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Summary Boron-based crosslinkers are used commonly to increase viscosity and to improve fluid-loss control and proppant transportability of guar and its derivative fluids. Boron crosslinkers are usually preferred because of their ability to reheal after shearing and their favorable environmental properties. More-efficient crosslinkers capable of crosslinking fluids with reduced polymer loading have always been of great interest, to reduce both the formation and the proppant-pack damage from polymer residues and to reduce overall fluid cost, especially with the reduced availability and higher cost of guar. Recently, we reported in paper SPE 140817 (Sun and Qu 2011( the synthesis of polyaminoboronates, bulky compounds containing multiple boron sites and capable of interacting with multiple polysaccharide strands to form more complex crosslinking networks at lower polymer loadings than conventional guar fluids. However, to improve the marketability and acceptance of the product, a lower-cost combination of raw materials is sought. In addition, a delaying mechanism to improve the control of the fluid-viscosity buildup can make the product fit into broader applications. A readily available polyamine was used as the base scaffold, and boron was incorporated by means of intermediate borate formed in the condensation reaction between boric acid and ethylene glycol to replace volatile and highly flammable trimethylborate. New chemistry was developed to produce more-controlled crosslinking. The resulting compound exhibited desired adjustable delay characteristics. This paper shows the effect of a series of new crosslinkers in terms of delay properties. The testing results of fluids with a 20%-lower polymer loading, crosslinked with the new crosslinker, are reported and compared with those of conventional fluids. Analysis and discussion of the chemistry, crosslinker performance, and economics are presented.

Most conventional fracturing fluid systems are based on guar and guar derivatives. Therefore, fracturing costs are strongly influenced by guar price. In addition, when pumped in unconventional formations, these fluid systems can cause significant formation damage due to insoluble protein components in guar. While Polyacrylamide (PAM) based copolymers are often used in unconventional formation stimulation, they are often considered to be hard to break. A possible solution that can mitigate the problems associated with the conventional fracturing fluid systems is a new fluid system based on a carefully designed synthetic polymer. The synthetic nature of the polymer translates into a stable operating cost without being impacted by market fluctuations like in the case of guar. This new synthetic polymer system is crosslinked and applied similarly to polysaccharide-based fluids. To alleviate concerns that synthetic polymer is hard to break, this polymer incorporates special linkages, periodically distributed along its backbone, to make it easily broken into small fragments with conventional oxidative breakers under downhole conditions to leave minimal formation or fracture damage. The polymer also incorporates functional groups that resist damage from water hardness. In addition, the polymer hydrates almost instantaneously and allows rapid viscosity generation and adjustment without a hydration unit, which greatly reduces footprint of hydraulic fracturing treatments. While this new polymer system can be used in slickwater hydraulic fracturing and linear gel applications, laboratory testing also showed that it can be effectively crosslinked with conventional metal crosslinkers. This paper investigates the possibility of using this new polymer as a total package to be applied throughout hybrid fracturing operations for tight formations besides using it as fracturing fluids for conventional formations. Laboratory work also investigated other applications of the new polymer such as acid gelling, acid fracturing, and diversion, to name a few. This paper presents the laboratory performance and the underlying mechanisms of the novel polymer fluid system.

