Study of produced water using hydrochemistry and multivariate statistics in different production zones of mature fields in the Potiguar Basin – Brazil

• The largest amount of water is being produced in oil wells of mature fields.
• We investigate some chemical parameters in produced water from oil extraction.
• We obtain well samples of six different production zones.
• Hydrochemistry and statistical analysis are used to characterize the reservoir zone.
• The discriminant function developed estimates the production of water in each zone.

The extraction of oil in onshore and offshore deposits produces aqueous waste, called produced water. Global production of produced water has increased in the last decade and continues to rise. When a well which produces by more than one production zone starts to produce with excessive basic sediment and water (BSW), it is necessary to make an intervention on it to isolate the zone with high water production. This study applies multivariate statistics (linear discriminant analysis) to develop a methodology to classify different oil production zones from some chemical parameters of water produced. The water samples were collected from mature fields wells that produce oil from a single zone, in the Potiguar Basin (Brazil). We obtain discriminant functions that distinguish chemically the different production zones studied in this study. Although in this work has used chemical parameters of each production zone studied (100, 160, 240, 260, 300 and 400) to obtain the discriminant functions, we believe it can be used in wells with high BSW that produced with more than zone reservoir because the ion concentration is of the zone that produces water more than others.