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von Gunten, Konstantin (University of Alberta) | Snihur, Katherine N. (University of Alberta) | McKay, Ryan T. (University of Alberta) | Serpe, Michael (University of Alberta) | Kenney, Janice P. L. (MacEwan University) | Alessi, Daniel S. (University of Alberta)
Summary Partially hydrolyzed polyacrylamide (PHPA) friction reducer was investigated in produced water from hydraulically fractured wells in the Duvernay and Montney Formations of western Canada. Produced water from systems that used nonencapsulated breaker had little residual solids (<0.3 g/L) and high degrees of hydrolysis, as shown by Fourier-transform infrared (FTIR) spectroscopy. Where an encapsulated breaker was used, more colloidal solids (1.1–2.2 g/L) were found with lower degrees of hydrolysis. In this system, the molecular weight (MW) of polymers was investigated, which decreased to <2% of the original weight within 1 hour of flowback. This was accompanied by slow hydrolysis and an increase in methine over methylene groups. Increased polymer-fragment concentrations were found to be correlated with a higher abundance of metal-carrying colloidal phases. This can lead to problems such as higher heavy-metal mobility in the case of produced-water spills and can cause membrane fouling during produced-water recycling and reuse.
Grimaldi, Maurício Carvalhinho (TRANSPETRO) | Castrisana, Walterli José (TRANSPETRO) | Tolfo, Fabiano Coradini (TRANSPETRO) | Christino, Fernando Protti (Petrobras) | Geraldo, Lúcia Maria (Petrobras) | Saliba, Gustavo Coutinho (Petrobras) | Lopes, Daniela Emilia (Petrobras)
Abstract Produced water is highly saline. It may be used for soda ash (sodium carbonate) production. That is why its main component is sodium chloride and soda ash industrial process is based in brines. This process, in use since 1861, is also known as Solvay process. It starts when seawater-based brines receive ammonia gas, making up ammoniated brine. In the following step, carbon dioxide is added, precipitating sodium bicarbonate, which is filtered, leaving an ammonium chloride solution. Sodium bicarbonate is pyrolised to soda ash, water and carbon dioxide, which returns to the carbonation step. Produced water will undergo a pre-treatment step designed for removing metals such as calcium, magnesium and iron. After this procedure, produced water will be evaporated until it reaches the brine concentration for Solvay process. This operation also produces high purity water, suitable for many purposes. Carbon dioxide (CO2) used in this process is originally obtained from thermal decomposition of limestone. Soda ash is an important raw material for a wide variety of products, such as glass, soap, cosmetics, etc. Brazil imports all soda ash used by its industries. Using high salinity produced water for producing it may be a very attractive alternative with huge economic and environmental incomes. It may be possible to use CO2 captured from atmospheric emissions, contributing to mitigate global warming. Some laboratory scale experiments are in course now, dealing with Solvay process applied to produced water conversion into soda ash. Present results have shown that the process is feasible, allowing us to scale it up to a pilot scale. Considering the environmental benefits obtained of this process, both in wastewater treatment and carbon sequestration, as well as the production of a valuable commodity, applying Solvay process for treating produced water is a promising technology for the next years.
Abstract Within 1st of March 2000 all operators on the Norwegian Shelf were required to present zero harmful discharge strategies for each individual oil/gas field. This paper present presents the status of SEPNos (A/S Norske Shell E&P) implementation of a zero harmful discharge strategy for the Draugen field at the Norwegian Continental Shelf, following the requirements from the Norwegian environmental authorities (SFT). It describes the achievements so far related to produced water, sea water injection and drilling operations and our further plans/feasibility studies. The zero harmful discharge strategy is incorporated in SEPNos environmental management process for Draugen and is integrated in the companys HSE Objectieves and Strategies. The integration philosophy will probably result in an extra drive and synergistic effects between EMAS/ISO 14000, the Norwegian regulations and the zero discharge strategy Introduction The Draugen Field The Draugen field is operated by SEPNo (A/S Norske Shell, Exploration & Production). The platform is located at 251 m waterdepth at Haltenbanken, on the Norwegian Continental Shelf. The oil production started in October 1993 and is predicted to continue until year 2016. Produced water from the field is expected to rapidly increase within the next 1–3 years. At present the oil production is approx 220.000 bbls/day. Draugen has six producing platform wells, two producing satellite wells, one gas injection well, and five seawater injection wells. Two additional wells were drillied in 2001 in the Garn West area located southwest of Draugen. The oil from Garn West will be transported for further processing at Draugen. The oil is stored in the storage cells of the platform and is transported from Draugen in tankers loading the oil at a FLP loading buoy. The associated gas from the field is transported via the Draugen Gas Transport pipeline through the Åsgard Transport Pipeline to Kårstø. Draugen was EMAS (Eco- Management and Audit Scheme) approved in May 1999. The same year SEPNo was ISO 14001 certified as well. The first EMAS recertification of Draugen took place in June 2000 and the next recertification will take place in 2003. Background The White Paper Environmental Policy for a Sustainable Development (1996–97) from the Norwegian Ministry of Environment defined a zero discharge goal for the offshore activities on the Norwegian Continental shelf. The goal is required to be fulfilled within 2005. In 1997/1998 a project was initiated to define what zero discharge meant in practice for the Norwegian offshore industry. Oil companies, suppliers and the Norwegian authorities participated in this joint