An ion–salt complex of rocks from the Bazhenov formation of West Siberia

Abstract

The results of experimental studies on the macro- and microcomponent composition of the ion–salt complex of argillaceous siliceous rocks from the Bazhenov formation of West Siberia are presented. The studies were based on the analysis of samples using a high-resolution mass spectrometer with ionization in inductively coupled plasma, by the X-ray diffraction (XRD) method, and via the study of water and ammonium extracts from samples with a natural moisture content, as well as after drying. It was established that the composition of the solutions of water extracts from rocks with a natural moisture content belongs to the sulfate- sodium-bicarbonate type with increased content of dissolved silicic acid with weakly alkaline pH values (∼9.5) and is considerably different from the content of water extracts from the samples after drying. Sodium dominates in the exchange complex; the cation exchange capacity is 14–19 mg-eq/100 g of rock. A sharp excess of the percentage abundance by 2–10 orders of magnitude was recorded for barium, boron, zinc, vanadium, uranium, and arsenic. The barium content in pore water exceeds the strontium content by a factor of 10, which is anomalous with respect to the reservoir formation waters in the majority of oil fields and to the ocean water.