Water Analysis Data: Interpretation and Applications

The value of water analysis data in petroleum exploration and production iswidely recognized. Water analyses have proven useful in water productionproblems, in the correlation of stratigraphic units and of the aquifers withinthese units, and in the study of the movement of subsurface waters. A large volume of water analysis data is available for the Western Canada Sedimentary Basin. Maximum benefits may be derived from these data through thecareful selection of analyses that represent most accurately the chemicalcomposition of the subsurface waters. Various graphical methods have been devised for presenting the chemicalanalysis of a water. Graphical diagrams are particularly useful in comparingwater analyses. Isoconcentration maps provide information essential for the study of thechemical and physical behaviour of formation waters. Furthermore, these mapsprovide information that can be converted readily to water resistivitydata. Studies of the chemistry of formation waters, carried out in conjunctionwith studies of the geologic framework wherein the waters reside, can be mosteffective in the solution of local and regional problems. Introduction Subsurface water is a generally unwanted commodity found during the searchfor, and exploitation of, oil and gas reserves. Because subsurface water oftencontains a large amount of dissolved salts, it is unsuitable for domesticpurposes. By virtue of the dissolved salts and of certain gases held insolution, this water is a powerful chemical agent capable of corroding themetal in well equipment. Yet the very presence of these salts and gases makeswater analysis useful in certain exploration and production problems. In addition to discussing the interpretation and applications of wateranalysis data, this paper discusses sampling procedure and analyticaltechniques. Proper campling and analytical methods are requisites to obtainingmaximum information on subsurface waters. This means ensuring that the samplesclosely represent the formation waters and that the chemical analyses provideadequate data for both present and future requirements.