1. Borehole Image Interpretation Results Wells: E17a-A1, A2 & A3 Gaz de France - Suez – Netherlands
Mourad KOURTA
Schlumberger, CEU

2. Carboniferous Subcrop Map E17a-A Field
Well Positions
Legend A A’
E17a-A3
E17a-A2
E17a-A1
Presuming everybody is aware of what is Schmidt-net!
Asking the audience  if not, slide 9
Carboniferous Subcrop Map E17a-A Field

3. Bed Boundaries (Structural Bedding)
E17a-A1
E17a-A2
E17a-A3
East Trend
ESE Trend
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
Eastward Trend
SE Trend
SE Trend
U-HPLGRD.
L-HPLGRD
MAURITS (Coal)
MAURITS
PERMIAN
PERMIAN
U-HPLGRD
L-HPLGRD
MAURITS 3

4. Sedimentary and Cross Beds
E17a-A1
E17a-A2
E17a-A3
Sedimentary Beds
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
Cross Beds 4

5. Resistive Fractures (from OBMI)
E17a-A1
E17a-A2
E17a-A3
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
Resistive Fractures 5

6. Low and High Acoustic Amplitude Fractures (from UBI)
E17a-A1
E17a-A2
E17a-A3
Low Acoustic Amplitude Fractures
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
High Acoustic Amplitude Fractures 6

7. Possible Faults
E17a-A1
E17a-A2
E17a-A3
No fault was interpreted
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
Note that the main fault in this well is oriented N-S
Possible Faults 7

8. Borehole Breakouts
E17a-A1
E17a-A2
E17a-A3
Presuming not everybody from the audience is geologist …
Couple of cases that we can use dips in coarse-grained deposits as structural dip indicators (for ex. inter-dune sands in eolian env. or certain sheet-like shallow marine sands etc.).
Sedimentary dip examples from K3-3 and J10-1 OBMI.
Any dip in these sediments – results of tectonic events. Structural geology -> analysing deformations (ductile or brittle) and interpreting reasons, mechanisms that created them + paleo-stress states and directions!
Borehole Breakouts 8

9. Highlights Structural Dip:
High dip angle towards East (A3), relatively low angle towards SE (A1 & A2).
Consistent dip azimuth trend with:
No variations (A1).
Progressive rotation downward from an East (minor) trend to a SE dominant trend (A2).
Minor and localized fluctuations, mainly around 3900 m, with a fault and a drag effect (A3).
Progressive dip steepening downward, related to a fault suspected from seismic data (A3).
Structural dip variations  different structural positions +/- proximity to faults.
Faults:
Minor faults / micro-faults, mainly N-S, with no impact on bedding orientation (A1).
No fault was interpreted in A2.
Well A3:
One N-S fault associated to a drag effect around 3900 m.
Minor faults / micro-faults, mainly E-W with no influence on bedding dip trends.
Possible fault below TD detected from seismic & suspected from steepening of bedding downward.
Bottom line  we have never run an OBMI-UBI combination in the Dutch North Sea for GdF. At least I have never had the chance to look at it …

10. Highlights Geological Boundaries:
Top Carboniferous Unconformity (Top U-HPLGRD):
Well A1:
~ m (unconformable bed / erosive surface).
OBMI image contrast.
Slight lithology change.
Well A2:
At least 2 possible scenarios ~ m ~ m).
Supported by image fabrics, dip type / profile and high resolution image-derived logs.
Sandstone layer: top of Carboniferous or base of Permian??
Well A3:
2 possible scenarios ~ m ~ m).
Supported by image fabrics and change in open hole log responses.
Change in structural dip: low dip angle & scattered dip azimuth (above), higher dip angle, more consistent dip azimuth (below).
Bottom line  we have never run an OBMI-UBI combination in the Dutch North Sea for GdF. At least I have never had the chance to look at it …

11. Highlights Geological Boundaries: Top L-HPLGRD: Well A1:
~ m (unconformable bed / erosive surface).
Good contrast in OBMI image, no clear UBI image.
Clear facies change: cross bedded sandstone below and shaly with no visible bedding above.
Well A2:
~ m.
Supported by the UBI image fabrics, dip type / profile and high resolution image-derived logs.
Other possibilities can also be proposed ~ m or ~ m).
Well A3:
~ m.
Supported by the interpreted unconformable beds, changes in open hole log responses, changes in dip types and in UBI-OBMI image fabrics.
Shape and deflection of high-resolution UBI amplitude and OBMI Rxo curves.
Bottom line  we have never run an OBMI-UBI combination in the Dutch North Sea for GdF. At least I have never had the chance to look at it …

12. Highlights
Geological Boundaries:
Top Maurits:
Well A1:
Not reached.
Well A2:
~ m.
~ m: presence of unconformable bed / erosive surface, change in UBI and OBMI image appearance and resistivity logs.
Well A3:
~ m.
~ m: presence of an unconformable bed, change in UBI and OBMI image appearance (UBI) and resistivity logs.
Bottom line  we have never run an OBMI-UBI combination in the Dutch North Sea for GdF. At least I have never had the chance to look at it …

13. Highlights
Geological Boundaries:
Top Maurits:
Well A1:
Not reached.
Well A2:
~ m.
~ m: presence of unconformable bed / erosive surface, change in UBI and OBMI image appearance and resistivity logs.
Well A3:
~ m.
~ m: presence of an unconformable bed, change in UBI and OBMI image appearance (UBI) and resistivity logs.
Bottom line  we have never run an OBMI-UBI combination in the Dutch North Sea for GdF. At least I have never had the chance to look at it …