Components of Produced Water: A Compilation of Industry Studies

Abstract

Summary Produced water contains many different constituents. Each has a different impact on the environment when present in discharged water. All these components have been studied at various times and for diverse reasons by several organizations. These studies, which cover dispersed and soluble oil, radionuclides, production chemicals, and heavy metals, are brought together here production chemicals, and heavy metals, are brought together here along with new data to present a complete picture of produced water. Many constituents of produced water have no known environmental effects, while others have only minor effects. In general, produced water is not harmful in the offshore environment where produced water is not harmful in the offshore environment where more than adequate dilution occurs. Introduction Produced water is the largest waste-stream source in the entire Produced water is the largest waste-stream source in the entire E and P process. Over the economic lift: of a producing field, the volume of produced water can be more than 10 times the volume of hydrocarbon produced. With volumes of this magnitude, the disposal of produced water becomes very important to the operator and the environment. The preferred disposal method for produced water is the one that adequately protects the environment at the lowest cost to the operator. Regulatory constraints often limit the options of the operator to methods that may not be necessary for environmental protection. In many onshore areas of the world, produced water is injected into underground formations that contain water unsuitable for human consumption. In other onshore areas, in many wetlands, and offshore, produced water is discharged to the environment. The discharge of such large volumes of waste into the environment has caused concerns about uncontrolled, irreversible, and dreadful pollution in both government agencies and nongovernment organizations. pollution in both government agencies and nongovernment organizations. The basic source of these concerns is a lack of knowledge about the constituents of produced water and their effects. The basic components of produced water can be grouped into the following main categories: oil, heavy metals, radionuclides, treating chemicals, salt, and dissolved oxygen. Oil Oil is the common term applied to organic material that is dispersed or dissolved in produced water at the time of discharge. Dispersed oil consists of small discrete droplets suspended in the water while dissolved or soluble oil is present in the dissolved form. All oilfield water-treating equipment in use today is designed to remove these droplets from the water under Stokes' law. These devices operate by taking advantage of the difference in density between oil droplets and water. In addition to density, the other main parameter of concern in this separation is the size of the oil droplet. According to Stokes' law, the velocity at which the oil droplet rises through the water also varies directly with the square of the droplet diameter.