Displacement pressure estimation from pore size
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Critical Elements of the Trap |
| Chapter | Evaluating top and fault seal |
| Author | Grant M. Skerlec |
| Link | Web page |
| Store | AAPG Store |
Method
Displacement pressure can be estimated from pore size using Washburn's[1] equation,
Techniques for estimating r
Pore throat radius, r, can be estimated in three ways:
- Thin-section analysis of pore throats[2][3][4][5]
- Thin-section analysis of grain size and assumptions of spherical grains and rhombohedral packing[6]
- Empirical correlation of permeability, porosity, and pore throat radius[7][8][5][9]
Although these methods can estimate the Pd of sands, they do not apply easily to shales and finer grained rocks that comprise top seals. The assumptions of spherical grains and rhombohedral packing used to infer pore throat radius to not apply to shales that contain plate-like clay minerals.[6] Nor is the pore-size distribution easily determined from thin sections of fine-grained shales[10] Use of permeability and porosity is thwarted by the lack of a distinct apex in the mercury injection data of low-permeability rocks[9] as well as the difficulty of measuring the permeability of shales.
Theory and experiment
Predicting top seal capacity is difficult—even in idealized experiments in which all variables are known to a degree unobtainable in practical prospect assessment. The predicted height of hydrocarbon columns calculated from pore throat diameters in uniform glass bead packs is 160–500T larger than heights actually observed in experiments.[11] If we cannot predict the height of hydrocarbon columns trapped in a controlled experiment with uniform glass beads and known variables, then we must be cautious in prospect analysis.
See also
- Measuring displacement pressure using mercury injection
- Estimating displacement pressure from sedimentary facies and well logs
References
- ↑ Washburn, E., W., 1921, Note on a method of determining the distribution of pore sizes in a porous material: Proceedings of the National Academy of Science, vol. 7, p. 115–116.
- ↑ Dullien, F., A., L., Dhawan, G., K., 1974, Characterization of pore structure by a combination of quantitative photomicrography and mercury porosimetry: Journal of Colloid and Interface Science, vol. 47, no. 2, p. 337–349., 10., 1016/0021-9797(74)90265-3
- ↑ Etris, E. L., D. S. Brumfield, R. Ehrlich, R. and S. J. Crabtree, 1988, Relation between pores, throats and permeability: a petrographic/physical analysis of some carbonate grainstones and packstones: Carbonates Evaporites, volume 3, 17–32.
- ↑ Macdonald, I F., P. Kaufmann, and F. A. L. Dullien, 1986, Quantitative image analysis of finite porous media 2: Specific genus of cubic lattice models and Berea sandstone: J. Microscopy, vol. 144, p. 297–316.
- ↑ 5.0 5.1 Wardlaw, N. C., 1990, Quantitative determination of pore structure and application to fluid displacement in reservoir rocks, in J. Kleppe, E. W. Berg, A. T. Buller, O. Hjemeland, and O. Torsaeter, eds., North Sea Oil and Gas Reservoirs: London, Graham & Trotman, p. 229–243.
- ↑ 6.0 6.1 Berg, R. R., 1975, Capillary pressure in stratigraphic traps: AAPG Bulletin, vol. 59, no. 6, p. 939–956.
- ↑ Wardlaw, N. C., and R. P. Taylor, 1976, Mercury capillary pressure curves and the interpretation of pore structure and capillary behavior in reservoir rocks: Canadian Petroleum Geology Bulletin, vol. 24, no. 2, p. 225–262.
- ↑ Wells, J. D., and J. O. Amafuele, 1985, Capillary pressure and permeability relationships in tight gas sands: SPE/DOE paper 13879.
- ↑ 9.0 9.1 Pittman, E. D., 1992, Relationship of porosity and permeability to various parameters derived from mercury injection-capillary pressure curves for sandstone: AAPG Bulletin, vol. 76, no. 2, p. 191–198.
- ↑ Krushin, J., 1993, Entry pore throat size of nonsmectite shales, in J. Ebanks, J. Kaldi, and C. Vavra, eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.
- ↑ Catalan, I., L. F. Xiaown, I. Chatzis, and F. A. L. Dullien, 1992, An experimental study of secondary oil migration: AAPG Bulletin, vol. 76, no. 5, p. 638–650.
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