Chemical and physicochemical properties of formation waters of the oil and gas industry

Current concerns and discussions regarding hydraulic fracturing and other activities of the oil and gas industry and geothermal energy sector are forcing a reassessment of formation waters as well as their impacts on the environment. In this review paper, the chemical and the most important physicochemical properties of low- to high-salinity formation waters are analysed and critically evaluated. Especially the complex interactions of the dissolved salts, the isotonicity and the relevance of the pH of virgin formation waters are discussed in this context for the first time. These "by-products" of the oil and gas industry are presented in a new light, whereby a clear distinction made between live and dead formation waters. Due to this significant differentiation, most research results of the past must be critically assessed and reclassified. With the highlighted importance of the composition of formation and injection waters, the most common causes for early termination of the production phases, the possible long-term damages to reservoirs and the origin of man-made earthquakes are described. Treatment concepts for dead formation/process waters, as well as conclusions regarding an environmentally friendly management thereof, are mentioned.