Volatile and semi-volatile organic compound patterns in flowback waters from fracturing sites within the Marcellus Shale

摘要

Gas shale fracturing relies on a method known as horizontal fracturing to remove gas trapped within the impermeable facies. Conventional vertical and unconventional horizontal fracturing requires a large amount of water to be injected downhole under high pressure. These fracturing fluids can contain high concentrations of petroleum hydrocarbons with known adverse health effects. The development of reuse technologies that reduce the need of potable water requires an accurate understanding of petroleum hydrocarbon loading during key points in the fracturing process. In this study, flowback water quality from both horizontally and vertically fractured wells within the Marcellus Shale region in Pennsylvania and West Virginia were analyzed. Flowback data made available by the Shale Network were collected using geographic information systems. Flowback sample analytes of interest were diesel range organic (DRO) and gasoline range organic (GRO) compounds. Noticeable patterns were present in DRO and GRO flowback data. Flowback water results showed differences between horizontally and vertically fractured well DRO patterns. Vertically fractured wells showed a sharp decrease in DRO concentrations following fracture events. Horizontally fractured wells exhibited a peak in loading when flowback water shifted to produced water. This pattern suggests the method of completion may affect DRO loading. GRO loadings appeared to not be effected by the method of completion. A horizontally fractured well and vertically fractured well within 16 km showed similar loading patterns. GRO data suggest factors such as geographic location may be responsible for VOC loading trends.