Geochemical Report for. Seabed Cores from Block NOCS 10/7

Transcription

1 Geochemical Report for Seabed Cores from Block NOCS 10/7 n B I'M! v3 Author: Geir Hansen Geolab Nor A/S Homebergveien Trondheim Norway DATE :

2 ESSO NORGE a.s LETING OG PRODUKSJON Den Norske Stats Oljeselskap A/S P.O. Box STAVANGER Attn.: J. Kristensen/T.H. Tan Enterprise Oil Norge Ltd. P.O. Box STAVANGER Attn.: M. Andersen/Ø. Lønne Mobil Exploration Norway Inc. P.O. Box STAVANGER Attn.: K. Espejord/K. Neergaard Norwegian Petroleum Directorate P.O. Box STAVANGER Attn.: E. Tuen Deres ref./your ref.: Vår reuour ref.: S-2770 Dato/Date: Re: Production License Block 10/7 Cores Well 10/7-1 Site Survey Seabed Please find enclosed a geochemical report prepared by Geolab-Nor A/S concerning the analysis of the seabed core samples recovered during the 10/7-1 site survey. As you are aware, equipment problems prevented the collection of more than the three sample Al, Bl and Cl. These samples were recovered from that part of the site survey area in which gas bubbles in the water column had been observed on the high resolution analogue seismic data. The exact locations are as follows: Al, Bl Cl me, me, mn mn UTM31 As described in more detail in the accompanying report, the carbon isotope analysis on the occluded methane gas in sample Cl, indicates that the gas is of thermogenic origin rather than biogenic origin. Although this is an extremely limited data set, it is an encouraging indication that hydrocarbons of thermogenic origin may be present in the subsurface. The results of well 10/7-1 will, of course, be the ultimate test of these observations. Regards, T. Husmo ESSO NORGE a.s 2792thv.06e GRENSEVEIEN 6, POSTBOKS 60, 4033 FORUS TELEFON (04) TELEX N TELEGRAMADRESSE «EXPLORESSO» TELEFAX (04) MEDLEM AV EXXON GRUPPEN

3 Schlumberger GECO-PRAKLA GEOLABMNOR CONTENTS General Comments Interpretation of Data References page APPENDIX 1: TABLES TABLE 1: Sediment Characteristics Data TABLE 2: Occluded Gas Data TABLE 3: Carbon Isotope Data APPENDIX 2: ANALYTICAL PROCEDURES

4 Schlumberger GECO-PRAKLA GEOLABMNOR GENERAL COMMENTS Three frozen sea-bed cores from Block 10/7 were supplied by Esso Norge A/S. Two of the samples were marked "B1" and "C1" respectively, while one was unmarked. The unmarked sample is identified as "A1" in the discussion and in the Tables. The samples were delivered in open liners, making headspace-gas analysis impossible.

5 Schlumberger GECO-PRAKLA GEOLABHUNOR REFERENCES SCHOLL.M. (1983) Genetic characterization of natural gases. AAPG Bull. Vol. 67, No.12, pp

6 APPENDIX 1 TABLES

7 TABLE 1 SEDIMENT CHARACTERISTICS DATA Abbreviations used in the Sediment Characteristics Table %WATER %SAND %CLAY %WATER WS SS % Water of whole sediment used interstitial gas analysis. % of dried material > 63 i.m % of dried material < 63 urn % Water of sieved material used adsorbed gas analysis. in the in the

8 Schlumberger GECO-PRAKLA GEOLABSBNOR L5-Jun-92 Block 10/7 SURFACE GEOCHEMISTRY PROGRAM 14:32:26 SEDIMENT CHARACTERISTICS Page SAMPLE Al Bl Cl % WATER WS %SAND %CLAY % WATER SS

9 TABLE 2 OCCLUDED GAS RESULTS Following abbreviations are used in the Occluded Gas Table. All results in ng gas/g wet sediment (= ppb). C1 C2 C2ene C3 C3ene IC4 NC4 C4ene NeoC5 CyC5 2-meC4 NC5 C5ene 2,2dmC4 CyC6 MecyC5 2-meC5 3-meC5 NC6 C6ene MecyC6 2-meC6 Methane Ethane Ethene Propane Propene Isobutane (2-methylpropane) N-Butane Butene Neopentane (2,2-dimethylpropane) Cyclopentane 2-methylbutane (Isopentane) N-Pentane Pentene 2,2-dimethylbutane Cyclohexane Methylcyclopentane 2-methylpentane 3-methylpentane N-Hexane Hexene Methylsyclohexane 2-methylhexane (Isoheptane)

10 Schlumberger GECO-PRAKLA GEOLABBNOR l-jun-92 ESSO SURFACE GEOCHEMISTRY SAMPLES 14:42:54 OCCLUDED GAS STATISTICS...WET. Results in PPB ID NO. Cl C2 C3 IC4 Al Bl Cl ID Al Bl Cl NO. NC NC NC ID Al Bl Cl NO. C2ene C3ene C4ene C5ene C6ene ID Al Bl Cl NO. neoc5 2-meC ,2-dmC42-meC meC5.416 ID Al Bl Cl NO. cyc5 cyc6 mecyc5 meeye6

11 TABLE 3 CARBON ISOTOPE DATA OCCLUDED GAS All results are presented as % o 8 13 C relative to PDB (Pee Dee Belemnite).

12 Schlumberger GECO-PRAKLA GEOLABMNOR ll5-jun-92 RESULTS FOR Block 10/7 114:28:20 ISOTOPE ANALYSIS Page SAMPLE i Al nd DELTA 13C Bl nd Cl nd «No Data

13 APPENDIX 2 ANALYTICAL PROCEDURES

14 Schlumberger GECO-PRAKLA I GEOLABKNOR ANALYTICAL PROCEDURES SEDIMENT WATER CONTENTS The water content of all sediments was determined directly by substraction following drying a known weight in a forced draught oven at 40 C. SIMPLE PARTICLE SIZE ANALYSIS The sediments were separated by wet sieving into two fractions, < 63 urn, and > 63 im, and the fractions dried at 40 C before weighing. INTERSTITIAL (occluded) GAS ANALYSIS A 50 g (wet weight) aiiquot of total sediment was ball-milled in a sealed container fitted with a septum from which the released interstitial gas was withdrawn for analysis by gas chromatography. The interstitial gas was analysed on either a Perkin Elmer model 8310, or a Varian 3400 gas ehromatograph. A 50 m Plot Fused Silica column with 0.32 mm internal diameter coated with 5jim AlgCyKCl film (Chromopack inc.) were used in both gas chromatographs. The temperature program on the column has an initial temperature of 70 C, 12 C/min heating rate up to 200 C held for 5 mins. The detectors are standard FIDs. Correlation and quantification is achieved by use of external standards.

15 Schlumberger GECO-PRAKLA GEOLABBJNOR ISOTOPE ANALYSIS A 1 ml aliquot of adsorbed gas was analysed for the concentration of 13 C isotope composition of methane relative to PDB (Pee Dee Belemnite) on a Hewlett Packard 5890 A gas chromatograph coupled to Isochrom 2 Mass Spectrometer. The gas chromatograph was fitted with a 25 m Plot Fused Silica column with an internal diameter of 0.32 mm coated with 10 \im Paraplot Q film. The temperature program of the column has an internal temperature of -40 C (cooled down by liquid Nitrogen) held isothermally for 2 minutes, heated at a rate of 8 C/min to -10 C, and further heated at a rate of 15 C/min up to 200 C with a final holdtime of 5 minutes.