ALPHA NORTH STRUCTURE GEOCHEMICAL STUDY OF FLUIDS (MFT 2 AND MFT 4)

Transcription

1 S. N. E. A. (P) DIRECTION EXPLORATION DIVISION RECHERCHES et APPLICATIONS en GEOLOGIE LABORATOIRE ETABLISSEMENT DE BOUSSENS EP/S/EXP/RAG Lab. Bss n 137/84 RP /cas mm *»*> 50/67 WELL (NORWAY) ALPHA NORTH STRUCTURE GEOCHEMICAL STUDY OF FLUIDS (MFT 2 AND MFT 4) P. CAILLEAUX Boussens Janvier 1 985

2 LISTE DE DIFFUSION DESTINATAIRES HORS DEX : EXPLORATION DIG EUROPE 1 EXPLORATION ELF AQUITAINE NORGE 8 S.I.D. BOUSSENS 2

3 ABSTRACT The main results of the geochemical analysis carried out on the MFT 2 and MFT 4 fluid'samples from 3O/6 7 well is as follows : the oils and the associated gases recovered by MFT 2 ( m) and MFT 4 (265t 2676 m) in the Brent Formation are almost similar. They were sourced by a mature Upper Jurassic source rock as the previously studied 30/6 oils were. 7 pages 2 tables 6 figures

4 Ljyyyyyyi 1 OILS 1 pages 2 ASSOCIATED GASES 2 3 CONCLUSION 2 TABLES Tat. 1 : 3O/6 7 oils : compositions and indices Tab. 2 : 30/6 7 gases : composition and isotopical data FIGURES Pig. 1 and 1 bis : location map Fig. 2 : 3O/6 7 MFT 2 oil : chromatograms Fig. 3 : 30/6 7 MFT 4 oil : chromatograms Fig. 4 : C1/(C2 + C3) vs % n c (CH4) Fig. 5: & 1i C (C2 H6) vs S 13 C (CH4)

5 30/6 00 m Fig. 1 30/6 LOCATION MAP

6 Fig. 1 bis LOCATION MAP «0 en

7 1 Two oil and gas samples, recovered by MFT 2 ( m) and 4 ( m) in the Brent Formation of the 30/S 7 well Alpha North, have been analysed. These two samples come from the only two bottles identified with assurance among the bottles sent by ELF NORGE. Analytical results are given in the tables 1 and 2, the chromatograms of the thermovaporized, saturated and aromatic fractions of the oils are given in the plates 2 and 3. 1 OILS (table 1) The geochemical characteristics(gross composition and chromatograms) show the similarity of the two products. As for the previously studied oils from the 30/6 block*, the A/B ratio = (Pristane/nC17) / (Phytane/n~C1 8) = 1,5 is characteristic of an Upper Jurassic origin. The indices defined on the C5 C15 ch~omatograms (X1 = nc6/methylcyclopentane and X2 = nc7/dimethylcyclopentane) and on the C15+ fraction (Pristane/nC17 and Phytane/nC18) show the two oils have been sourced by a mature source rock in the second half of the oil generation zone. Compared with 3O/6 4 oils*, the saturated fractions of 30/6 7 oils are slightly more mature (particularly lower Pr/n017 and Ph/nC18, 0.5 vs * anct u.53 vs~0.5 respectively). / * 30/6 1 2 and 3 wells : Geochemical analysis of fluids (oil, condensates and gases) P. CAILLEAUX GEO/LAB BSS n 1/2105 RP. 30/6 4 well : Biostratigraphy, sédimentology and organic geochemistry P. CAILLEAUX, P. ROBERT, J. DUCAZEAUX, J.L. VOLAT GEO/LAB BSS n 2/2252 R] 30/6 5 well : Geochemical study of oil P. CAILLEAUX GEO/LAB Bss n 2/231 8 RP.

