33 4 2014 12 GLOBAL GEOLOGY Vol. 33 No. 4 Dec. 2014 1004-5589 2014 04-0875 - 05 1 2 1 2 1. 130026 2. 830011 PND SIGMA CATO SIGMA CNL 0. 91 SIGMA CATO P631. 325 A doi 10. 3969 /j. issn. 1004-5589. 2014. 04. 015 Research on explaining porosity in carbonate reservoir by capture cross section method ZHAO Qin 1 MA Li-xin 2 MO Xiu-wen 1 WANG Qin-cong 2 1. College of Geo-exploration Science and Technology Jilin University Changchun 130026 China 2. Engineering Technology Institute of Northwest Oilfield Branch Company SinoPEC Urumchi 830011 China Abstract The cracks and fracture-caves are very developed in Tahe oilfield composed mainly of carbonate reservoir which affects the acquisition and accuracy of conventional logging data. When the conventional logging data can not be obtained capture cross section of PND can be used to explain the porosity of reservoir. According to the relationship among CATO saturation and porosity the authors proceed the saturation correction of SIGMA. The results of porosity calculation is better consistent with of CNL showing 0. 91 in correlation coefficient which proved the efficiency of porosity calculation by SIGMA with CATO and provided a new method of porosity interpretation when cracks and fracture-caves developed in carbonate reservoirs. Key words capture cross section porosity inelastic scattering measurement carbonate reservoir assessment 0 1-6 PND 2013-08-23 2014-06-26 3C1128674423. 1970 -. E-mail moxw@ jlu. edu. cn
876 33 CATO 7 CATO 3 C /O C /O 4 8 9 CATO Σ = Σ ma 1 - φ + Σ w * S w * φ + Σ h 1 - S w * φ 2 1 φ = Σ - Σ ma - Σ Σ h * S w - Σ ma + Σ h 3 w Σ ma Σ w Σ h φ S w Σ = V i Σ i 1 i Σ Σ i i V i i 2 CATO 1 CATO PND 1 Σ 10 Table 1 Thermal macroscopic capture cross section Σ of common rock matrix and minerals C /O 11 C /O Σ c. u. Σ c. u. 12 C /O SiO 2 4. 25 7 ~ 14 CaMg CO 3 2 4. 8 7. 5 ~ 9. 5 CaCO 3 7. 2 8 ~ 3 NaCl 726. 0 20 ~ 40 B 759. 0 18 ~ 22 Cl 33. 6 10 MPa 40 3. 8 22. 2 200 g /L 100 CATO a b c d 3. 74 10 22 cm - 3 2. 66 10 22 cm - 3 3. 35 10 22 cm - 3 4. 89 1 1 10 22 cm - 3 CATO T Σ Σ CATO 13 Σ 2
4 877 T = b 1 - φ + aφ 1 - S w cφs w + d 1 - φ 4 φ S w φ T φ = ad - S w ad + bc 5 + d 1 - φ 2 cφs w CATO CATO CNL CNL = a 0 + a 1 x 1 + a 2 x 2 + a 3 x 1 x 2 + a 4 x 2 1 + a 5 x 2 2 6 T φ S w 0. 672 38 < 67. 238% SIGMA T > 67. 238% T 3 5 T 1 1 CATO T S w Fig. 1 Relationship between water saturation S w and CATO index T a 0 a 1 a 2 a 3 a 4 a 5 x 1 CATO x 2 CNL 2 A807 4 510. 00 ~ 5 870. 00 m 5 661. 37 m 5 697. 50 m 5 697. 50 ~ 5 701. 00 m 5 704. 00 ~ 5 706. 61 m 5 717. 50 ~ 5 721. 12 m 5 730. 58 ~ 5 731. 00 m PND 5 698 m 5 730 m PND SIGMA CATO SIGMA 14 CATO SIGMA 5 CATO S w CATO 2 CNL Fig. 2 Compared of synthetic porosity with CNL multi-well SIGMA
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