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Abstract Shale gas development relies heavily on multi-stage hydraulic fracturing (HF) to maximize the economic viability of each new well. Industry is making a concerted effort both to recycle and re-use produced brine from fracturing operations and to use alternate water sources for well operations. Some experts foresee almost all produced brines being treated and reused within the next five years. Texas A&M Global Petroleum Research Institute (GPRI) has been one of the leaders in promoting new technology to reach these goals. In the past decade we have conducted a number of field trials in different shale plays to a) identify technologies and determine their effectiveness, b) field test advanced monitoring and measurement techniques, and c) integrate the technologies into one cost-effective program for the industry. This paper presents results from these trials that compare different types of filtration media used to remove hydrocarbons, filtration techniques to remove suspended solids and nano filtration materials to stabilize ultrahigh salinity brines making them compatible with today's fracturing fluid designs. In addition to describing cost effective brine treatment, we have provided a venue for testing advanced analytical techniques that provide rapid ways to measure the effectiveness of such water treatment. Measuring hydrocarbon content in the brines aids in selection of optimal treatment and monitoring of its effectiveness. New fluid imaging techniques characterize particulates in brines and can help to optimize filtration requirements. Biological monitoring can determine effectiveness of solids removal practices and helps in selection of appropriate bacterial control. This paper will discuss the need to utilize on-site, real-time analysis of produced water and frac flow back brine to allow faster and more accurate characterization of the oil and gas waters being cycled back to unconventional gas development. The benefits of the technology come from improved procedures to characterize and mitigate the risks of HF at drilling and hydraulic fracturing sites. Better monitoring and treatment can help to counter the mounting concerns of legislators, regulatory agencies, and the general public as well as aid the economic development of our natural gas resources.
Abstract The ultimate goal of produced water management is to remove dissolved components and use the desalinated water for beneficial uses that can effectively alleviate environmental impact and water shortage. Presently, many of the efforts have been focused on membrane technologies including reverse osmosis and electrodialysis. Unfortunately, no large scale implication of produced water desalination by membranes has been reported. The main obstacle against the deployment of desalination technologies for produced water purification has always been the complicated chemical composition and associated high operating cost. Membrane technologies are generally believed to be energy efficient due to single-phase operation comparing to thermal-based desalinations. However, the presence of dissolved organics and scale deposition on membrane surfaces require sophisticated pretreatment and frequent membrane replacement, adding to the water treatment costs. Reverse osmosis membranes including polymeric membranes and molecular sieve zeolite membranes were investigated for ion removal from produced water by a cross-flow RO process. Considerable flux decline with elapsed operation time was observed from 11.5 to 6.8 L/m2.h at a transmembrane pressure of 3.5 Mpa. Pretreatments including nanofiltration and adsorption by active carbon were studied for their influence on the RO performance and impact on the overall desalination cost. Both polymeric membranes and molecular sieve zeolite membranes have been tested for actual produced water from oilfield and coalbed methane site. The study has revealed that (1) most of permeation tests lasted less than 3 months due to serious fouling and drastic flux decline (>30%), (2) scale precipitation and organic sorption are the major fouling mechanisms of membranes, (2) multistage pretreatment is crucial to extend membrane lifetime, and (3) nanofiltration is the only effective process tested that can extend the life of a RO membrane to over 6 months. But periodic chemical cleaning, typically twice a week, is necessary to maintain the desired water flux. The economical efficiency of these processes was discussed from the aspects of produced water chemistry, energy consumption, and water treatment capacity. Considering small to mid-sized water treatment capacity (50 m3/day), the cost of produced water desalination by RO membranes is around $3.7/m3 including nanofiltration pretreatment. Pretreatment and membrane replacement are the major factors that increases the operation cost and limits the economic efficiency of membrane technology for produced water desalination.
Abstract Shale gas development relies heavily on multi-stage hydraulic fracturing to maximize the economic viability of each new well. In recent years, the industry is aiming at re-use of frac flow back brine to reduce costs and environmental impact of operations. The challenge is to identify technologies and approaches for treating the frac water that returns to the surface following a frac job (frac flowback water) for beneficial re-use in other applications, thereby conserving other local freshwater supplies. Field trials in upstate New York have been conducted to test new technology to treat brines characteristic of flow back brines from the Marcellus Shale and make them amenable for re-use in subsequent oil field operations. The Texas A&M GPRI produced water treatment program began in the year 2000. In the past decade we have shown that produced water and frac flowback brine from shale gas and tight gas well drilling operations can be treated and reused instead of tapping in to additional fresh water resources. Now the program is working to demonstrate that low cost, mobile units can be deployed in field operations to replace the more costly and environmentally questionable practices currently being employed in field operations. This report describes the field trial in Chenango County New York conducted by the Texas A&M Desalination Program during the 3 quarter of the year 2011. The specific goal of the field trial was to develop and utilize a mobile unit to demonstrate the effectiveness of different membrane technology suitable for use with high salinity flow back brines and produced water from the Herkimer formation the brines deemed the equivalent of Marcellus Shale brine. The several treatment techniques which have been found to be successful in both pilot plant and field tests have been tested to incorporate into a single multifunctional process train. Eight different components were evaluated during the trials, two types of oil and grease removal, one BTEX removal step, three micro-filters, and two different nanofilters. The performance of each technique was measured by its separation efficiency, power consumption, and ability to withstand fouling overall, the field trial was a success. Of the four field brines evaluated, three were treated with minimal problem. Over 6,000 gallons of brine were processed. Total power cost was approximately $1.00 per barrel of fluid treated.
Abstract Large quantities of seawater are injected in oil and gas fields for pressure support and sweeping efficiency of the reservoir. This injection enhances the hydrocarbon recovery. Many difficulties are induced by sea water injection, such as the risk of sulfate based scale formation like barium sulfate precipitation. Seawater contains around 2800 mg/L of sulfate and some reservoir water may contain large quantities of barium and strontium. When those two waters are mixed into the reservoir, precipitation will occur and reduce the efficiency of water injection. In the producer wells, scale deposits may significantly reduce oil production. This is why technical solutions are more and more implemented to remove sulfate from the sea water before injection. Filtration processes using nanofiltration membranes are able to reduce the sulfate content of seawater, and this technique has been successfully operated for more than 12 years on several TOTAL offshore sites. The use of nanofiltration membranes requires an efficient pretreatment of seawater in order to control the fouling that will reduce the capacity of the sulfate removal unit over time. The only way to remove this fouling and recover the capacity of the unit is to stop a part of the unit and operate a chemical cleaning of the membranes. Biological fouling appears to be predominant on nanofiltration membranes for this application. As a consequence, preventing biofilm growth is a key aspect to increase availability of those units and can also be of interest for corrosion management. This paper presents the main results of experiments carried out by TOTAL on a sea water filtration pilot. Biofilm measuring probes have been tested in order to detect as soon as possible a change in the growth rate of the biofilm. Results demonstrated that such tools could be implemented in order to detect a default in the biofilm prevention strategy. This early detection tool will enable to react before the full system (all trains) requires a chemical cleaning in place. The eventual objectives of this tool are to maximize reliability of desulfated water injection, to optimize use of chemicals, to increase nanofiltration membrane lifetime, and facilitate field operation of such units.