8 TABLE 1 30/6 7 OILS GROSS COMPOSITION AID CHR01AT0GMPHICAL INDICES TEST Depth G.O.R. (m 3 /m 3 ) Spec. grav. 15C (g/cm 3 ) MPT MFT <n P o o o o H H P P, H m in o cd PHP a o O P o 0)3 DISTILLATE = D ASPHALTENES RESINS SATURATED" H.C. = S AROMATIC H.C. = A S / A S + D 28,9 1, ,8 1, O Xt = nc6/mcp X2 = nc7/dmcp Y1 = nc7/t0l ZTV fo P.T. nalk % TV nalk fo Sat. Pr/nC17 = A Ph/nC17 = B Pr/Ph A / B MCP : methylcyclopentane DMCP : dimethylcyclopentane I _ T0L : toluene TV : thermovaporized fraction (C15 ) Pr, Ph : Pristane, Phytane

9 43^83 ^ SJMEA(P) DIVISION RECHERCHES ET APPLICATIONS EN GEOLOGIE PAYS Country SONDAGE Well : NORWAY = 30/67 *f I» nord) Huile 0/7 Cote m Depth Identification MFT 2 Identification Formation BRENT Fm Formation Age 4 Spec, gravity : 0,852 Fig Composition du produit total (%) Composition of total product FID i^ ~* ^v*^^~'**^^^»^wv\^artlljw u «CM f ** crj If Asphaltenes Asphaltenes Rés i nes Resins HC ' saturss Saturated HC HC aromatiques Aromatic HC Distillat Distillate As R S A D : 1,8 : ,5 = 23,6 : 28,9 JL = 1,63 A HC AROMATIQUES AROMATIC HC, HC SATURES SATURATED HC. HC THERMOVAPORISES THERMOVAPORIZED HC.

10 SNEA(P) DIVISION RECHERCHES ET APPLICATIONS EN GEOLOGIE PAYS Country SONDAGE Well : NORWAY : 30/67 nord) Hu ile O// Cote Depth Identification Identification Formation Formation m MFT4 BRENT Fm Fig. 3 Age Spec, gravity : 0,851 Hi Composition du produit total (%) Composition of total product Asphaltenes Asphaltenes As 1,8 w i 1 1,L 1 ll u 22 iijii in S«Résines Hes ins HC ' saturés Saturated HC HC aromatiques Aromatic Wt Distillat Distillate R S A D : 6,3 : 37,0 : 24,1 : 30,8 S A = 1,53 HC AROMATIQUES AROMATIC HC. HC SATURES SATURATED HC, HC THERMOVAPORISES THERMOVAPORIZED HC.

11 2 2 ASSOCIATED GASES As the oils, the two associated gases (GOR ~ 140) are very similar. Taking into account the isotopical ratios, these wet gases (C2+ = 20 i of total hydrocarbons) are thought to have an origin in a non humic material (Upper Jurassic) and to have a thermogenic origin (i~c4/nc4, Ci/C2 + C3,S 15 C(CH4), cf. diagram on fig.4). Compared with the 30/6 1, 2 and.3 gases*, the representative points of 30/6 7 gases, in the 13 C(C2 H6) vs S 1i C(CH4) diagram (Fig. 5), are located toward the lighter values of S 13 C(CH4). Therefore a very slight input of biogenic gas or a very slight migration effect (STAHL et al. 1975) may not be left out. Owing to the lack of references on gases, the oxygen data are not explained. 3 CONCLUSION The fluids recovered by the MFT 2 and MPT 4 in 30/6 7 are very similar and were sourced by a mature Upper Jurassic source rock as the 30/6 oils previously studied. * Report already mentionned.

12 TABLE 2 30/6 7 ASSOCIATED GASES MOLAR COMPOSITION AND ISOTOPICAL DATA TEST DEPTH G.O.R. N2 C02 C1 C2 C3 ic4 nc4 ic5 nc5 C6+ C1 iol.cn C1/C2 + C3 ic4/nc4 CH4/PDB ioo C2 H6/PDB C02/PDB ioo C02/SM0W MFT A MFT ti I C1 Z Cn = methane % of the total hydrocarbons.

13 10 : 10 4 E l '! I V Older Initially 12 C Depleted fl Produced Gas ZONE OF BIOGENIC ORIGIN I 1 i 1 II 103 _ o o 1 Higher \ Hydrocarbons \ ~ During Migration Depleted \ 1 i MIXING ZONE I 10' ZONE OF PETROGENIC ORIGIN I 30/61,2 I and 3 gases "" <$ 30/6 7 MFT2and4 I I I I I I, C of CH4 in %o Fig / 6 7 <5 13 C (CH 4 ) / PDB Cl/(C2+C3) After Bernard and al, 1977

14 Fig / 6 7 GASES (COMPARISON WITH 30 / 6 1, 2 AND 3 GASES) (CH 4 ) X o o n A A 30/61 DST 1 30/62 DST1 30/67 30/63 DST 2 30/63 DST %o en 01