or several facies.

Petrophysic Analysis

• Gross thickness

• Net thickness

• Net to Gross

• Water saturation (Sw)

• Pay thickness

• Hydrocarbon contacts (OWC, GOC, GWC, etc)

Gross Thickness

• Define qualitatively by:

– GR log 

– SP log

• Guided by Flooding Surface 

• Measure in TVD

• Gross thickness = bottom - top

Net Reservoir Thickness

• Guided by Gross thickness 

• Applied Vshale Cut Off

• Applied porosity Cut Off

• Vshale using GR

• Vshale = (GR-GRmin)/(GRmax-GRmin)

Note:

GR = GR at cut off

GRmin = Minimum GR reading

GRmax = Maximum GR reading

Net Reservoir Thickness

• Vshale using SP

• Vshale = (SSP – PSP) / SSP Archie Formula (default)

• Swn= (a x Rw) / (Fm x Rt)  

• Shaly sand reservoir:

• Simandoux

• Poupon/Indonesia

•

Note:

SSP = the deflection from the shale line to clean line

PSP = the deflection from the shale line to the curve reading   at zone of interest

Net to Gross Ratio

NTG = Net thickness / Gross interval

Water Saturation (Sw)

Pay Thickness

• Vshale cut off

• Porosity cut off

• Sw cut off

Hydrocarbon Contact

• Based on log analysis

• Based on Flat spot

• Based on RFT plot

• Based on DST

Well and Seismic Integration

• Depth Structure Map

• Gross Reservoir Map

• Iso-porosity Map

• Iso-saturation Map

Depth Structure Map

• Well reservoir picking 

• Seismic to well tie

• Seismic horizon picking

• Time structure map

• Depth structure map

Gross Reservoir Map

• Gross thickness from well data

• Cross correlation between well thickness and Attribute Map

• Generate formula transferring Attribute  Map to Gross Map based on cross plot

• Generate Gross Map

Iso-porosity Map

• Value from well data

• Cross correlation between well porosity and AI seismic map

• Generate formula transferring AI Map to Porosity Map based on cross plot

• Generate Porosity Map

Iso-saturation Map

• Iso-saturation from well data

• Cross correlation between well Sw and AI seismic map

• Generate formula transferring AI Map to Sw Map based on cross plot

• Generate Sw Map

Tag : Geologi, Minyak dan Gas