Changes

===Other techniques===

===Other techniques===

Another technique available for the determination of porosity in addition to those mentioned here is point counting pore space occupied by blue epoxy in thin sections (see [[Thin section analysis]]). Also, significant progress has been made recently in the development of petrographic image analysis (PIA) as a technique for porosity determination.<ref name=pt05r52>Ehrlich, R., Kennedy, S. K., Crabtree, S. J., Crabtree, R. C., 1984, Petrographic image analysis, 1. Analysis of reservoir pore complexes: Journal of Sedimentary Petrology, v. 54, n. 4, p. 1365–1378.</ref><ref name=pt05r66>Gerard, R. E., Philipson, C. A., Bellentine, F. M., Marshall, D. H., 1991, Petrographic image analysis, in Polaz, I., Sengupta, S. K., eds., Automated Pattern Analysis in Petroleum Exploration: New York, Springer-Verlag.</ref> In this process, pore space is delineated from mineralogy using photographic imaging techniques. Taking images from several locations on a thin section allows one to compensate for a three-dimensional parameter from two dimensions.

Another technique available for the determination of porosity in addition to those mentioned here is point counting pore space occupied by blue epoxy in thin sections (see [[Thin section analysis]]). Also, significant progress has been made recently in the development of petrographic image analysis (PIA) as a technique for porosity determination.<ref name=pt05r52>Ehrlich, R., Kennedy, S. K., Crabtree, S. J., Crabtree, R. C., 1984, [http://jsedres.geoscienceworld.org/content/54/4/1365.abstract Petrographic image analysis, 1. Analysis of reservoir pore complexes]: Journal of Sedimentary Petrology, v. 54, n. 4, p. 1365–1378.</ref><ref name=pt05r66>Gerard, R. E., Philipson, C. A., Bellentine, F. M., Marshall, D. H., 1991, Petrographic image analysis, in Polaz, I., Sengupta, S. K., eds., Automated Pattern Analysis in Petroleum Exploration: New York, Springer-Verlag.</ref> In this process, pore space is delineated from mineralogy using photographic imaging techniques. Taking images from several locations on a thin section allows one to compensate for a three-dimensional parameter from two dimensions.

Both X-ray computerized tomography (CT) and nuclear magnetic resonance (NMR) have applications to determining porosity. This is outside the scope of this discussion but is comprehensively covered in the literature (e.g., <ref name=pt05r159>Vinegar, H. J., 1986, X-ray, CT, and NMR imaging of rocks: Journal of Petroleum Technology, v. 38, p. 257–259., 10., 2118/15277-PA</ref><ref name=pt05r167>Wellington, S. L., Vinegar, H. J., 1987, X-ray computerized tomography: Journal of Petroleum Technology, v. 39, n. 8, p. 885–898., 10., 2118/16983-PA</ref>).

Both X-ray computerized tomography (CT) and nuclear magnetic resonance (NMR) have applications to determining porosity. This is outside the scope of this discussion but is comprehensively covered in the literature (e.g., <ref name=pt05r159>Vinegar, H. J., 1986, X-ray, CT, and NMR imaging of rocks: Journal of Petroleum Technology, v. 38, p. 257–259, DOI: [https://www.onepetro.org/journal-paper/SPE-15277-PA 10.2118/15277-PA].</ref><ref name=pt05r167>Wellington, S. L., Vinegar, H. J., 1987, X-ray computerized tomography: Journal of Petroleum Technology, v. 39, n. 8, p. 885–898, DOI: [https://www.onepetro.org/journal-paper/SPE-16983-PA 10.2118/16983-PA].</ref>).

===Effects of confining pressure on porosity===

===Effects of confining pressure on porosity===