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Petrology and formation damage control, Upper Cretaceous sandstone, offshore Gabon

Published online by Cambridge University Press:  09 July 2018

E. D. Pittman  and
G. E. King
E. D. Pittman
Affiliation:
Amoco Production Company, Research Center, PO Box 3385, Tulsa, Oklahoma 74102, USA
G. E. King
Affiliation:
Amoco Production Company, Research Center, PO Box 3385, Tulsa, Oklahoma 74102, USA
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Abstract

The subarkosic-sublitharenitic Upper Cretaceous sandstone, which has up to 30% porosity and 585 md permeability, produces on salt diapir structures in the Oguendjo West Block, offshore Gabon. The porosity consists of 68% intergranular porosity of primary and secondary origin, 17% secondary intragranular and moldic porosity, and 15% microporosity. A microcrystalline quartz druse, which was derived from alteration of lithic fragments, coats framework grains and retards the development of syntaxial quartz overgrowths. Other cements are patchy ankerite (0·3–13·7 vol%) and kaolinite, which also occurs as a replacement of framework grains. The total kaolinite content ranges from 1·8 to 8·2 vol%. Kaolinite and remnants of altered and partially dissolved lithic fragments are susceptible to movement with fluid flow. Formation sensitivity tests showed that the kaolinite-rich sandstone was stable to 2% NaCl water, but introduction of freshwater caused permeability impairment. Acid treatment to remove damage produced sporadic results. Injection of HCl raised the permeability temporarily, indicating that fines were still being liberated within the pore network. Injection of HCl/HF immediately reduced permeability through partial disaggregation of the rock. Plugging of the formation face by drill mud also damages the reservoir. Reversal of flow at high pressure differentials will remove formation damage produced by face plugging. A guideline for this process established in the laboratory is to backflow with a pressure differential at least as high as the overbalance used in drilling. The combination of oil-based drilling fluids and underbalanced perforating with filtered diesel in the wellbore should eliminate most formation damage in this reservoir.

Type
Research Article
Information
Clay Minerals , Volume 21 , Issue 4 , October 1986 , pp. 781 - 790
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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References

Allen, T.O. & Worzel, H.C. (1956) Productivity method of evaluating gun perforating. API Drilling and Prod. Practice, 112–125.Google Scholar
Bailey, E.H. & Stevens, R.E. (1960) Selective staining of K-feldspar and plagioclase on rock slabs and thin sections. Am. Miner. 45, 1020–1025.Google Scholar
Dickson, J.A.D. (1966) Carbonate identification and genesis as revealed by staining. J. Sedim. Petrol. 36, 491–505.Google Scholar
Dott, R.H. (1964) Wacke, graywacke and matrix—-what approach to immature sandstone classification. J. Sedim. Petrol 34, 625–632.Google Scholar
Dunn, T.L., Hessing, R.B. & Sandkuhl, D.L. (1985) Application of voice recognition computer-assisted point counting. J. Sedim. Petrol. 55, 602–603.CrossRefGoogle Scholar
Heald, M.T. (1956) Cementation of Triassic arkoses in Connecticut and Massachusetts. Geol Soc. Am. Bull 67, 1133–1154.Google Scholar
Heald, M.T. & Larese, R.E. (1974) Influence of coatings on quartz cementation. J. Sedim Petrol 44, 1269–1274.Google Scholar
Jonas, E.C. & McBride, E.F. (1977) Diagenesis of sandstone and shale: application to exploration for hydrocarbons. Univ. Texas Cont. Educ. Prog. Publ. 1, 165 pp.Google Scholar
Jones, F.O. (1964) Influence of chemical composition of water on clay blocking of permeabifity. J. Petroleum Tech. April, 441–445.Google Scholar
King, G.E., Anderson, A.R. & Bingham, M.R. (1985) A field study of underbalance pressures necessary to obtain clean perforations using tubing conveyed perforating. 60th Ann. SPE Tech. Conf., Las Vegas, SPE Preprint 14321Google Scholar
Krueger, R.F. (1956) Joint bullet and jet performation tests. API Drilling and Prod. Practice, 126–140.Google Scholar
Krueger, R.F., Vogel, L.C. & Fischer, P.W. (1967) Effect of pressure drawdown on cleanup of clay or silt blocked sandstone. J. Petroleum Tech. March, 397–403.Google Scholar
Millot, G., Lucas, J. & Wey, R. (1963) Research on evolution of clay minerals and argillaceous and siliceous neoformation. Clays Clay Miner. 10, 399–412.Google Scholar
Muecke, T.W. (1978) Formation fines and factors controlling their movement in porous media. Proc. SPE Third Syrup. on Formation Damage Control, 83–91.Google Scholar
Pittman, E.D. (1979) Recent advances in sandstone diagenesis. Ann. Rev. Earth Planet. Sci. 7, 39–62.Google Scholar
Versey, H.C. (1939) The petrology of the Permian rocks in the southern part of the Vale of Eden. J. Geol. Soc. London 95, 275–298.Google Scholar