科研之友
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摘要
A uniaxial compression apparatus designed to investigate the dynamics of proppant particle packing is described. This dynamic compression device (DCD) uses a small charge of particles, approximately 3.5-7 cm(3) depending upon the configuration of an experiment. The DCD allows simultaneous measurement of boundary stresses on the packing and permeability of the packing to fluid flow. Visualization of the packing at compressive stress levels up to sigma(A)=7100 psi (49 MPa) is also demonstrated. The stresses measured are the normal stress at both walls on the axis of compression, with their difference providing a measure of the shear (or friction) force from the walls, and the transverse normal stress on one orthogonal axis, sigma(T). Permeability may be determined by either a fixed pressure drop or fixed flow rate experiment, with results presented from the fixed pressure drop approach by imposing a small gravity head of the flowing liquid; liquid flow is gravimetrically measured. The behaviors of packings of hard particles, both uncoated and when coated with a very viscous and tacky polyamide resin. are reported. The packing materials include a ceramic material used as a proppant in hydraulic fracturing of petroleum wells, and glass beads. The proppant and glass beads have mean diameters of approximately 700 mu m and 500 mu m. respectively, with the proppant less spherical and more polydisperse than the glass beads. The proppant particles undergo only limited breakage up to the maximum stress imposed here. The glass beads undergo significant breakage. Protocols for the compression can be varied. The reported results use a single loading and unloading at the same speed in each segment (increasing and decreasing stress), as well as a cyclic loading of differing numbers of cycles. The rate of loading is specified and can be varied from 0.56 mu m/s-1.7 mm/s, with results here focusing on the range of 1-30 mu m/s. Measured stress and permeability are shown as a function of axial load and loading rate, as well as the behavior in cyclic loading. The results are shown to be highly reproducible, establishing the ability to determine the properties of a proppant pack in a small charge device with imposed deformation. The influence of the resin coating on the properties is reported. Direct visualization is one of the key features of the DCD. Local motions and overall rearrangements of particles can be monitored by digital camera. These have been presented using particle image velocimetry (PIV).
- 出版日期2009-4
