Aquifer properties of the Permo-Triassic sandstones of the United Kingdom
The potential value of core analysis in hydrogeology is critically examined in the light of the results of a systematic study of the porosity, density and intergranular permeability of the Permo-Triassic sandstones in the United Kingdom, based on the examination of 3500 test specimens. The Thesis begins with an account of the stratigraphy of the sandstones, illustrated by 51 vertical sections. This is followed by a description of the distribution and nature of the samples tested. The principal experimental methods employed were the liquid resaturation technique for measurement of porosity and density, and a gas permeameter was used to determine intrinsic permeability. Equipment systems are described which enable large numbers of samples to be handled rapidly. An improved water permeability test system incorporating sterilising filtration is described and tentative proposals for automated instrumentation are presented. The centrifuge method of measuring specific yield is re-examined. The test data are analysed in two ways: a) by making a detailed comparison of the lithology and physical properties of the test specimens, and b) by considering the porosity and permeability data as probability distributions. The second method permits the aquifer properties of the various sandstone subdivisions in different parts of the U.K. to be quantitatively compared for the first time. The parameter "primary" transmissivity is introduced to describe the intergranular component of transmissivity. Values for this parameter are compared with values for "total" transmissivity derived from analysis of pumping test data from six localities in widely differing hydrogeological environments. It is suggested that this comparison allows some general conclusions to be drawn about the relative importance of intergranular flow in sandstone aquifers. A further comparison is made of the permeability and transmissivity of British and German Triassic sandstone aquifers on the basis of data published by Hauthal (1967) and Durbaum, Matthess and Rainbow (1969). The study was deliberately intended to be of a general nature, so as to provide a firm basis for future me detailed work on the hydrodynamic behaviour of sandstone aquifers in the United Kingdom.