Formation Damage Mitigation in High Pressure High Temperature Gas Field

Summary Viscoelastic surfactants (VESs) have been used for acid diversion and fracturing fluids. VESs were introduced because they are less damaging than polymers. VESs’ high cost, low thermal stability, and incompatibility with several additives (e.g., corrosion inhibitors) limit their use. The goal of this study is to investigate the interaction of VES micelles with different nanoparticle shapes to reduce VES loadings and enhance their thermal stability. This work examined spherical and rod-shaped nanoparticles of silica and iron oxides. The effects of particle size, shape, and surface charge on a zwitterionic VES micellization were conducted. The physical properties were measured using zeta-potential, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The rheological performances of VES solutions were evaluated at 280 and 350°F using a high-pressure/high-temperature rotational rheometer. The proppant-carrying capacity of the fracturing fluids was evaluated using a high-pressure/high-temperature see-through cell and dynamic oscillatory viscometer. The fluid loss and formation damage were determined using corefloods and computed-tomography scans. The interaction between nanoparticles and VES is strongly dependent on the VES concentration, temperature, nanoparticle characteristics, and concentration. The spherical particles at 7-lbm/1,000 gal loading extended the VES-based-fluid thermal stability at VES loading of 4 wt% up to 350°F. The nanorods effectively enhanced and extended the thermal-stability range of the VES system at VES concentration of only 2 wt%. Both particle shapes performed similarly at 4 wt% VES and 280°F. The addition of silica nanorods extended the thermal stability of the 4 wt% VES aqueous fluid, which resulted in an apparent viscosity of 200 cp for 2 hours. The addition of rod-shaped particles enhanced the micelle to micelle entanglement, especially at VES loading of 2 wt%. The use of nanoparticles enhanced the micelle/micelle networking, boosting the fluid-storage modulus and enhancing the proppant-carrying capacity. The addition of nanoparticles to the VES lowered its fluid-loss rate and minimized formation damage caused by VES-fluid invasion. This research gives guidelines to synthesize nanoparticles to accommodate the chemistry of surfactants for higher-temperature applications. It highlights the importance of the selected nanoparticles on the rheological performance of VES.

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Study of Pressurized Fluidized Bed Combustion Combined Cycles With Gas Turbine Topping Cycle

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/92-gt-343 ◽

1992 ◽

Cited By ~ 1

Author(s):

D. Bohn ◽

G. H. Dibelius ◽

R. U. Pitt ◽

R. Faatz ◽

G. Cerri ◽

...

Keyword(s):

High Pressure ◽

High Temperature ◽

Gas Turbine ◽

Energy Input ◽

Fluidized Bed Combustion ◽

High Pressure High Temperature ◽

Combined Cycles ◽

Topping Cycle ◽

Pressurized Fluidized Bed Combustion ◽

High Temperature Gas

Coal based combined cycles for efficient generation of electricity or cogeneration of thermal and mechanical (electrical) power can be realized making use of Pressurized Fluidized Bed Combustion (PFBC). A draw-back with respect to the efficiency, however, is imposed from the combustion system limiting the temperature to some 850°C. This threshold may be overcome by integrating a high pressure, high temperature gas turbine topping cycle into the process. In a first step, the high pressure, high temperature gas turbine is fired by natural gas, and the exhaust gas of the turbine is fed to the PFB combustor as an oxygen carrier. In a future advanced system, the fuel gas may be provided by an integrated coal gasification process. A basic reference case has been established based on commercially available gas turbine equipment, hot gas filtration systems as actually tested in various pilot installations, and on a conservative steam cycle component technology. With an ISO gas turbine inlet temperature of 1165°C and an overall compression ratio of 16 up to 30, the entire process yields a net efficiency of some 46% (LHV) and an overall power output of some 750 MW with the gaseous fuel making up for some 50% of the overall energy input. Both the efficiency and the power output have been found rather insensitive with respect to a variation of the overall compression ratio. However, for a non-intercooled compression, an increase of the maximum process pressure would allow for the energy input to be shifted towards coal (and to reduce the natural gas input), and in particular for an elevated PFB combustor pressure considered mandatory for compactness as well as for combustion efficiency including emissions. The numerous calculations for the design, the optimization and the prediction of part-load operation of complex systems are efficiently performed with a semi-implicit method, the results of which have been checked carefully against those of a more conventional sequential approach and found in good agreement.

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