Oilfield produced water often contains high levels of total dissolved solids (TDS) in addition to precipitates, suspended particles, and hydrocarbons. The main components of the dissolved solids include sodium, calcium, and magnesium salts. The combination of the high salinity and high hardness in produced water can be very damaging to many types of fracturing fluids that are commonly formulated with fresh and clean water. It is usually costly to treat high-TDS produced water to such an extent that it can be safely and stably used to formulate fracturing fluids. Meanwhile, it is also expensive to dispose of produced water by underground deep well injection or to transport produced water for disposal at a commercial oilfield wastewater disposal facility. On the other hand, fresh water for formulating fracturing fluids is becoming more costly and more difficult to obtain in many oil/gas production areas. Fluid systems have therefore been highly desirable and sought after that can be formulated directly with high-TDS water and perform well at high temperature of 275 °F or above. A group of fracturing fluids was successfully identified recently that performed very well at high temperatures when formulated with untreated high-TDS produced water. The produced water tested had TDS up to about 330k mg/L and hardness (calcium carbonate equivalent) up to about 64k mg/L. The fracturing fluids comprised of organometallic-crosslinked derivatized polysaccharides. In one typical example, the viscosity stayed above 100 cP (at 100/s shear rate) for about 80 minutes at 275 °F recorded for a fracturing fluid prepared with untreated produced water with TDS of about 300k mg/L and hardness of about 50k mg/L. The magnitude and lifetime of the fluid viscosity were dependent on a number of factors such as the produced water TDS and hardness, test temperature, polymer loading, fluid pH, etc. The fracturing fluids also showed minimum damage to the formation or proppant pack tested. In a typical proppant pack conductivity test at 250°F, the retained conductivity was about 90% for the fracturing fluid mixed with appropriate amount of oxidative breaker. The outstanding performances and the underlying mechanisms of the high-temperature fracturing fluids prepared with untreated extremely high-TDS and hard produced water will be discussed, and the field-related laboratory test results will be presented.

Post-treatment production analyses after hydraulic fracturing with crosslinked gel or slickwater often indicate that the treatment did not achieve the designed fractured area, which could be attributed to non-ideal proppant placement in the fracture. Although crosslinked gel provides good proppant suspension, it may not provide the desired proppant transport under downhole conditions. It is also difficult to clean up and thus induces gel damage into the proppant pack and formation. Slickwater treatment reduces gel damage, but proppant settling and banking problems can reduce the chance of achieving optimal fracture conductivity. Several proppant placement techniques have been developed to generate highly conductive paths for hydrocarbons to flow from an unconventional reservoir to the wellbore, such as hybrid fracturing, ultralightweight proppant delivery, and reverse hybrid fracturing. This paper demonstrates a novel fracturing fluid and its nearly perfect proppant transport characteristics. An engineered method of applying such fluids to optimize proppant placement and maximize fracture conductivity is discussed. The novel fracturing fluids are based on preformed gel fluids. When properly selected, the fluids can ideally suspend proppant under downhole conditions and carry all types of proppants into the fracture. This leads to better transverse and vertical placement of proppant in the fracture and significantly increases the fractured surface area, which is one of most important factors in unconventional reservoir production. The degradability of the fluid can be controlled by reservoir temperature, fluid pH, or breaker loading, which leads to optimized proppant pack conductivity. This paper discusses the evolution of the technology and laboratory testing results for this unique fluid system. The system has applications in areas requiring high fractured surface area and high regained conductivity, such as unconventional liquids-rich formations.

Simulation-based resuscitation education has emerged as a key to improving patient safety and numerous healthcare organisations have invested in high-fidelity simulation training centres. However, the high purchasing cost, limited portability, technical expertise and organisational skills required to coordinate these high-fidelity simulation centres are factors that limit their use as a wide-spread teaching and learning method. Creative innovation is required. The aim of this study was to pilot an inexpensive, portable, novel high fidelity humanistic simulation modality, for educating nurses and doctors in recognising and responding to the deteriorating patient. Analysis of five focus group discussions revealed the main theme of engagement in the simulation experience with three main subthemes of realism of the character, believability of the experience and being more connected. In conclusion, this innovative simulation modality offers a viable alternative for resuscitation training.

Over a period of two years, 40,000 newborn infants in South Australia have been screened for congenital hypothyroidism by the measurement of thyroxine and, on selected samples, of thyroid stimulating hormone. Samples were those obtained for an established newborn screening programme in the State. Eight infants with hypothyroidism were detected; in seven, this was due to congenital agenesis of the thyroid gland and one infant had residual thyroid tissue. A further three sick infants had abnormalities of thyroid function; in two, this was transient and reverted to normal after several weeks and the third infant died. Three infants had thyroxine-binding globulin deficiency.