ANOMALOUS POROSITY PRESERVATION IN THE LOWER CRETACEOUS NAHR UMR SANDSTONE, SOUTHERN IRAQ
Аннотация и ключевые слова
Аннотация (русский):
Core description, well logs data, petrographic analysis and scanning electron microscopetechnique were conducted to unravel factors controlling the preservation of high porosity upto 25% in deeply-buried sandstones > 4 km of the Lower Cretaceous Nahr Umr reservoir,southern Iraq. The Nahr Umr Formation composed of sandstone interbedded with shale,minor siltstones and streaks of limestone. The sandstones are arenites and range from fine tocoarse, and poor to moderate sorted. Parallel lamination, planer cross-bedded and lenticularbedding are common sedimentary structures found in the formation, suggesting that the NahrUmr deposited in fluvial-deltaic to the shallow-marine environment. Cementation by syntaxialquartz overgrowth was retarded by the presence of illite coats, which was formed by theillitization of the infiltrated smectite that formed during the deposition around the quartzgrains. Microquartz coats in the form of quartz crystals probably further prevented the quartzovergrowths. Thus, the porosity of Nahr Umr preserved by the illite coats and microquartzcrystals, whereas, the process of K-feldspar dissolution has created secondary porosity. Thestylolite formation and the quartz-calcite replacement are the main sources of silica for theprecipitation of quartz overgrowth.

Ключевые слова:
Porosity preservation, quartz cement, Nahr Umr Formation, reservoir quality, sandstone reservoir
Текст
Текст произведения (PDF): Читать Скачать
Список литературы

1. Al-Dabbas, M. A., J. A. Al-Jassim, A. I. Qaradaghi (2012), Siliciclastic deposit of the Nahr Umr Formation, sedimentological and depositional environment studies, central and southern Iraq, Arabian Journal of Geosciences, 6, 4771-4783, Crossref

2. Al-Khafaji, A. J. (2014), The Mishrif, Yamama, and Nahr Umr reservoirs petroleum system analysis, Nasiriya oilfield, Southern Iraq, Arabian Journal of Geosciences, 8, 781-798

3. Alsharhan, A. S. (1991), Sedimentological interpretation of the Albian Nahr Umr Formation in the United Arab Emirates, Sedimentary Geology, 73, 317-327

4. Alsharhan, A. S. (1994), Albian Clastics in the Western Arabian Gulf Region: a Sedimentological and Petroleum-Geological Interpretation, Journal of Petroleum Geology, 17, 279-300

5. Aqrawi, A. A., J. C. Goff, et al. (2010), Petroleum Geology of Iraq, Scientific Press Ltd, Beaconsfield

6. Bellen, R. C. Van., H. V. Dunnington, et al. (1959), Lexique Stratigraphique International. vol. III, Asie, Fascicule 10a, Iraq, Centre National de la Researche Scientifique, Paris

7. Bjorlykke, K., P. K. Egeberg (1993), Quartz cementation in sedimentary basins, American Association of Petroleum Geologists Bulletin, 77, 1538-1548

8. Burley, D. S., R. H. Worden (2003), Sandstone Diagenesis: The Evaluation of Sand to Stone, Blackwell, Madlen

9. Jassim, S. Z., J. C. Goff (2006), Geology of Iraq, Dolin and Moravian Meseeum, Prague

10. Lander, R. H., E. E. Larese, L. M. Bonnell (2008), Toward more accurate quartz cement models: the importance of euhedral versus noneuhedral growth rates, American Association of Petroleum Geologists Bulletin, 92, 1537-1563

11. McBride, E. F. (1989), Quartz cement in sandstones: a review, Earth Science Reviews, 26, 69- 112

12. Mohammed, A. K. A., J. K. Radhi, S. Z. ALi (2020), Well Logs data prediction of the Nahr Umr And Mishrif Formations in the Well Noor-10, Southern Iraq, Iraqi Geological Journal, 53, No. 2A, 50-67

13. Owen, R. M., S. N. Nasr (1958), Stratigraphy of the Kuwait Basrah area, Habitat of Oil, Weeks L. G. (ed.) p. 1252-1278, American Association of Petroleum Geologists Bulletin, Tulsa

14. Poulos, S. E., M. B. Collins, H. F. Shaw (1996), Deltaic sedimentation, including clay mineral deposition patterns, associated with small mountainous rivers and shallow marine embayments of Greece (SE Alpine Europe), Journal of Coastal Research, 12, No. 4, 940-952

15. Qaradaghi, A. I., B. M. Abdul-Kareem, et al. (2008), Petrography, diagenesis and depositional environment of Nahr Umr Formation, from selected wells in Central Iraq, Iraqi Bulletin of Geology and Mining, 4, No. 1, 67-94

16. Storvoll, V., K. Bjørlykke, et al. (2002), Porosity preservation in reservoir sandstones due to graincoating illite: a study of the Jurassic Garn Formation from the Kristin and Lavrans fields, offshore MidNorway, Marine and Petroleum Geology, 19, No. 6, 767-781

17. Tang, L., J. Gluyas, S. Jones (2018), Porosity preservation due to grain coating illite/smectite: Evidence from Buchan Formation (Upper Devonian) of the Ardmore Field, UK North Sea, Proceedings of the Geologists’ Association, 129, No. 2, 202-214

18. Taylor, T. R., M. R. Giles, et al. (2010), Sandstone diagenesis and reservoir quality prediction: models, myths, and reality, American Association of Petroleum Geologists Bulletin, 8, 1093-1132

19. Wooldridge, L. J., R. H. Worden, et al. (2017), Biofilm origin of clay-coated sand grains, Geology, 45, 875-878

20. Worden, R. H., S. Morad (2000), Quartz Cementation in Sandstones, BlackwellScience, Malden

21. Worden, R. H., M. W. French, E. Mariani (2012), Amorphous silica nanofilms result in growth of misoriented microcrystalline quartz cement maintaining porosity in deeply buried sandstones, Geology, 40, No. 2, 179-182

Войти или Создать
* Забыли пароль?