1. INTRODUCTION 2. INTERPRETATION OF SEISMIC...Geophysical interpretation of lines 06-05, 06-06, 06-07 No. STU / Y / J / 0005 Page 11 STU-019-pdf.doc-tt/20 March 2007 Mapping of Top

INEOS ENTERPRISE LTD Stublach gas storage project Geophysical interpretation of lines 06-05, 06-06, 06-07

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STU-019-pdf.doc-tt/20 March 2007

CONTENTS

1. INTRODUCTION ............................................................................................................3

2. INTERPRETATION OF SEISMIC ..................................................................................3 2.1. Available data .................................................................................................................3 2.2. Tying of sections.............................................................................................................3 2.3. Picking of sections ..........................................................................................................5 2.4. New Mapping................................................................................................................12

MAIN PURPOSE OF THE REVISION AND TYPE OF MODIFICATIONS

Comments from IECL.


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1. INTRODUCTION Acquisition of the 3 lines 06-05, 06-06 and 06-07 took place in November 2006 by DMT. Processing was performed also by DMT in December 2006-January 2007. The acquisition and processing parameters are displayed in DMT report E6-E1-06-074 dated 26th January, 2007. 2. INTERPRETATION OF SEISMIC 2.1. Available data In order to keep homogeneous data, the seismic sections issued from the DMT processing center have been loaded on the Geoquest charisma workstation. Seismic datum plane is 50 m above Mean Sea Level. The picking has been performed on the PSDM depth converted seismic sections. All the well data issued from INEOS CHLOR (top halite) and HOLFORD (top halite and Bollin mudstone when available) have been loaded in the workstation Quality of seismic is good. Common Deep Point (CDP) spacing is 10 m. The depth sampling rate is 4 meters. 2.2. Tying of sections The reflection is due to the contrasts of density velocity between two layers as:

1122

1122

VρVρVρVρ

R+−

=

12

12

Ζ+ΖΖ−Ζ

=

2ρ : density of lower layer

2V : velocity of lower layer

1ρ : density of upper layer

1V : velocity of upper layer Ζ : acoustic impedance According to the impedance log (velocity density product) recorded in wells DRAKELOW 2A (D2A) and H405, the sudden decrease of density at the top of the salt formation (from 2.55 g/cm3 to 2.05 g/cm3) entails a significant decrease of the impedance log and consequently a negative reflection coefficient generating a negative reflector.


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Well D2A is located some 100 meters north of line 4 and is structurally up dip (by approximately 5 to 10 meters). Well H405 is located Northward of line 4 and equally up dip. The density log has been used to tie the sections. The projection of the well trace on the seismic profile has been performed, applying a depth correction corresponding to the difference between ground level and D. P. A good match appears with the top of the salt (negative phase), and the top of the Bollin mudstones (positive phase triggered by the salt mudstone contrast).

These both reflectors display a good continuity in the target area. The "30 feet marls" bed also generates a good positive reflection. The main silty marl layers interbedded in the salt mass (E, G1, G3 and I) generate reflectors displaying good continuity but of weak amplitude due to their lower impedance contrast. The following horizons have been picked: - Top of Northwich salt - Negative phase. - Top "30 feet marls" - Positive phase - Top Bollin mudstones - Positive phase. The picking of top Northwich, top "30 feet marls" and top Bollin mudstone has been adjusted at the maximum amplitude (positive or negative).

Top of salt

Top of "30 feet marls

Top of Bollin Mudstone


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2.3. Picking of sections Line 06-05

The quality of the both top salt marker and top Bollin marker is good over the whole line. Two main faults affect the salt body. The King Street fault (KSmain) and the Byley fault (BYL1). These faults are normal and show a "horse tail faulting" associated with secondary compensated faults (KSg and Ksg1), (BYL1C). The marker is disturbed between CDP 380 and 390 (BYL1) and 230-290 (KSm). Considering the saliferous formation, the insoluble bands like the 30 feet marls show a clear discontinuity. The top Bollin marls reflector is clearly affected by both these faults with a throw of 20 meters at BYL1 and 30 meters at KSm. The main BYL1 fault affects the "30 feet marls" and generates a weak deflection at the top of the salt, BYL1C does not affect the salt mass. The reflectors show a stratal up turn facies on the King Street fault without overthicknessing suggesting an early, post sedimentary activity. Dragging the density log along the saliferous serie does not show overthicknessing of the salt serie in the direction of the King Street fault. This suggests a lack of synsedimentary tectonic activity.


