Anomaly apical

The absorption of short-chain weak acids in the rat intestine, as a function of pH, does not appear to conform to the pH partition hypothesis [44]. Similar anomalies were found with weak bases [77]. The apparent pKa values observed in the absorp-tion-pH curve were shifted to higher values for acids and to lower values for bases, compared with the true pKa values. Such deviations could be explained by the effect of an acid layer on the apical side of cells, the so-called acid pH microclimate [44,70,73,76-84],... 

According to Kartsev et. al. (1959), Sokolov (1970), Horvitz (1986) and Fei and Ruan (1991), gas microseepage associated with petroleum has three characteristic styles of surface anomaly (1) apical (2) aimular and (3) linear. One or any combination of these surface expressions may occur over a given oil or gas field. 

An apical anomaly comprises either a continuous zone of elevated gas concentrations or an area with erratic elevated gas concentrations directly over the oil or gas field. An annular or halo anomaly has the form of a doughnut of continuous or discontinuous high gas concentrations surrounding a central zone of lower or background values, the latter overlying the surface projection of the oil or gas field. In a linear or belt anomaly, high gas concentrations are found continuously or intermittently along a line or confined in a belt, usually associated with faults, fracture zones, or matured source beds. 

It is vital, but not necessarily easy, to recognise whether an anomaly is apical, annular or linear, because the interpretation placed upon each of them leads to quite different courses of action. The model used to explain an apical anomaly favours drilling the anomaly peak, whilst the model for an annular anomaly favours the area within the ring of high values. Follow-up of linear anomalies needs to take into account structural or lithological information. 

Subsequently the scientific research well was drilled as planned. When it penetrated Lower Ordovician carbonates it produced 16.3 x lO" m per day of natural gas. The scientific research well thus became the discovery well in this region. Since the well was drilled directly on the surface hydrocarbon gas anomaly, the soil gas survey traverse was thought to cross an apical or linear anomaly. Further work, however, was to reveal that the gas field has an annular anomaly. 

Gas geochemical surveys of light molecular-weight hydrocarbons (C1-C5) and Hg have proved to be useful methods of detecting oil and gas fields in the Ordos Basin of northern China and of indicating potential oil or gas fields in the Lixian Depression of southern China. The annular anomaly is the type most usually found in these regions, although apical and linear anomalies occur under particular conditions. 

Fig. 66. High-resolution neutron difiraction at r = 5K of BAO samples (sect. 3.2.2.4). (a) With increasing oxygen content the dimpling increases. The dimpling anomaly corresponds to the c-axis anomaly (fig. 29f) at x = 6.93, earlier found using X-rays by Rusiecki et al. (1990), cf fig. 28a. (b) The apical bond shows only a very small anomaly. After Conder et al. (1994a) and Hewat et al. (1991).

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