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Analysis of produced water is one of few direct sources of information to the subsurface processes active in an oil field. However, revealed geochemical patterns are typical complex and require a multidisciplinary approach to successfully unlock and decode. The Halfdan field initially contained two main types of formation brine but now, after 15 years of extensive water flooding, the field contains mostly a seawater modified type. The initial water was a low salinity sulphate-depleted type and a medium high saline sulphate-rich type that varied in a geographically systematic manner. The water treatment resulted in a net deposition of sulfate and Mg and a net export of Ca and Cl ions from the field. This pattern is similar to core flooding results, suggesting that a substantial alteration of the wettability of the chalk occurred. Spatial and temporal variation in water composition are mapped based on 3880 analysis from 75 wells and are related to water flooding history and sweep efficiencies obtained from 4D seismic. Produced water analysis is thus an important asset for designing water sweep in mature fields. Furthermore knowledge about the initial water types may optimize water treatment and prediction of geographically distribution scale and corrosion risks.

Pyroxene fractionation trends in igneous rocks depend on the magma composition and the conditions of crystallization. Four main types of pyroxene crystallization trend have been recognized in terrestrial igneous rocks (Fig. 1). These are the clinopyroxene trend of mildly alkaline basic magmas1,2; the clinopyroxene trend of strongly alkaline basic magmas3; the two-pyroxene trend typical of tholeiitic magmas4–6; and the two-pyroxene trend typical of calc-alkaline intrusions7–9. The calc-alkaline pyroxene trends show restricted iron-enrichment as high causes the crystallization of calcic amphibole (and biotite) in place of pyroxenes at a fairly early stage of fractionation. Ca-rich and Ca-poor pyroxenes from the Fongen–Hyllingen complex which coexist with hydrous mafic phases and initially have compositions very similar to those from calc-alkaline complexes, show extreme iron-enrichment in the late differentiates. This is the first recorded example of such extreme pyroxene fractionation in elevated conditions and this fractionation trend, accompanied by other distinct mineralogical features, warrants designation as a new type: the Fongen–Hyllingen trend.

This poster illustrates the lecture on Pattern Recognition and gives recently published and unpublished examples, mainly from the laboratory from the first author. The applications concern: - the determination of metabolic pathways of branched chain fatty acids (by clustering), - the development of a genetic classification of meteorites (by clustering), - the classification of cholinergic agents according to their interaction with different receptors (by clustering), - the structure of a data set consisting of gaschromatographic profiles in samples collected in pollution monitoring stations (by factor analysis and pattern recognition), - factors determining GLC behaviour of solutes (by factor analysis and multiple regression), - the classification of olive oils according to geographic origin (by principal components and pattern recognition), - the diagnosis of thyroid status (by pattern recognition).