PRE AND POST-SWELLING MECHANICAL BEHAVIOR OF A WATER-SWELLING ELASTOMER
Swelling elastomers are a very recent development in the world of advanced polymers, and are being successfully used in the form of packers and other sealing elements in various oilfields. Improved design of sealing elements and prediction of seal performance under different well conditions require a good knowledge of mechanical response of the swelling elastomer. This study reports results of hardness and tensile testing carried out on disc and ring samples of a water-swelling elastomer. Material properties of the elastomer were measured before swelling and periodically after swelling for a total testing time of 15 weeks, under water salinities of 0.6%, 12%, and 25%, and temperatures of 25°C, 50°C, 80°C, and 97°C. Reported results can be used by oilfield engineers as prequalification of the elastomer for downhole applications, and by designers using numerical simulations for improvement of elastomer-based sealing and packer design.
Mechanical Testing and Characterization of a Swelling Elastomer
Elastomers are being increasingly used for sealing and other applications in the oil and gas industry. Specifically developed elastomers possess durable properties and have the ability to withstand detrimental effects of heat, chemicals, and harsh environments. For successful modeling and simulation of various downhole processes, it is very important to determine the behavior of elastomer materials under realistic well conditions. Of special interest is the class known as swelling elastomers. This article reports some results from experiments conducted on mechanical testing and characterization of an inert (nonswelling) and a water-swelling elastomer (both belonging to the EPDM family) used for sealing purposes by a local petroleum development firm. Experiments were designed and conducted in accordance with standard ASTM test methods. Apart from regularly available testing equipment, some simple test rigs and fixtures were designed and fabricated. Elastomer behavior was tested for hardness, compression set (at different temperatures and for different periods of time), tensile set (for different periods of time), tensile properties (fracture strength and percent elongation), and swelling. In the swelling test, different sample geometries (unconfined samples and samples mounted on steel plate) were tested for a total duration of 1000 h (roughly 45 days) in salt solutions of different concentrations and at different temperatures. Results show that compression set increases with increasing temperature and testing time, while room temperature tensile set also increases with longer testing time. Compared to the inert elastomer (exhibiting nonlinear elastic behavior like normal rubbers), swelling elastomer surprisingly showed linear stress—strain response. As expected, the inert elastomer did not exhibit any change in volume, while the swelling elastomer showed significant volume/thickness increase with increasing test temperature and decreasing salt concentration.
Evaluation of CuAl2O4 as an Oxygen Carrier in Chemical-Looping Combustion
The chemical-looping combustion (CLC) process is a novel solution for efficient combustion with intrinsic separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor where the fuel, or gasification products of the fuel, reacts with the solid oxygen carrier. In this work, copper(II) aluminate (CuAl2O4) was assessed as a potential oxygen carrier using methane as fuel. The carrier particles were produced by freeze–granulation and calcined at 1050 °C for a duration of 6 h. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900–950 °C during 45 alternating redox cycles. The oxygen carrier exhibited reproducible and stable reactivity behavior in this temperature range. Neither agglomeration nor defluidization was noticed in any of the cycles carried out at 900–925 °C. However, after reactivity tests at 950 °C, soft agglomeration and particle fragmentation were observed. Systematic phase analysis of the Cu–Al–O system during the redox cycle was carried out as a function of duration of reduction and oxygen concentration during the oxidation period. It was found that the CuAl2O4 is reduced to copper(I) aluminate (CuAlO2; delafossite), Cu2O, and elemental Cu. The CuAlO2 phase is characterized by slow kinetics for oxidation into CuO and CuAl2O4. Despite this kinetic limitation, complete conversion of methane with reproducible reactivity of the oxygen carrier is achieved. Thus, CuAl2O4 could be a potential oxygen carrier for chemical-looping combustion.