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Line 06-05 non interpreted

Line 06-05 interpreted


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Line 06-06 The quality of the both top salt marker and top Bollin marker is good over the whole line. The salt is affected by the two faults: KSm (CDP 240) without horse tail facies and BYL1 with the compensated fault BYL1C (CDP 405-450). Concerning BYL1 fault, the both reflectors "30 feet marls" and top Bollin show a clear discontinuity (throw of 26 meters). The intra-salt insoluble beds seem affected. The top of the salt is less affected featuring a slight deflection. The reflectors show a stratal up turn facies on the King Street fault suggesting an early post sedimentary activity.



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Line 06-07 The quality of the both, top salt marker and top Bollin marker is good over the whole line. The top of the saliferous serie is affected by the King Street fault at CDP 238 (horse tail facies KSg) and by the Byley faults (BYL1 and BYL1C) between CDP 388-436 Both the markers 30 feet marls and top Bollin show a clear inflection due to the Byley fault inducing a throw of 50 meters. The top of the salt is less affected, featuring a depression.



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Mapping of Top Northwich salt and Top Bollin mudstone A shift of the seismic data of 50 m has been applied in order to obtain a mean sea level (MSL) referenced map. For the contouring, the depth of the top Northwich salt at the wells has been introduced for the computation of the grid as:

Well Name Depth Mean sea level (m) Top Northwich salt

Salt thickness Top Bollin-Top Northwich (m)

RM73 52.7

RM72 234.9

RM64 218.8

RM62 91.8

D-2A 399.6 267

Byley 411.3

H246 138.2

H402 412.5

H406 437.5

H405 420 258

H407 434

H408 420.5

The top of salt at the INEOS CHLOR wells has been provided by Mr. Robin Craig and integrated in the mapping. The polygon of mapping has been limited at the King Street fault in the western area, due to a poor quality of the seismic in that area. For the "30 feet marls" seven wells were available:

Well name Depth Mean Seal Level (msl) D2-A 622

H402 618

H406 646

H405 632

H407 652

H408 642

H403 615


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For the Bollin mudstones only three wells are available:

Well Name Depth Mean Sea Level (msl)

D2-A 660.1

H246 385.2

H405 698

It is worth to note that the depth of the top salt given by the seismic displays a good match with the well data in the North-East of line 02. The new HGSL wells at Drakelow have been introduced. They suggest a more complicated paleo-topography of the top salt in the south (20 meters nearly depth difference between D2A and H405) The accuracy of the mapping derived from the seismic outside the seismic lines is estimated around 10 meters due to the gridding algorithm applied. 2.4. New Mapping The isobath curves have been computed at ten meters interval. The maps feature a general North-South dipping in the target area of some 7 degrees. The most significant new feature highlighted by the new seismic survey is the BYL1 fault which could be suspected in the former map (North-South trend of the isobath curves). This set of faults isolates a polygon of underlaying basement block on the West edge of the graben. The throw of the fault is around 30 meters for the top Bollin mudstone but induces only a small flexuration at the top of the salt formation. On the isobath map of the Bollin Top mudstones the BYL1 fault has been extrapolated (dashed lines). The area between BYL1 and BYL1C is disturbed by the faults. Some erosional effects may affect the paleo surface. The examination of static corrections indicates on line 06-06 an increase of the thickness of the weathered zone in the area of the fault. This might suggest neo tectonic effects in this area.


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Top Northwich salt isobath map (DP-MSL)


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Top "30 feet marls"


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Top Bollin mudstone isobath map (DP=MSL) - Fault BYL1 appears clearly

Isopachous map - Top halite - Top Bollin

As observed on the seismic section, no significant variation of thickness has generally been observed in the project area: average of 260 meters for the whole halite sequence. A decrease of thickness of 30 meters is however visible on the west edge of the Byley fault.

Documents

1. INTRODUCTION 2. INTERPRETATION OF SEISMIC...Geophysical interpretation of lines 06-05, 06-06, 06-07 No. STU / Y / J / 0005 Page 11 STU-019-pdf.doc-tt/20 March 2007 Mapping of Top