Fractured reservoir analysis using modern geophysical well techniques: application to basement reservoirs in Vietnam
S. M. Luthi, 2005. "Fractured reservoir analysis using modern geophysical well techniques: application to basement reservoirs in Vietnam", Petrophysical Properties of Crystalline Rocks, P. K. Harvey, T. S. Brewer, P. A. Pezard, V. A. Petrov
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Recent geophysical well techniques have significantly improved the analysis of fractured reservoirs. These methods include electrical and ultrasonic scans and, in some cases, optical video images, that provide azimuthal high-resolution images of the borehole wall on which fractures are prominently visible. Additionally, fractures produce reflections and attenuations of the Stoneley wave, a borehole mode recorded by the array sonic wireline tool. A fracture identified with these methods can be individually probed with a new wireline formation tester featuring a dual-packer module that hydraulically isolates it from the surrounding formation. The combination of these techniques can provide information on fracture locations, dip, azimuth, aperture, permeability and fluid content. Seismic data can be used to extrapolate this information away from the wells. A case study on basement reservoirs from offshore Vietnam exhibits foliations, borehole breakouts, hydraulic and tectonic fracturing. Oil production comes from a small number of point entries that correspond to fractures, most of which produce more than 1000 barrels of oil per day. Two intersecting fracture sets were found, which may explain the high sustained production. Properly planned horizontal wells may increase production and decrease the chance of water breakthrough.
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Boreholes are commonly drilled into crystalline rocks to evaluate their suitability for various applications such as waste disposal (including nuclear waste), geothermal energy, hydrology, sequestration of greenhouse gases and for fault analysis. Crystalline rocks include igneous, metamorphic and even some sedimentary rocks. The quantification and understanding of individual rock masses requires extensive modelling and an analysis of various physical and chemical parameters. This volume covers the following aspects of the petrophysical properties of crystalline rocks: fracturing and deformation, oceanic basement studies, permeability and hydrology, and laboratorybased studies. With the growing demands for sustainable and environmentally effective development of the subsurface, the petrophysics of crystalline rocks is becoming an increasingly important field.