Produced water quality characterization and prediction for Wattenberg field

2013 Spring.Includes bibliographical references.Produced water is the major Exploration & Production waste in oil and gas production operations on most onshore and offshore platforms. There are some concerns about the environmental impacts of produced water, because of the potential danger of large volume of water disposal by shale plays. It is a complex mixture of dissolved and particulate inorganic and organic matters ranging from near freshwater quality to concentrated saline brine. The most abundant inorganic chemicals are calcium, magnesium, sodium and chloride. Other inorganic components, such as barium, strontium, boron, sulfate, carbonate and bicarbonate are also present in the produced water but at high concentrations. The dominant organic chemicals in most produced water are soluble low molecular weight organic acids and some aromatic hydrocarbons. Constituents of produced water vary a lot depending on a number of factors, including geographic locations, characteristics of formations (i.e. the depth of formation, porosity and permeability of formation rocks/sands, water content) and injected fracturing fluid. Since water is becoming a big issue in some arid areas and as regulations become more restrictive for disposal and reinjection, produced water reuse/recycle will be a solution to reduce the wastewater production and alleviate environmental effects. The main objective of this study was to statistically evaluate the produced water quality and to provide an assessment on the spatial distribution of specific groundwater quality parameters. Produced water samples were collected at 80 sample points (producing oil and gas wells) from May to August in 2012. pH, conductivity, alkalinity, turbidity, total organic carbon, total nitrogen, and barium were tested at Colorado State University's Environmental Engineering lab; total dissolved solids (TDS), calcium, magnesium, sodium, potassium, strontium, boron, chloride and sulfate were measured in ACZ Laboratories Inc., Colorado. All the produced water samples were acidic with pH ranging from 5.1-6.8. TDS, cations, anions and organic carbons tested in our study varied a lot. Maps showing the spatial distributions of these parameters were made using ArcGIS. Linear correlations between chloride, conductivity/TDS, and cations (log) were shown, which made it possible to estimate unknown parameters. Spatial and temporal trends of pH, TDS and total organics together with inner relationships of ion concentrations could allow us to make predictions of produced water qualities. This project was the first phase of the development of a GIS application that will provide a tool that can benefit industry when making decisions regarding produced water recycling