effort. The project concluded that the aim should be to reduce the environmental impact, by reducing the discharges of harmful substances, either naturally occurring eg aromatics, heavy metals and PAHs in produced water, or man-made harmful chemicals eg. process chemicals, drilling fluids. Measures resulting in increased pollution from other sources eg transport of waste to shore, increased energy demand resulting increased air emissions should be subject of special consideration. The Draugen Field The Draugen field is operated by SEPNo (A/S Norske Shell, Exploration & Production). The platform is located at 251 m waterdepth at Haltenbanken, on the Norwegian Continental Shelf. The oil production started in October 1993 and is predicted to continue until year 2016. Produced water from the field is expected to rapidly increase within the next 1–3 years. At present the oil production is approx 220.000 bbls/day. Draugen has six producing platform wells, two producing satellite wells, one gas injection well, and five seawater injection wells. Two additional wells were drillied in 2001 in the Garn West area located southwest of Draugen. The oil from Garn West will be transported for further processing at Draugen. The oil is stored in the storage cells of the platform and is transported from Draugen in tankers loading the oil at a FLP loading buoy. The associated gas from the field is transported via the Draugen Gas Transport pipeline through the Åsgard Transport Pipeline to Kårstø. Draugen was EMAS (Eco- Management and Audit Scheme) approved in May 1999. The same year SEPNo was ISO 14001 certified as well. The first EMAS recertification of Draugen took place in June 2000 and the next recertification will take place in 2003.
Abstract The minimization of polymeric damage is an important factor to the conductivity and productivity of a well. In many cases this damage is attributed to unbroken gel residue and/or dynamically formed filter cake on the formation faces. Recently, removal treatments have been developed and improved for the polymeric damage resulting from fracturing, gravel packing, drilling and workover operations. The best method, from a chemical standpoint, of monitoring the extent of polymer damage and its subsequent degradation is through the examination of flowback samples. Flowback analysis provides valuable information regarding well cleanup progress at various intervals and may be used as a quantitative profile for the amount of polymer treatment load recovered. Samples are analyzed before and after treatments to determine the total carbohydrate content, which is a gauge of polymeric damage produced by guar, cellulose, starch, xanthan and other polysaccharides. Although high carbohydrate levels are a symptom of damaged wells, it is misleading to conclude that lower carbohydrate content equates to a lesser degree of damage. Other factors, such as bacterial presence, enzyme activity and size distribution of polymer fragments contribute significantly to the results of flowback analysis. This paper presents an improved method to effectively analyze flowback samples as well as a guideline for applying these new procedures. Detailed laboratory protocols are presented that include tests for carbohydrate content, molecular weight distribution, enzyme/bacteria detection and viscosity measurements. This improved flowback analysis provides a method to detect polymer damage downhole and may be used to evaluate polymer load recovery. Several field studies are also included to demonstrate this new comprehensive procedure. Introduction Produced waters have long been recognized as an important source of information about reservoirs. Oil field waters are analyzed for various physical and chemical properties including pH, specific gravity, content of iron, bicarbonate, chloride, sulfate and other inorganic anions and cations. The characteristics of produced waters from several typical wells are presented in Table 1. Chemical analysis of formation waters is useful in production problems, such as identifying the source of intrusive water, planning waterflood and saltwater disposal projects and treating to prevent corrosion problems in primary, secondary and tertiary recovery. An previous method of quantifying cleanup following the fracturing of a well was to report load water recovery. Chlorides, sulfates and/or specific gravity of the flowback were tested and compared with properties of the formation water. These methods attempted to quantify fracture load recovery, but was only a measure of the water load and gave no information about polymer return. Natural, water soluble polymers have a long history of use in oil field applications due to their unique fluid rheology characteristics, proppant carrying ability and high temperature stability. Applications include drilling, fracturing, enhanced recovery, completion and workover operations. However, the fact that these same polymers can leave behind unbroken gel filter cake and insoluble residues has been well established. Polymer filter cake is deposited on formation faces or within the fracture during pumping and/or upon fracture closure. At times the concentration of the filter cake becomes so high that breaker additives are unable to thoroughly degrade it. Insoluble residues and high molecular weight fragments are polymer degradation products that are no longer soluble and, therefore, fall out of solution. These degradation products can settle within the proppant pack and impair permeability. Since the damage produced by natural polymers can have a negative effect on well productivity, it is important to ensure that most of the polymer is returned after a treatment. Flowback waters are now being recognized as a valuable source of information regarding polymer damage. Pope reported that a more quantifiable approach to describing fracture cleanup is performed by determining the amount of guar returned from the fracture during flowback. Brannon/Tjon-Joe-Pin and Tyssee/Vetter also used analysis of return waters to support arguments made by their studies regarding polymers. This paper presents an improved method to effectively analyze flowback samples for polymeric damage. P. 485^